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  • The DREAMS Experiment Onboard the Schiaparelli Module of the ExoMars 2016 Mission: Design, Performances and Expected Results
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-08-20
    F. Esposito, S. Debei, C. Bettanini, C. Molfese, I. Arruego Rodríguez, G. Colombatti, A.-M. Harri, F. Montmessin, C. Wilson, A. Aboudan, P. Schipani, L. Marty, F. J. Álvarez, V. Apestigue, G. Bellucci, J.-J. Berthelier, J. R. Brucato, S. B. Calcutt, S. Chiodini, F. Cortecchia, F. Cozzolino, F. Cucciarrè, N. Deniskina, G. Déprez, G. Di Achille, F. Ferri, F. Forget, G. Franzese, E. Friso, M. Genzer, R. Hassen-Kodja, H. Haukka, M. Hieta, J. J. Jiménez, J.-L. Josset, H. Kahanpää, O. Karatekin, G. Landis, L. Lapauw, R. Lorenz, J. Martinez-Oter, V. Mennella, D. Möhlmann, D. Moirin, R. Molinaro, T. Nikkanen, E. Palomba, M. R. Patel, J.-P. Pommereau, C. I. Popa, S. Rafkin, P. Rannou, N. O. Renno, J. Rivas, W. Schmidt, E. Segato, S. Silvestro, A. Spiga, D. Toledo, R. Trautner, F. Valero, L. Vázquez, F. Vivat, O. Witasse, M. Yela, R. Mugnuolo, E. Marchetti, S. Pirrotta

    The first of the two missions foreseen in the ExoMars program was successfully launched on 14th March 2016. It included the Trace Gas Orbiter and the Schiaparelli Entry descent and landing Demonstrator Module. Schiaparelli hosted the DREAMS instrument suite that was the only scientific payload designed to operate after the touchdown. DREAMS is a meteorological station with the capability of measuring the electric properties of the Martian atmosphere. It was a completely autonomous instrument, relying on its internal battery for the power supply. Even with low resources (mass, energy), DREAMS would be able to perform novel measurements on Mars (atmospheric electric field) and further our understanding of the Martian environment, including the dust cycle. DREAMS sensors were designed to operate in a very dusty environment, because the experiment was designed to operate on Mars during the dust storm season (October 2016 in Meridiani Planum). Unfortunately, the Schiaparelli module failed part of the descent and the landing and crashed onto the surface of Mars. Nevertheless, several seconds before the crash, the module central computer switched the DREAMS instrument on, and sent back housekeeping data indicating that the DREAMS sensors were performing nominally. This article describes the instrument in terms of scientific goals, design, working principle and performances, as well as the results of calibration and field tests. The spare model is mature and available to fly in a future mission.

    更新日期:2018-08-20
  • Venus Atmospheric Thermal Structure and Radiative Balance
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-08-13
    Sanjay S. Limaye, Davide Grassi, Arnaud Mahieux, Alessandra Migliorini, Silvia Tellmann, Dmitrij Titov

    From the discovery that Venus has an atmosphere during the 1761 transit by M. Lomonosov to the current exploration of the planet by the Akatsuki orbiter, we continue to learn about the planet’s extreme climate and weather. This chapter attempts to provide a comprehensive but by no means exhaustive review of the results of the atmospheric thermal structure and radiative balance since the earlier works published in Venus and Venus II books from recent spacecraft and Earth based investigations and summarizes the gaps in our current knowledge. There have been no in-situ measurements of the deep Venus atmosphere since the flights of the two VeGa balloons and landers in 1985 (Sagdeev et al., Science 231:1411–1414, 1986). Thus, most of the new information about the atmospheric thermal structure has come from different remote sensing (Earth based and spacecraft) techniques using occultations (solar infrared, stellar ultraviolet and orbiter radio occultations), spectroscopy and microwave, short wave and thermal infrared emissions. The results are restricted to altitudes higher than about 40 km, except for one investigation of the near surface static stability inferred by Meadows and Crisp (J. Geophys. Res. 101:4595–4622, 1996) from 1 \(\upmu\)m observations from Earth. Little information about the lower atmospheric structure is possible below about 40 km altitude from radio occultations due to large bending angles. The gaps in our knowledge include spectral albedo variations over time, vertical variation of the bulk composition of the atmosphere (mean molecular weight), the identity, properties and abundances of absorbers of incident solar radiation in the clouds. The causes of opacity variations in the nightside cloud cover and vertical gradients in the deep atmosphere bulk composition and its impact on static stability are also in need of critical studies. The knowledge gaps and questions about Venus and its atmosphere provide the incentive for obtaining the necessary measurements to understand the planet, which can provide some clues to learn about terrestrial exoplanets.

    更新日期:2018-08-13
  • The Rotation and Interior Structure Experiment on the InSight Mission to Mars
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-08-09
    William M. Folkner, Véronique Dehant, Sébastien Le Maistre, Marie Yseboodt, Attilio Rivoldini, Tim Van Hoolst, Sami W. Asmar, Matthew P. Golombek

    The Rotation and Interior Structure Experiment (RISE) on-board the InSight mission will use the lander’s X-band (8 GHz) radio system in combination with tracking stations of the NASA Deep Space Network (DSN) to determine the rotation of Mars. RISE will measure the nutation of the Martian spin axis, detecting for the first time the effect of the liquid core of Mars and providing in turn new constraints on the core radius and density. RISE will also measure changes in the rotation rate of Mars on seasonal time-scales thereby constraining the atmospheric angular momentum budget. Finally, RISE will provide a superb tie between the cartographic and inertial reference frames. This paper describes the RISE scientific objectives and measurements, and provides the expected results of the experiment.

    更新日期:2018-08-10
  • Transforming Dust to Planets
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-08-09
    Francis Nimmo, Katherine Kretke, Shigeru Ida, Soko Matsumura, Thorsten Kleine

    We review recent progress in understanding how nebular dust and gas are converted into the planets of the present-day solar system, focusing particularly on the “Grand Tack” and pebble accretion scenarios. The Grand Tack can explain the observed division of the solar system into two different isotopic “flavours”, which are found in both differentiated and undifferentiated meteorites. The isotopic chronology inferred for the development of these two “flavours” is consistent with expectations of gas-giant growth and nebular gas loss timescales. The Grand Tack naturally makes a small Mars and a depleted, dynamically-excited and compositionally mixed asteroid belt (as observed); it builds both Mars and the Earth rapidly, which is consistent with the isotopically-inferred growth timescale of the former, but not the latter. Pebble accretion can explain the rapid required growth of Jupiter and Saturn, and the number of Kuiper Belt binaries, but requires specific assumptions to explain the relatively protracted growth timescale of Earth. Pure pebble accretion cannot explain the mixing observed in the asteroid belt, the fast proto-Earth spin rate, or the tilt of Uranus. No current observation requires pebble accretion to have operated in the inner solar system, but the thermal and compositional consequences of pebble accretion have yet to be explored in detail.

    更新日期:2018-08-10
  • Global Non-Potential Magnetic Models of the Solar Corona During the March 2015 Eclipse
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-08-08
    Anthony R. Yeates, Tahar Amari, Ioannis Contopoulos, Xueshang Feng, Duncan H. Mackay, Zoran Mikić, Thomas Wiegelmann, Joseph Hutton, Christopher A. Lowder, Huw Morgan, Gordon Petrie, Laurel A. Rachmeler, Lisa A. Upton, Aurelien Canou, Pierre Chopin, Cooper Downs, Miloslav Druckmüller, Jon A. Linker, Daniel B. Seaton, Tibor Török

    Seven different models are applied to the same problem of simulating the Sun’s coronal magnetic field during the solar eclipse on 2015 March 20. All of the models are non-potential, allowing for free magnetic energy, but the associated electric currents are developed in significantly different ways. This is not a direct comparison of the coronal modelling techniques, in that the different models also use different photospheric boundary conditions, reflecting the range of approaches currently used in the community. Despite the significant differences, the results show broad agreement in the overall magnetic topology. Among those models with significant volume currents in much of the corona, there is general agreement that the ratio of total to potential magnetic energy should be approximately 1.4. However, there are significant differences in the electric current distributions; while static extrapolations are best able to reproduce active regions, they are unable to recover sheared magnetic fields in filament channels using currently available vector magnetogram data. By contrast, time-evolving simulations can recover the filament channel fields at the expense of not matching the observed vector magnetic fields within active regions. We suggest that, at present, the best approach may be a hybrid model using static extrapolations but with additional energization informed by simplified evolution models. This is demonstrated by one of the models.

    更新日期:2018-08-10
  • Dust Phenomena Relating to Airless Bodies
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-08-07
    J. R. Szalay, A. R. Poppe, J. Agarwal, D. Britt, I. Belskaya, M. Horányi, T. Nakamura, M. Sachse, F. Spahn

    Airless bodies are directly exposed to ambient plasma and meteoroid fluxes, making them characteristically different from bodies whose dense atmospheres protect their surfaces from such fluxes. Direct exposure to plasma and meteoroids has important consequences for the formation and evolution of planetary surfaces, including altering chemical makeup and optical properties, generating neutral gas and/or dust exospheres, and leading to the generation of circumplanetary and interplanetary dust grain populations. In the past two decades, there have been many advancements in our understanding of airless bodies and their interaction with various dust populations. In this paper, we describe relevant dust phenomena on the surface and in the vicinity of airless bodies over a broad range of scale sizes from \(\sim10^{-3}~\mbox{km}\) to \(\sim10^{3}~\mbox{km}\), with a focus on recent developments in this field.

    更新日期:2018-08-07
  • ExoMars 2016 Schiaparelli Module Trajectory and Atmospheric Profiles Reconstruction
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-08-06
    A. Aboudan, G. Colombatti, C. Bettanini, F. Ferri, S. Lewis, B. Van Hove, O. Karatekin, S. Debei

    On 19th October 2016 Schiaparelli module of the ExoMars 2016 mission flew through the Mars atmosphere. After successful entry and descent under parachute, the module failed the last part of the descent and crashed on the Mars surface. Nevertheless the data transmitted in real-time by Schiaparelli during the entry and descent, together with the entry state vector as initial condition, have been used to reconstruct both the trajectory and the profiles of atmospheric density, pressure and temperature along the traversed path.

    更新日期:2018-08-06
  • The Heat Flow and Physical Properties Package (HP 3 ) for the InSight Mission
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-08-02
    T. Spohn, M. Grott, S. E. Smrekar, J. Knollenberg, T. L. Hudson, C. Krause, N. Müller, J. Jänchen, A. Börner, T. Wippermann, O. Krömer, R. Lichtenheldt, L. Wisniewski, J. Grygorczuk, M. Fittock, S. Rheershemius, T. Spröwitz, E. Kopp, I. Walter, A. C. Plesa, D. Breuer, P. Morgan, W. B. Banerdt

    The Heat Flow and Physical Properties Package HP3 for the InSight mission will attempt the first measurement of the planetary heat flow of Mars. The data will be taken at the InSight landing site in Elysium planitia (136 ∘E, 5 ∘N) and the uncertainty of the measurement aimed for shall be better than ±5 mW m−2. The package consists of a mechanical hammering device called the “Mole” for penetrating into the regolith, an instrumented tether which the Mole pulls into the ground, a fixed radiometer to determine the surface brightness temperature and an electronic box. The Mole and the tether are housed in a support structure before being deployed. The tether is equipped with 14 platinum resistance temperature sensors to measure temperature differences with a 1-\(\sigma \) uncertainty of 6.5 mK. Depth is determined by a tether length measurement device that monitors the amount of tether extracted from the support structure and a tiltmeter that measures the angle of the Mole axis to the local gravity vector. The Mole includes temperature sensors and heaters to measure the regolith thermal conductivity to better than 3.5% (1-\(\sigma \)) using the Mole as a modified line heat source. The Mole is planned to advance at least 3 m—sufficiently deep to reduce errors from daily surface temperature forcings—and up to 5 m into the martian regolith. After landing, HP3 will be deployed onto the martian surface by a robotic arm after choosing an instrument placement site that minimizes disturbances from shadows caused by the lander and the seismometer. The Mole will then execute hammering cycles, advancing 50 cm into the subsurface at a time, followed by a cooldown period of at least 48 h to allow heat built up during hammering to dissipate. After an equilibrated thermal state has been reached, a thermal conductivity measurement is executed for 24 h. This cycle is repeated until the final depth of 5 m is reached or further progress becomes impossible. The subsequent monitoring phase consists of hourly temperature measurements and lasts until the end of the mission. Model calculations show that the duration of temperature measurement required to sufficiently reduce the error introduced by annual surface temperature forcings is 0.6 martian years for a final depth of 3 m and 0.1 martian years for the target depth of 5 m.

    更新日期:2018-08-02
  • Influence of Body Waves, Instrumentation Resonances, and Prior Assumptions on Rayleigh Wave Ellipticity Inversion for Shallow Structure at the InSight Landing Site
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-07-30
    Brigitte Knapmeyer-Endrun, Naomi Murdoch, Balthasar Kenda, Matthew P. Golombek, Martin Knapmeyer, Lars Witte, Nicolas Verdier, Sharon Kedar, Philippe Lognonné, William B. Banerdt

    Based on an updated model of the regolith’s elastic properties, we simulate the ambient vibrations background wavefield recorded by InSight’s Seismic Experiment for Interior Structure (SEIS) on Mars to characterise the influence of the regolith and invert SEIS data for shallow subsurface structure. By approximately scaling the synthetics based on seismic signals of a terrestrial dust devil, we find that the high-frequency atmospheric background wavefield should be above the self-noise of SEIS’s SP sensors, even if the signals are not produced within 100–200 m of the station. We compare horizontal-to-vertical spectral ratios and Rayleigh wave ellipticity curves for a surface-wave based simulation on the one hand with synthetics explicitly considering body waves on the other hand and do not find any striking differences. Inverting the data, we find that the results are insensitive to assumptions on density. By contrast, assumptions on the velocity range in the upper-most layer have a strong influence on the results also at larger depth. Wrong assumptions can lead to results far from the true model in this case. Additional information on the general shape of the curve, i.e. single or dual peak, could help to mitigate this effect, even if it cannot directly be included into the inversion. We find that the ellipticity curves can provide stronger constraints on the minimum thickness and velocity of the second layer of the model than on the maximum values. We also consider the effect of instrumentation resonances caused by the lander flexible modes, solar panels, and the SEIS levelling system. Both the levelling system resonances and the lander flexible modes occur at significantly higher frequencies than the expected structural response, i.e. above 35 Hz and 20 Hz, respectively. While the lander and solar panel resonances might be too weak in amplitude to be recorded by SEIS, the levelling system resonances will show up clearly in horizontal spectra, the H/V and ellipticity curves. They are not removed by trying to extract only Rayleigh-wave dominated parts of the data. However, they can be distinguished from any subsurface response by their exceptionally low damping ratios of 1% or less as determined by random decrement analysis. The same applies to lander-generated signals observed in actual data from a Moon analogue experiment, so we expect this analysis will be useful in identifying instrumentation resonances in SEIS data.

    更新日期:2018-07-30
  • InSight Mars Lander Robotics Instrument Deployment System
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-07-30
    A. Trebi-Ollennu, Won Kim, Khaled Ali, Omair Khan, Cristina Sorice, Philip Bailey, Jeffrey Umland, Robert Bonitz, Constance Ciarleglio, Jennifer Knight, Nicolas Haddad, Kerry Klein, Scott Nowak, Daniel Klein, Nicholas Onufer, Kenneth Glazebrook, Brad Kobeissi, Enrique Baez, Felix Sarkissian, Menooa Badalian, Hallie Abarca, Robert G. Deen, Jeng Yen, Steven Myint, Justin Maki, Ali Pourangi, Jonathan Grinblat, Brian Bone, Noah Warner, Jaime Singer, Joan Ervin, Justin Lin

    The InSight Mars Lander is equipped with an Instrument Deployment System (IDS) and science payload with accompanying auxiliary peripherals mounted on the Lander. The InSight science payload includes a seismometer (SEIS) and Wind and Thermal Shield (WTS), heat flow probe (Heat Flow and Physical Properties Package, HP3) and a precision tracking system (RISE) to measure the size and state of the core, mantle and crust of Mars. The InSight flight system is a close copy of the Mars Phoenix Lander and comprises a Lander, cruise stage, heatshield and backshell. The IDS comprises an Instrument Deployment Arm (IDA), scoop, five finger “claw” grapple, motor controller, arm-mounted Instrument Deployment Camera (IDC), lander-mounted Instrument Context Camera (ICC), and control software. IDS is responsible for the first precision robotic instrument placement and release of SEIS and HP3 on a planetary surface that will enable scientists to perform the first comprehensive surface-based geophysical investigation of Mars’ interior structure. This paper describes the design and operations of the Instrument Deployment Systems (IDS), a critical subsystem of the InSight Mars Lander necessary to achieve the primary scientific goals of the mission including robotic arm geology and physical properties (soil mechanics) investigations at the Landing site. In addition, we present test results of flight IDS Verification and Validation activities including thermal characterization and InSight 2017 Assembly, Test, and Launch Operations (ATLO), Deployment Scenario Test at Lockheed Martin, Denver, where all the flight payloads were successfully deployed with a balloon gravity offload fixture to compensate for Mars to Earth gravity.

    更新日期:2018-07-30
  • Isolation of Seismic Signal from InSight/SEIS-SP Microseismometer Measurements
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-07-30
    J. Hurley, N. Murdoch, N. A. Teanby, N. Bowles, T. Warren, S. B. Calcutt, D. Mimoun, W. T. Pike

    The InSight mission is due to launch in May 2018, carrying a payload of novel instruments designed and tested to probe the interior of Mars whilst deployed directly on the Martian regolith and partially isolated from the Martian environment by the Wind and Thermal Shield. Central to this payload is the seismometry package SEIS consisting of two seismometers, which is supported by a suite of environmental/meteorological sensors (Temperature and Wind Sensor for InSight TWINS; and Auxiliary Payload Sensor Suite APSS). In this work, an optimal estimations inversion scheme which aims to decorrelate the short-period seismometer (SEIS-SP) signal due to seismic activity alone from the environmental signal and random noise is detailed, and tested on both simulated and Viking data. This scheme also applies a module to identify measurements contaminated by Single Event Phenomena (SEP). This scheme will be deployed as the pre-processing pipeline for all SEIS-SP data prior to release to the scientific community for analysis.

    更新日期:2018-07-30
  • Water and Volatile Inventories of Mercury, Venus, the Moon, and Mars
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-07-26
    James P. Greenwood, Shun-ichiro Karato, Kathleen E. Vander Kaaden, Kaveh Pahlevan, Tomohiro Usui

    We review the geochemical observations of water, \(\mbox{D}/\mbox{H}\) and volatile element abundances of the inner Solar System bodies, Mercury, Venus, the Moon, and Mars. We focus primarily on the inventories of water in these bodies, but also consider other volatiles when they can inform us about water. For Mercury, we have no data for internal water, but the reducing nature of the surface of Mercury would suggest that some hydrogen may be retained in its core. We evaluate the current knowledge and understanding of venusian water and volatiles and conclude that the venusian mantle was likely endowed with as much water as Earth of which it retains a small but non-negligible fraction. Estimates of the abundance of the Moon’s internal water vary from Earth-like to one to two orders of magnitude more depleted. Cl, K, and Zn isotope anomalies for lunar samples argue that the giant impact left a unique geochemical fingerprint on the Moon, but not the Earth. For Mars, an early magma ocean likely generated a thick crust; this combined with a lack of crustal recycling mechanisms would have led to early isolation of the Martian mantle from later delivery of water and volatiles from surface reservoirs or late accretion. The abundance estimates of Martian mantle water are similar to those of the terrestrial mantle, suggesting some similarities in the water and volatile inventories for the terrestrial planets and the Moon.

    更新日期:2018-07-26
  • Cosmological Distance Indicators
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-07-25
    Sherry H. Suyu, Tzu-Ching Chang, Frédéric Courbin, Teppei Okumura

    We review three distance measurement techniques beyond the local universe: (1) gravitational lens time delays, (2) baryon acoustic oscillation (BAO), and (3) HI intensity mapping. We describe the principles and theory behind each method, the ingredients needed for measuring such distances, the current observational results, and future prospects. Time-delays from strongly lensed quasars currently provide constraints on \(H_{0}\) with \(<4\%\) uncertainty, and with \(1\%\) within reach from ongoing surveys and efforts. Recent exciting discoveries of strongly lensed supernovae hold great promise for time-delay cosmography. BAO features have been detected in redshift surveys up to \(z\lesssim0.8\) with galaxies and \(z\sim2\) with Ly-\(\alpha\) forest, providing precise distance measurements and \(H_{0}\) with \(<2\%\) uncertainty in flat \(\Lambda\)CDM. Future BAO surveys will probe the distance scale with percent-level precision. HI intensity mapping has great potential to map BAO distances at \(z\sim0.8\) and beyond with precisions of a few percent. The next years ahead will be exciting as various cosmological probes reach \(1\%\) uncertainty in determining \(H_{0}\), to assess the current tension in \(H_{0}\) measurements that could indicate new physics.

    更新日期:2018-07-25
  • Future of Venus Research and Exploration
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-07-23
    Lori S. Glaze, Colin F. Wilson, Liudmila V. Zasova, Masato Nakamura, Sanjay Limaye

    Despite the tremendous progress that has been made since the publication of the Venus II book in 1997, many fundamental questions remain concerning Venus’ history, evolution and current geologic and atmospheric processes. The international science community has taken several approaches to prioritizing these questions, either through formal processes like the Planetary Decadal Survey in the United States and the Cosmic Vision in Europe, or informally through science definition teams utilized by Japan, Russia, and India. These questions are left to future investigators to address through a broad range of research approaches that include Earth-based observations, laboratory and modeling studies that are based on existing data, and new space flight missions. Many of the highest priority questions for Venus can be answered with new measurements acquired by orbiting or in situ missions that use current technologies, and several plausible implementation concepts have been studied and proposed for flight. However, observations needed to address some science questions pose substantial technological challenges, for example, long term survival on the surface of Venus and missions that require surface or controlled aerial mobility. Missions enabled by investments in these technologies will open the door to completely new ways of exploring Venus to provide unique insights into Venus’s past and the processes at work today.

    更新日期:2018-07-24
  • Impact of Distance Determinations on Galactic Structure. II. Old Tracers
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-07-23
    Andrea Kunder, Elena Valenti, Massimo Dall’Ora, Pawel Pietrukowicz, Chris Sneden, Giuseppe Bono, Vittorio F. Braga, Ivan Ferraro, Giuliana Fiorentino, Giacinto Iannicola, Marcella Marconi, Clara E. Martínez-Vázquez, Matteo Monelli, Ilaria Musella, Vincenzo Ripepi, Maurizio Salaris, Peter B. Stetson

    Here we review the efforts of a number of recent results that use old tracers to understand the build up of the Galaxy. Details that lead directly to using these old tracers to measure distances are discussed. We concentrate on the following: (1) the structure and evolution of the Galactic bulge and inner Galaxy constrained from the dynamics of individual stars residing therein; (2) the spatial structure of the old Galactic bulge through photometric observations of RR Lyrae-type stars; (3) the three-dimensional structure, stellar density, mass, chemical composition, and age of the Milky Way bulge as traced by its old stellar populations; (4) an overview of RR Lyrae stars known in the ultra-faint dwarfs and their relation to the Galactic halo; and (5) different approaches for estimating absolute and relative cluster ages.

    更新日期:2018-07-24
  • Venus Interior Structure and Dynamics
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-07-16
    Suzanne E. Smrekar, Anne Davaille, Christophe Sotin

    No two rocky bodies offer a better laboratory for exploring the conditions controlling interior dynamics than Venus and Earth. Their similarities in size, density, distance from the sun, and young surfaces would suggest comparable interior dynamics. Although the two planets exhibit some of the same processes, Venus lacks Earth’s dominant process for losing heat and cycling volatiles between the interior and the surface and atmosphere: plate tectonics. One commonality is the size and number of mantle plume features which are inferred to be active today and arise at the core mantle boundary. Such mantle plumes require heat loss from the core, yet Venus lacks a measurable interior dynamo. There is evidence for plume-induced subduction on Venus, but no apparent mosaic of moving plates. Absent plate tectonics, one essential question for interior dynamics is how did Venus obtain its young resurfacing age? Via catastrophic or equilibrium processes? Related questions are how does it lose heat via past periods of plate tectonics, has it always had a stagnant lid, or might it have an entirely different mode of heat loss? Although there has been no mission dedicated to surface and interior processes since the Magellan mission in 1990, near infrared surface emissivity data that provides information on the iron content of the surface mineralogy was obtained fortuitously from Venus Express. These data imply both the presence of continental-like crust, and thus formation in the presence of water, and recent volcanism at mantle hotspots. In addition, the study of interior dynamics for both Earth and exoplanets has led to new insights on the conditions required to initiate subduction and develop plate tectonics, including the possible role of high temperature lithosphere, and a renewed drive to reveal why Venus and Earth differ. Here we review current data that constrains the interior dynamics of Venus, new insights into its interior dynamics, and the data needed to resolve key questions.

    更新日期:2018-07-16
  • Models for Type Ia Supernovae and Related Astrophysical Transients
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-04-30
    Friedrich K. Röpke, Stuart A. Sim

    We give an overview of recent efforts to model Type Ia supernovae and related astrophysical transients resulting from thermonuclear explosions in white dwarfs. In particular we point out the challenges resulting from the multi-physics multi-scale nature of the problem and discuss possible numerical approaches to meet them in hydrodynamical explosion simulations and radiative transfer modeling. We give examples of how these methods are applied to several explosion scenarios that have been proposed to explain distinct subsets or, in some cases, the majority of the observed events. In case we comment on some of the successes and shortcoming of these scenarios and highlight important outstanding issues.

    更新日期:2018-07-14
  • Kelvin–Helmholtz Instability: Lessons Learned and Ways Forward
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-04-24
    A. Masson, K. Nykyri

    The Kelvin–Helmholtz instability (KHI) is a ubiquitous phenomenon across the Universe, observed from 500 m deep in the oceans on Earth to the Orion molecular cloud. Over the past two decades, several space missions have enabled a leap forward in our understanding of this phenomenon at the Earth’s magnetopause. Key results obtained by these missions are first presented, with a special emphasis on Cluster and THEMIS. In particular, as an ideal instability, the KHI was not expected to produce mass transport. Simulations, later confirmed by spacecraft observations, indicate that plasma transport in Kelvin–Helmholtz (KH) vortices can arise during non-linear stage of its development via secondary process. In addition to plasma transport, spacecraft observations have revealed that KHI can also lead to significant ion heating due to enhanced ion-scale wave activity driven by the KHI. Finally, we describe what are the upcoming observational opportunities in 2018–2020, thanks to a unique constellation of multi-spacecraft missions including: MMS, Cluster, THEMIS, Van Allen Probes and Swarm.

    更新日期:2018-07-14
  • Peculiar Supernovae
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-04-17
    Dan Milisavljevic, Raffaella Margutti

    What makes a supernova truly “peculiar?” In this review we attempt to address this question by tracing the history of the use of “peculiar” as a descriptor of non-standard supernovae back to the original binary spectroscopic classification of Type I vs. Type II proposed by Minkowski (Publ. Astron. Soc. Pac., 53:224, 1941). A handful of noteworthy examples are highlighted to illustrate a general theme: classes of supernovae that were once thought to be peculiar are later seen as logical branches of standard events. This is not always the case, however, and we discuss ASASSN-15lh as an example of a transient with an origin that remains contentious. We remark on how late-time observations at all wavelengths (radio-through-X-ray) that probe 1) the kinematic and chemical properties of the supernova ejecta and 2) the progenitor star system’s mass loss in the terminal phases preceding the explosion, have often been critical in understanding the nature of seemingly unusual events.

    更新日期:2018-07-14
  • Single Degenerate Models for Type Ia Supernovae: Progenitor’s Evolution and Nucleosynthesis Yields
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-04-17
    Ken’ichi Nomoto, Shing-Chi Leung

    We review how the single degenerate models for Type Ia supernovae (SNe Ia) works. In the binary star system of a white dwarf (WD) and its non-degenerate companion star, the WD accretes either hydrogen-rich matter or helium and undergoes hydrogen and helium shell-burning. We summarize how the stability and non-linear behavior of such shell-burning depend on the accretion rate and the WD mass and how the WD blows strong wind. We identify the following evolutionary routes for the accreting WD to trigger a thermonuclear explosion. Typically, the accretion rate is quite high in the early stage and gradually decreases as a result of mass transfer. With decreasing rate, the WD evolves as follows: (1) At a rapid accretion phase, the WD increase its mass by stable H burning and blows a strong wind to keep its moderate radius. The wind is strong enough to strip a part of the companion star’s envelope to control the accretion rate and forms circumstellar matter (CSM). If the WD explodes within CSM, it is observed as an “SN Ia-CSM”. (X-rays emitted by the WD are absorbed by CSM.) (2) If the WD continues to accrete at a lower rate, the wind stops and an SN Ia is triggered under steady-stable H shell-burning, which is observed as a super-soft X-ray source: “SN Ia-SSXS”. (3) If the accretion continues at a still lower rate, H shell-burning becomes unstable and many flashes recur. The WD undergoes recurrent nova (RN) whose mass ejection is smaller than the accreted matter. Then the WD evolves to an “SN Ia-RN”. (4) If the companion is a He star (or a He WD), the accretion of He can trigger He and C double detonations at the sub-Chandrasekhar mass or the WD grows to the Chandrasekhar mass while producing a He-wind: “SN Ia-He CSM”. (5) If the accreting WD rotates quite rapidly, the WD mass can exceed the Chandrasekhar mass of the spherical WD, which delays the trigger of an SN Ia. After angular momentum is lost from the WD, the (super-Chandra) WD contracts to become a delayed SN Ia. The companion star has become a He WD and CSM has disappeared: “SN Ia-He WD”. We update nucleosynthesis yields of the carbon deflagration model W7, delayed detonation model WDD2, and the sub-Chandrasekhar mass model to provide some constraints on the yields (such as Mn) from the comparison with the observations. We note the important metallicity effects on 58Ni and 55Mn.

    更新日期:2018-07-14
  • Inferring Nighttime Ionospheric Parameters with the Far Ultraviolet Imager Onboard the Ionospheric Connection Explorer
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-04-17
    Farzad Kamalabadi, Jianqi Qin, Brian J. Harding, Dimitrios Iliou, Jonathan J. Makela, R. R. Meier, Scott L. England, Harald U. Frey, Stephen B. Mende, Thomas J. Immel

    The Ionospheric Connection Explorer (ICON) Far Ultraviolet (FUV) imager, ICON FUV, will measure altitude profiles of OI 135.6 nm emissions to infer nighttime ionospheric parameters. Accurate estimation of the ionospheric state requires the development of a comprehensive radiative transfer model from first principles to quantify the effects of physical processes on the production and transport of the 135.6 nm photons in the ionosphere including the mutual neutralization contribution as well as the effect of resonant scattering by atomic oxygen and pure absorption by oxygen molecules. This forward model is then used in conjunction with a constrained optimization algorithm to invert the anticipated ICON FUV line-of-sight integrated measurements. In this paper, we describe the connection between ICON FUV measurements and the nighttime ionosphere, along with the approach to inverting the measured emission profiles to derive the associated O+ profiles from 150–450 km in the nighttime ionosphere that directly reflect the electron density in the F-region of the ionosphere.

    更新日期:2018-07-14
  • Fine Resolution Epithermal Neutron Detector (FREND) Onboard the ExoMars Trace Gas Orbiter
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-07-11
    I. Mitrofanov, A. Malakhov, B. Bakhtin, D. Golovin, A. Kozyrev, M. Litvak, M. Mokrousov, A. Sanin, V. Tretyakov, A. Vostrukhin, A. Anikin, L. M. Zelenyi, J. Semkova, S. Malchev, B. Tomov, Y. Matviichuk, P. Dimitrov, R. Koleva, T. Dachev, K. Krastev, V. Shvetsov, G. Timoshenko, Y. Bobrovnitsky, T. Tomilina, V. Benghin, V. Shurshakov

    ExoMars is a two-launch mission undertaken by Roscosmos and European Space Agency. Trace Gas Orbiter, a satellite part of the 2016 launch carries the Fine Resolution Neutron Detector instrument as part of its payload. The instrument aims at mapping hydrogen content in the upper meter of Martian soil with spatial resolution between 60 and 200 km diameter spot. This resolution is achieved by a collimation module that limits the field of view of the instruments detectors. A dosimetry module that surveys the radiation environment in cruise to Mars and on orbit around it is another part of the instrument.

    更新日期:2018-07-12
  • The OSIRIS-REx Thermal Emission Spectrometer (OTES) Instrument
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-07-11
    P. R. Christensen, V. E. Hamilton, G. L. Mehall, D. Pelham, W. O’Donnell, S. Anwar, H. Bowles, S. Chase, J. Fahlgren, Z. Farkas, T. Fisher, O. James, I. Kubik, I. Lazbin, M. Miner, M. Rassas, L. Schulze, K. Shamordola, T. Tourville, G. West, R. Woodward, D. Lauretta

    The OSIRIS-REx Thermal Emission Spectrometer (OTES) will provide remote measurements of mineralogy and thermophysical properties of Bennu to map its surface, help select the OSIRIS-REx sampling site, and investigate the Yarkovsky effect. OTES is a Fourier Transform spectrometer covering the spectral range 5.71–100 μm (\(1750\mbox{--}100~\mbox{cm}^{-1}\)) with a spectral sample interval of \(8.66~\mbox{cm}^{-1}\) and a 6.5-mrad field of view. The OTES telescope is a 15.2-cm diameter Cassegrain telescope that feeds a flat-plate Michelson moving mirror mounted on a linear voice-coil motor assembly. A single uncooled deuterated l-alanine doped triglycine sulfate (DLATGS) pyroelectric detector is used to sample the interferogram every two seconds. Redundant ∼0.855 μm laser diodes are used in a metrology interferometer to provide precise moving mirror control and IR sampling at 772 Hz. The beamsplitter is a 38-mm diameter, 1-mm thick chemical vapor deposited diamond with an antireflection microstructure to minimize surface reflection. An internal calibration cone blackbody target provides radiometric calibration. The radiometric precision in a single spectrum is \(\leq2.2 \times 10^{-8}~\mbox{W}\,\mbox{cm}^{-2}\,\mbox{sr} ^{-1}/\mbox{cm}^{-1}\) between 300 and \(1350~\mbox{cm}^{-1}\). The absolute integrated radiance error is \(<1\%\) for scene temperatures ranging from 150 to 380 K. The overall OTES envelope size is \(37.5 \times 28.9 \times 52.2~\mbox{cm}\), and the mass is 6.27 kg. The power consumption is 10.8 W average. OTES was developed by Arizona State University with Moog Broad Reach developing the electronics. OTES was integrated, tested, and radiometrically calibrated on the Arizona State University campus in Tempe, AZ.

    更新日期:2018-07-12
  • Near-Field Seismic Propagation and Coupling Through Mars’ Regolith: Implications for the InSight Mission
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-07-09
    R. Myhill, N. A. Teanby, J. Wookey, N. Murdoch

    NASA’s InSight Mission will deploy two three-component seismometers on Mars in 2018. These short period and very broadband seismometers will be mounted on a three-legged levelling system, which will sit directly on the sandy regolith some 2–3 meters from the lander. Although the deployment will be covered by a wind and thermal shield, atmospheric noise is still expected to couple to the seismometers through the regolith. Seismic activity on Mars is expected to be significantly lower than on Earth, so a characterisation of the extent of coupling to noise and seismic signals is an important step towards maximising scientific return.

    更新日期:2018-07-09
  • Geology and Physical Properties Investigations by the InSight Lander
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-06-26
    M. Golombek, M. Grott, G. Kargl, J. Andrade, J. Marshall, N. Warner, N. A. Teanby, V. Ansan, E. Hauber, J. Voigt, R. Lichtenheldt, B. Knapmeyer-Endrun, I. J. Daubar, D. Kipp, N. Muller, P. Lognonné, C. Schmelzbach, D. Banfield, A. Trebi-Ollennu, J. Maki, S. Kedar, D. Mimoun, N. Murdoch, S. Piqueux, P. Delage, W. T. Pike, C. Charalambous, R. Lorenz, L. Fayon, A. Lucas, S. Rodriguez, P. Morgan, A. Spiga, M. Panning, T. Spohn, S. Smrekar, T. Gudkova, R. Garcia, D. Giardini, U. Christensen, T. Nicollier, D. Sollberger, J. Robertsson, K. Ali, B. Kenda, W. B. Banerdt

    Although not the prime focus of the InSight mission, the near-surface geology and physical properties investigations provide critical information for both placing the instruments (seismometer and heat flow probe with mole) on the surface and for understanding the nature of the shallow subsurface and its effect on recorded seismic waves. Two color cameras on the lander will obtain multiple stereo images of the surface and its interaction with the spacecraft. Images will be used to identify the geologic materials and features present, quantify their areal coverage, help determine the basic geologic evolution of the area, and provide ground truth for orbital remote sensing data. A radiometer will measure the hourly temperature of the surface in two spots, which will determine the thermal inertia of the surface materials present and their particle size and/or cohesion. Continuous measurements of wind speed and direction offer a unique opportunity to correlate dust devils and high winds with eolian changes imaged at the surface and to determine the threshold friction wind stress for grain motion on Mars. During the first two weeks after landing, these investigations will support the selection of instrument placement locations that are relatively smooth, flat, free of small rocks and load bearing. Soil mechanics parameters and elastic properties of near surface materials will be determined from mole penetration and thermal conductivity measurements from the surface to 3–5 m depth, the measurement of seismic waves during mole hammering, passive monitoring of seismic waves, and experiments with the arm and scoop of the lander (indentations, scraping and trenching). These investigations will determine and test the presence and mechanical properties of the expected 3–17 m thick fragmented regolith (and underlying fractured material) built up by impact and eolian processes on top of Hesperian lava flows and determine its seismic properties for the seismic investigation of Mars’ interior.

    更新日期:2018-06-27
  • Crustal S-Wave Velocity from Apparent Incidence Angles: A Case Study in Preparation for InSight
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-06-26
    Brigitte Knapmeyer-Endrun, Savas Ceylan, Martin van Driel

    Retrieval of crustal structure and thickness of Mars is among the main goals of InSight. Here we investigate which constraints on the crust at the landing site can be provided by apparent P-wave incidence angles derived from P-receiver functions. We consider receiver functions for six different Mars models, calculated from synthetic seismograms generated via Instaseis from the Green’s function databases of the Marsquake Service, in detail. To allow for a larger range of crustal thicknesses and structures, we additionally analyze data from five broad-band stations across Central Europe. We find that the likely usable epicentral distance range for P-wave receiver functions on Mars lies between \(35^{\circ}\) and the core shadow, and can be extended to more than \(150^{\circ}\) by also using the PP-phase. Comparison to models for the spatial distribution of Martian seismicity indicates that sufficient seismicity should occur within the P-wave distance range around InSight within the nominal mission duration to allow for the application of our method. Apparent P-wave incidence angles are derived from the amplitudes of vertical and radial receiver functions at the P-wave onset within a range of period bands, up to 120 s. The apparent incidence angles are directly related to apparent S-wave velocities, which are inverted for the subsurface S-wave velocity structure via a grid search. The veracity of the forward calculated receiver functions and apparent S-wave velocities is ensured by benchmarking various algorithms against the Instaseis synthetics. Results indicate that apparent S-wave velocity curves provide valuable constraints on crustal thickness and structure, even without any additional constraints, and considering the location uncertainty and limited data quantity of InSight. S-wave velocities in the upper half of the crust are constrained best, but if reliable measurements at long periods are available, the curves also provide constraints down to the uppermost mantle. Besides, it is demonstrated that the apparent velocity curves can differentiate between crustal velocity models that are indistinguishable by other methods.

    更新日期:2018-06-27
  • Electron Power-Law Spectra in Solar and Space Plasmas
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-06-25
    M. Oka, J. Birn, M. Battaglia, C. C. Chaston, S. M. Hatch, G. Livadiotis, S. Imada, Y. Miyoshi, M. Kuhar, F. Effenberger, E. Eriksson, Y. V. Khotyaintsev, A. Retinò

    Particles are accelerated to very high, non-thermal energies in solar and space plasma environments. While energy spectra of accelerated electrons often exhibit a power law, it remains unclear how electrons are accelerated to high energies and what processes determine the power-law index \(\delta \). Here, we review previous observations of the power-law index \(\delta \) in a variety of different plasma environments with a particular focus on sub-relativistic electrons. It appears that in regions more closely related to magnetic reconnection (such as the ‘above-the-looptop’ solar hard X-ray source and the plasma sheet in Earth’s magnetotail), the spectra are typically soft (\(\delta \gtrsim 4\)). This is in contrast to the typically hard spectra (\(\delta \lesssim 4\)) that are observed in coincidence with shocks. The difference implies that shocks are more efficient in producing a larger non-thermal fraction of electron energies when compared to magnetic reconnection. A caveat is that during active times in Earth’s magnetotail, \(\delta \) values seem spatially uniform in the plasma sheet, while power-law distributions still exist even in quiet times. The role of magnetotail reconnection in the electron power-law formation could therefore be confounded with these background conditions. Because different regions have been studied with different instrumentations and methodologies, we point out a need for more systematic and coordinated studies of power-law distributions for a better understanding of possible scaling laws in particle acceleration as well as their universality.

    更新日期:2018-06-27
  • Jets Downstream of Collisionless Shocks
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-06-21
    Ferdinand Plaschke, Heli Hietala, Martin Archer, Xóchitl Blanco-Cano, Primož Kajdič, Tomas Karlsson, Sun Hee Lee, Nojan Omidi, Minna Palmroth, Vadim Roytershteyn, Daniel Schmid, Victor Sergeev, David Sibeck

    The magnetosheath flow may take the form of large amplitude, yet spatially localized, transient increases in dynamic pressure, known as “magnetosheath jets” or “plasmoids” among other denominations. Here, we describe the present state of knowledge with respect to such jets, which are a very common phenomenon downstream of the quasi-parallel bow shock. We discuss their properties as determined by satellite observations (based on both case and statistical studies), their occurrence, their relation to solar wind and foreshock conditions, and their interaction with and impact on the magnetosphere. As carriers of plasma and corresponding momentum, energy, and magnetic flux, jets bear some similarities to bursty bulk flows, which they are compared to. Based on our knowledge of jets in the near Earth environment, we discuss the expectations for jets occurring in other planetary and astrophysical environments. We conclude with an outlook, in which a number of open questions are posed and future challenges in jet research are discussed.

    更新日期:2018-06-22
  • NOMAD, an Integrated Suite of Three Spectrometers for the ExoMars Trace Gas Mission: Technical Description, Science Objectives and Expected Performance
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-06-19
    A. C. Vandaele, J.-J. Lopez-Moreno, M. R. Patel, G. Bellucci, F. Daerden, B. Ristic, S. Robert, I. R. Thomas, V. Wilquet, M. Allen, G. Alonso-Rodrigo, F. Altieri, S. Aoki, D. Bolsée, T. Clancy, E. Cloutis, C. Depiesse, R. Drummond, A. Fedorova, V. Formisano, B. Funke, F. González-Galindo, A. Geminale, J.-C. Gérard, M. Giuranna, L. Hetey, N. Ignatiev, J. Kaminski, O. Karatekin, Y. Kasaba, M. Leese, F. Lefèvre, S. R. Lewis, M. López-Puertas, M. López-Valverde, A. Mahieux, J. Mason, J. McConnell, M. Mumma, L. Neary, E. Neefs, E. Renotte, J. Rodriguez-Gomez, G. Sindoni, M. Smith, A. Stiepen, A. Trokhimovsky, J. Vander Auwera, G. Villanueva, S. Viscardy, J. Whiteway, Y. Willame, M. Wolff, the NOMAD Team

    The NOMAD (“Nadir and Occultation for MArs Discovery”) spectrometer suite on board the ExoMars Trace Gas Orbiter (TGO) has been designed to investigate the composition of Mars’ atmosphere, with a particular focus on trace gases, clouds and dust. The detection sensitivity for trace gases is considerably improved compared to previous Mars missions, compliant with the science objectives of the TGO mission. This will allow for a major leap in our knowledge and understanding of the Martian atmospheric composition and the related physical and chemical processes. The instrument is a combination of three spectrometers, covering a spectral range from the UV to the mid-IR, and can perform solar occultation, nadir and limb observations. In this paper, we present the science objectives of the instrument and explain the technical principles of the three spectrometers. We also discuss the expected performance of the instrument in terms of spatial and temporal coverage and detection sensitivity.

    更新日期:2018-06-19
  • Imaging Plasma Density Structures in the Soft X-Rays Generated by Solar Wind Charge Exchange with Neutrals
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-06-12
    David G. Sibeck, R. Allen, H. Aryan, D. Bodewits, P. Brandt, G. Branduardi-Raymont, G. Brown, J. A. Carter, Y. M. Collado-Vega, M. R. Collier, H. K. Connor, T. E. Cravens, Y. Ezoe, M.-C. Fok, M. Galeazzi, O. Gutynska, M. Holmström, S.-Y. Hsieh, K. Ishikawa, D. Koutroumpa, K. D. Kuntz, M. Leutenegger, Y. Miyoshi, F. S. Porter, M. E. Purucker, A. M. Read, J. Raeder, I. P. Robertson, A. A. Samsonov, S. Sembay, S. L. Snowden, N. E. Thomas, R. von Steiger, B. M. Walsh, S. Wing

    Both heliophysics and planetary physics seek to understand the complex nature of the solar wind’s interaction with solar system obstacles like Earth’s magnetosphere, the ionospheres of Venus and Mars, and comets. Studies with this objective are frequently conducted with the help of single or multipoint in situ electromagnetic field and particle observations, guided by the predictions of both local and global numerical simulations, and placed in context by observations from far and extreme ultraviolet (FUV, EUV), hard X-ray, and energetic neutral atom imagers (ENA). Each proposed interaction mechanism (e.g., steady or transient magnetic reconnection, local or global magnetic reconnection, ion pick-up, or the Kelvin-Helmholtz instability) generates diagnostic plasma density structures. The significance of each mechanism to the overall interaction (as measured in terms of atmospheric/ionospheric loss at comets, Venus, and Mars or global magnetospheric/ionospheric convection at Earth) remains to be determined but can be evaluated on the basis of how often the density signatures that it generates are observed as a function of solar wind conditions. This paper reviews efforts to image the diagnostic plasma density structures in the soft (low energy, 0.1–2.0 keV) X-rays produced when high charge state solar wind ions exchange electrons with the exospheric neutrals surrounding solar system obstacles.

    更新日期:2018-06-12
  • ExoMars Trace Gas Orbiter (TGO) Science Ground Segment (SGS)
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-06-12
    L. Metcalfe, M. Aberasturi, E. Alonso, R. Álvarez, M. Ashman, I. Barbarisi, J. Brumfitt, A. Cardesín, D. Coia, M. Costa, R. Fernández, D. Frew, J. Gallegos, J. J. García Beteta, B. Geiger, D. Heather, T. Lim, P. Martin, C. Muñoz Crego, M. Muñoz Fernandez, A. Villacorta, H. Svedhem

    The ExoMars Trace Gas Orbiter (TGO) Science Ground Segment (SGS), comprised of payload Instrument Team, ESA and Russian operational centres, is responsible for planning the science operations of the TGO mission and for the generation and archiving of the scientific data products to levels meeting the scientific aims and criteria specified by the ESA Project Scientist as advised by the Science Working Team (SWT). The ExoMars SGS builds extensively upon tools and experience acquired through earlier ESA planetary missions like Mars and Venus Express, and Rosetta, but also is breaking ground in various respects toward the science operations of future missions like BepiColombo or JUICE. A productive interaction with the Russian partners in the mission facilitates broad and effective collaboration. This paper describes the global organisation and operation of the SGS, with reference to its principal systems, interfaces and operational processes.

    更新日期:2018-06-12
  • Cometary Dust
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-03-28
    Anny-Chantal Levasseur-Regourd, Jessica Agarwal, Hervé Cottin, Cécile Engrand, George Flynn, Marco Fulle, Tamas Gombosi, Yves Langevin, Jérémie Lasue, Thurid Mannel, Sihane Merouane, Olivier Poch, Nicolas Thomas, Andrew Westphal

    This review presents our understanding of cometary dust at the end of 2017. For decades, insight about the dust ejected by nuclei of comets had stemmed from remote observations from Earth or Earth’s orbit, and from flybys, including the samples of dust returned to Earth for laboratory studies by the Stardust return capsule. The long-duration Rosetta mission has recently provided a huge and unique amount of data, obtained using numerous instruments, including innovative dust instruments, over a wide range of distances from the Sun and from the nucleus. The diverse approaches available to study dust in comets, together with the related theoretical and experimental studies, provide evidence of the composition and physical properties of dust particles, e.g., the presence of a large fraction of carbon in macromolecules, and of aggregates on a wide range of scales. The results have opened vivid discussions on the variety of dust-release processes and on the diversity of dust properties in comets, as well as on the formation of cometary dust, and on its presence in the near-Earth interplanetary medium. These discussions stress the significance of future explorations as a way to decipher the formation and evolution of our Solar System.

    更新日期:2018-06-03
  • Dust in Supernovae and Supernova Remnants I: Formation Scenarios
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-03-27
    A. Sarangi, M. Matsuura, E. R. Micelotta

    Supernovae are considered as prime sources of dust in space. Observations of local supernovae over the past couple of decades have detected the presence of dust in supernova ejecta. The reddening of the high redshift quasars also indicate the presence of large masses of dust in early galaxies. Considering the top heavy IMF in the early galaxies, supernovae are assumed to be the major contributor to these large amounts of dust. However, the composition and morphology of dust grains formed in a supernova ejecta is yet to be understood with clarity. Moreover, the dust masses inferred from observations in mid-infrared and submillimeter wavelength regimes differ by two orders of magnitude or more. Therefore, the mechanism responsible for the synthesis of molecules and dust in such environments plays a crucial role in studying the evolution of cosmic dust in galaxies. This review summarises our current knowledge of dust formation in supernova ejecta and tries to quantify the role of supernovae as dust producers in a galaxy.

    更新日期:2018-06-03
  • Nucleosynthesis in Supernovae
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-03-26
    Friedrich-Karl Thielemann, Jordi Isern, Albino Perego, Peter von Ballmoos

    We present the status and open problems of nucleosynthesis in supernova explosions of both types, responsible for the production of the intermediate mass, Fe-group and heavier elements (with the exception of the main s-process). Constraints from observations can be provided through individual supernovae (SNe) or their remnants (e.g. via spectra and gamma-rays of decaying unstable isotopes) and through surface abundances of stars which witness the composition of the interstellar gas at their formation. With a changing fraction of elements heavier than He in these stars (known as metallicity) the evolution of the nucleosynthesis in galaxies over time can be determined. A complementary way, related to gamma-rays from radioactive decays, is the observation of positrons released in \(\beta^{+}\)-decays, as e.g. from \(^{26}\mbox{Al}\), \(^{44}\mbox{Ti}\), \(^{56,57}\mbox{Ni}\) and possibly further isotopes of their decay chains (in competition with the production of \(e^{+}e^{-}\) pairs in acceleration shocks from SN remnants, pulsars, magnetars or even of particle physics origin). We discuss (a) the role of the core-collapse supernova explosion mechanism for the composition of intermediate mass, Fe-group (and heavier?) ejecta, (b) the transition from neutron stars to black holes as the final result of the collapse of massive stars, and the relation of the latter to supernovae, faint supernovae, and gamma-ray bursts/hypernovae, (c) Type Ia supernovae and their nucleosynthesis (e.g. addressing the \(^{55}\mbox{Mn}\) puzzle), plus (d) further constraints from galactic evolution, \(\gamma\)-ray and positron observations. This is complemented by the role of rare magneto-rotational supernovae (related to magnetars) in comparison with the nucleosynthesis of compact binary mergers, especially with respect to forming the heaviest r-process elements in galactic evolution.

    更新日期:2018-06-03
  • Abundances, Ionization States, Temperatures, and FIP in Solar Energetic Particles
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-03-23
    Donald V. Reames

    The relative abundances of chemical elements and isotopes have been our most effective tool in identifying and understanding the physical processes that control populations of energetic particles. The early surprise in solar energetic particles (SEPs) was 1000-fold enhancements in \({}^{3}\mbox{He}/{}^{4}\mbox{He}\) from resonant wave-particle interactions in the small “impulsive” SEP events that emit electron beams that produce type III radio bursts. Further studies found enhancements in Fe/O, then extreme enhancements in element abundances that increase with mass-to-charge ratio \(A/Q\), rising by a factor of 1000 from He to Au or Pb arising in magnetic reconnection regions on open field lines in solar jets. In contrast, in the largest SEP events, the “gradual” events, acceleration occurs at shock waves driven out from the Sun by fast, wide coronal mass ejections (CMEs). Averaging many events provides a measure of solar coronal abundances, but \(A/Q\)-dependent scattering during transport causes variations with time; thus if Fe scatters less than O, Fe/O is enhanced early and depleted later. To complicate matters, shock waves often reaccelerate impulsive suprathermal ions left over or trapped above active regions that have spawned many impulsive events. Direct measurements of ionization states \(Q\) show coronal temperatures of 1–2 MK for most gradual events, but impulsive events often show stripping by matter traversal after acceleration. Direct measurements of \(Q\) are difficult and often unavailable. Since both impulsive and gradual SEP events have abundance enhancements that vary as powers of \(A/Q\), we can use abundances to deduce the probable \(Q\)-values and the source plasma temperatures during acceleration, ≈3 MK for impulsive SEPs. This new technique also allows multiple spacecraft to measure temperature variations across the face of a shock wave, measurements otherwise unavailable and provides a new understanding of abundance variations in the element He. Comparing coronal abundances from SEPs and from the slow solar wind as a function of the first ionization potential (FIP) of the elements, remaining differences are for the elements C, P, and S. The theory of the fractionation of ions by Alfvén waves shows that C, P, and S are suppressed because of wave resonances during chromospheric transport on closed magnetic loops but not on open magnetic fields that supply the solar wind. Shock waves can accelerate ions from closed coronal loops that easily escape as SEPs, while the solar wind must emerge on open fields.

    更新日期:2018-06-03
  • From Disks to Planets: The Making of Planets and Their Early Atmospheres. An Introduction
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-03-14
    Helmut Lammer, Michel Blanc

    This paper is an introduction to volume 56 of the Space Science Series of ISSI, “From disks to planets—the making of planets and their proto-atmospheres”, a key subject in our quest for the origins and evolutionary paths of planets, and for the causes of their diversity. Indeed, as exoplanet discoveries progressively accumulated and their characterization made spectacular progress, it became evident that the diversity of observed exoplanets can in no way be reduced to the two classes of planets that we are used to identify in the solar system, namely terrestrial planets and gas or ice giants: the exoplanet reality is just much broader. This fact is no doubt the result of the exceptional diversity of the evolutionary paths linking planetary systems as a whole as well as individual exoplanets and their proto-atmospheres to their parent circumstellar disks: this diversity and its causes are exactly what this paper explores. For each of the main phases of the formation and evolution of planetary systems and of individual planets, we summarize what we believe we understand and what are the important open questions needing further in-depth examination, and offer some suggestions on ways towards solutions.

    更新日期:2018-06-03
  • Superluminous Supernovae
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-03-13
    Takashi J. Moriya, Elena I. Sorokina, Roger A. Chevalier

    Superluminous supernovae are a new class of supernovae that were recognized about a decade ago. Both observational and theoretical progress has been significant in the last decade. In this review, we first briefly summarize the observational properties of superluminous supernovae. We then introduce the three major suggested luminosity sources to explain the huge luminosities of superluminous supernovae, i.e., the nuclear decay of 56Ni, the interaction between supernova ejecta and dense circumstellar media, and the spin down of magnetars. We compare these models and discuss their strengths and weaknesses.

    更新日期:2018-06-03
  • Partially Ionized Plasmas in Astrophysics
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-03-13
    José Luis Ballester, Igor Alexeev, Manuel Collados, Turlough Downes, Robert F. Pfaff, Holly Gilbert, Maxim Khodachenko, Elena Khomenko, Ildar F. Shaikhislamov, Roberto Soler, Enrique Vázquez-Semadeni, Teimuraz Zaqarashvili

    Partially ionized plasmas are found across the Universe in many different astrophysical environments. They constitute an essential ingredient of the solar atmosphere, molecular clouds, planetary ionospheres and protoplanetary disks, among other environments, and display a richness of physical effects which are not present in fully ionized plasmas. This review provides an overview of the physics of partially ionized plasmas, including recent advances in different astrophysical areas in which partial ionization plays a fundamental role. We outline outstanding observational and theoretical questions and discuss possible directions for future progress.

    更新日期:2018-06-03
  • The New Horizons Kuiper Belt Extended Mission
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-05-09
    S. A. Stern, H. A. Weaver, J. R. Spencer, H. A. Elliott, the New Horizons Team

    The central objective of the New Horizons prime mission was to make the first exploration of Pluto and its system of moons. Following that, New Horizons has been approved for its first extended mission, which has the objectives of extensively studying the Kuiper Belt environment, observing numerous Kuiper Belt Objects (KBOs) and Centaurs in unique ways, and making the first close flyby of the KBO 486958 2014 MU69. This review summarizes the objectives and plans for this approved mission extension, and briefly looks forward to potential objectives for subsequent extended missions by New Horizons.

    更新日期:2018-05-09
  • Water Partitioning in Planetary Embryos and Protoplanets with Magma Oceans
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-05-08
    M. Ikoma, L. Elkins-Tanton, K. Hamano, J. Suckale

    The water content of magma oceans is widely accepted as a key factor that determines whether a terrestrial planet is habitable. Water ocean mass is determined as a result not only of water delivery and loss, but also of water partitioning among several reservoirs. Here we review our current understanding of water partitioning among the atmosphere, magma ocean, and solid mantle of accreting planetary embryos and protoplanets just after giant collisions. Magma oceans are readily formed in planetary embryos and protoplanets in their accretion phase. Significant amounts of water are partitioned into magma oceans, provided the planetary building blocks are water-rich enough. Particularly important but still quite uncertain issues are how much water the planetary building blocks contain initially and how water goes out of the solidifying mantle and is finally degassed to the atmosphere. Constraints from both solar-system explorations and exoplanet observations and also from laboratory experiments are needed to resolve these issues.

    更新日期:2018-05-08
  • The Multi-Needle Langmuir Probe System on Board NorSat-1
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-05-08
    H. Hoang, L. B. N. Clausen, K. Røed, T. A. Bekkeng, E. Trondsen, B. Lybekk, H. Strøm, D. M. Bang-Hauge, A. Pedersen, A. Spicher, J. I. Moen

    On July 14th, 2017, the first Norwegian scientific satellite NorSat-1 was launched into a high-inclination (98∘), low-Earth orbit (600 km altitude) from Baikonur, Kazakhstan. As part of the payload package, NorSat-1 carries the multi-needle Langmuir probe (m-NLP) instrument which is capable of sampling the electron density at a rate up to 1 kHz, thus offering an unprecedented opportunity to continuously resolve ionospheric plasma density structures down to a few meters. Over the coming years, NorSat-1 will cross the equatorial and polar regions twice every 90 minutes, providing a wealth of data that will help to better understand the mechanisms that dissipate energy input from larger spatial scales by creating small-scale plasma density structures within the ionosphere. In this paper we describe the m-NLP system on board NorSat-1 and present some first results from the instrument commissioning phase. We show that the m-NLP instrument performs as expected and highlight its unique capabilities at resolving small-scale ionospheric plasma density structures.

    更新日期:2018-05-08
  • Impact of Distance Determinations on Galactic Structure. I. Young and Intermediate-Age Tracers
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-05-01
    Noriyuki Matsunaga, Giuseppe Bono, Xiaodian Chen, Richard de Grijs, Laura Inno, Shogo Nishiyama

    Here we discuss impacts of distance determinations on the Galactic disk traced by relatively young objects. The Galactic disk, \(\sim40~\mbox{kpc}\) in diameter, is a cross-road of studies on the methods of measuring distances, interstellar extinction, evolution of galaxies, and other subjects of interest in astronomy. A proper treatment of interstellar extinction is, for example, crucial for estimating distances to stars in the disk outside the small range of the solar neighborhood. We’ll review the current status of relevant studies and discuss some new approaches to the extinction law. When the extinction law is reasonably constrained, distance indicators found in today and future surveys are telling us stellar distribution and more throughout the Galactic disk. Among several useful distance indicators, the focus of this review is Cepheids and open clusters (especially contact binaries in clusters). These tracers are particularly useful for addressing the metallicity gradient of the Galactic disk, an important feature for which comparison between observations and theoretical models can reveal the evolution of the disk.

    更新日期:2018-05-01
  • OSIRIS-REx Flight Dynamics and Navigation Design
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-04-17
    B. Williams, P. Antreasian, E. Carranza, C. Jackman, J. Leonard, D. Nelson, B. Page, D. Stanbridge, D. Wibben, K. Williams, M. Moreau, K. Berry, K. Getzandanner, A. Liounis, A. Mashiku, D. Highsmith, B. Sutter, D. S. Lauretta

    OSIRIS-REx is the first NASA mission to return a sample of an asteroid to Earth. Navigation and flight dynamics for the mission to acquire and return a sample of asteroid 101955 Bennu establish many firsts for space exploration. These include relatively small orbital maneuvers that are precise to ∼1 mm/s, close-up operations in a captured orbit about an asteroid that is small in size and mass, and planning and orbit phasing to revisit the same spot on Bennu in similar lighting conditions. After preliminary surveys and close approach flyovers of Bennu, the sample site will be scientifically characterized and selected. A robotic shock-absorbing arm with an attached sample collection head mounted on the main spacecraft bus acquires the sample, requiring navigation to Bennu’s surface. A touch-and-go sample acquisition maneuver will result in the retrieval of at least 60 grams of regolith, and up to several kilograms. The flight activity concludes with a return cruise to Earth and delivery of the sample return capsule (SRC) for landing and sample recovery at the Utah Test and Training Range (UTTR).

    更新日期:2018-04-17
  • Very Long Baseline Interferometry: Dependencies on Frequency Stability
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-04-05
    Axel Nothnagel, Tobias Nilsson, Harald Schuh

    Very Long Baseline Interferometry (VLBI) is a differential technique observing radiation of compact extra-galactic radio sources with pairs of radio telescopes. For these observations, the frequency standards at the telescopes need to have very high stability. In this article we discuss why this is, and we investigate exactly how precise the frequency standards need to be. Four areas where good clock performance is needed are considered: coherence, geodetic parameter estimation, correlator synchronization, and UT1 determination. We show that in order to ensure the highest accuracy of VLBI, stability similar to that of a hydrogen maser is needed for time-scales up to a few hours. In the article, we are considering both traditional VLBI where extra-galactic radio sources are observed, as well as observation of man-made artificial radio sources emitted by satellites or spacecrafts.

    更新日期:2018-04-06
  • Water Loss from Young Planets
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-04-04
    Feng Tian, Manuel Güdel, Colin P. Johnstone, Helmut Lammer, Rodrigo Luger, Petra Odert

    Good progress has been made in the past few years to better understand the XUV evolution trend of Sun-like stars, the capture and dissipation of hydrogen dominant envelopes of planetary embryos and protoplanets, and water loss from young planets around M dwarfs. This chapter reviews these recent developments. Observations of exoplanets and theoretical works in the near future will significantly advance our understanding of one of the fundamental physical processes shaping the evolution of solar system terrestrial planets.

    更新日期:2018-04-04
  • Type Ia Supernova Cosmology
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-03-12
    B. Leibundgut, M. Sullivan

    The primary agent for Type Ia supernova cosmology is the uniformity of their appearance. We present the current status, achievements and uncertainties. The Hubble constant and the expansion history of the universe are key measurements provided by Type Ia supernovae. They were also instrumental in showing time dilation, which is a direct observational signature of expansion. Connections to explosion physics are made in the context of potential improvements of the quality of Type Ia supernovae as distance indicators. The coming years will see large efforts to use Type Ia supernovae to characterise dark energy.

    更新日期:2018-03-12
  • Evolution of the Sunspot Number and Solar Wind B $B$ Time Series
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-03-08
    Edward W. Cliver, Konstantin Herbst

    The past two decades have witnessed significant changes in our knowledge of long-term solar and solar wind activity. The sunspot number time series (1700-present) developed by Rudolf Wolf during the second half of the 19th century was revised and extended by the group sunspot number series (1610–1995) of Hoyt and Schatten during the 1990s. The group sunspot number is significantly lower than the Wolf series before ∼1885. An effort from 2011–2015 to understand and remove differences between these two series via a series of workshops had the unintended consequence of prompting several alternative constructions of the sunspot number. Thus it has been necessary to expand and extend the sunspot number reconciliation process. On the solar wind side, after a decade of controversy, an ISSI International Team used geomagnetic and sunspot data to obtain a high-confidence time series of the solar wind magnetic field strength (\(B\)) from 1750-present that can be compared with two independent long-term (> ∼600 year) series of annual \(B\)-values based on cosmogenic nuclides. In this paper, we trace the twists and turns leading to our current understanding of long-term solar and solar wind activity.

    更新日期:2018-03-08
  • Order out of Randomness: Self-Organization Processes in Astrophysics
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-03-06
    Markus J. Aschwanden, Felix Scholkmann, William Béthune, Werner Schmutz, Valentina Abramenko, Mark C. M. Cheung, Daniel Müller, Arnold Benz, Guennadi Chernov, Alexei G. Kritsuk, Jeffrey D. Scargle, Andrew Melatos, Robert V. Wagoner, Virginia Trimble, William H. Green

    Self-organization is a property of dissipative nonlinear processes that are governed by a global driving force and a local positive feedback mechanism, which creates regular geometric and/or temporal patterns, and decreases the entropy locally, in contrast to random processes. Here we investigate for the first time a comprehensive number of (17) self-organization processes that operate in planetary physics, solar physics, stellar physics, galactic physics, and cosmology. Self-organizing systems create spontaneous “order out of randomness”, during the evolution from an initially disordered system to an ordered quasi-stationary system, mostly by quasi-periodic limit-cycle dynamics, but also by harmonic (mechanical or gyromagnetic) resonances. The global driving force can be due to gravity, electromagnetic forces, mechanical forces (e.g., rotation or differential rotation), thermal pressure, or acceleration of nonthermal particles, while the positive feedback mechanism is often an instability, such as the magneto-rotational (Balbus-Hawley) instability, the convective (Rayleigh-Bénard) instability, turbulence, vortex attraction, magnetic reconnection, plasma condensation, or a loss-cone instability. Physical models of astrophysical self-organization processes require hydrodynamic, magneto-hydrodynamic (MHD), plasma, or N-body simulations. Analytical formulations of self-organizing systems generally involve coupled differential equations with limit-cycle solutions of the Lotka-Volterra or Hopf-bifurcation type.

    更新日期:2018-03-07
  • Dust in Supernovae and Supernova Remnants II: Processing and Survival
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-03-05
    E. R. Micelotta, M. Matsuura, A. Sarangi

    Observations have recently shown that supernovae are efficient dust factories, as predicted for a long time by theoretical models. The rapid evolution of their stellar progenitors combined with their efficiency in precipitating refractory elements from the gas phase into dust grains make supernovae the major potential suppliers of dust in the early Universe, where more conventional sources like Asymptotic Giant Branch (AGB) stars did not have time to evolve. However, dust yields inferred from observations of young supernovae or derived from models do not reflect the net amount of supernova-condensed dust able to be expelled from the remnants and reach the interstellar medium. The cavity where the dust is formed and initially resides is crossed by the high velocity reverse shock which is generated by the pressure of the circumstellar material shocked by the expanding supernova blast wave. Depending on grain composition and initial size, processing by the reverse shock may lead to substantial dust erosion and even complete destruction. The goal of this review is to present the state of the art about processing and survival of dust inside supernova remnants, in terms of theoretical modelling and comparison to observations.

    更新日期:2018-03-06
  • The OSIRIS-REx Visible and InfraRed Spectrometer (OVIRS): Spectral Maps of the Asteroid Bennu
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-03-05
    D. C. Reuter, A. A. Simon, J. Hair, A. Lunsford, S. Manthripragada, V. Bly, B. Bos, C. Brambora, E. Caldwell, G. Casto, Z. Dolch, P. Finneran, D. Jennings, M. Jhabvala, E. Matson, M. McLelland, W. Roher, T. Sullivan, E. Weigle, Y. Wen, D. Wilson, D. S. Lauretta

    The OSIRIS-REx Visible and Infrared Spectrometer (OVIRS) is a point spectrometer covering the spectral range of 0.4 to 4.3 microns (25,000–2300 cm−1). Its primary purpose is to map the surface composition of the asteroid Bennu, the target asteroid of the OSIRIS-REx asteroid sample return mission. The information it returns will help guide the selection of the sample site. It will also provide global context for the sample and high spatial resolution spectra that can be related to spatially unresolved terrestrial observations of asteroids. It is a compact, low-mass (17.8 kg), power efficient (8.8 W average), and robust instrument with the sensitivity needed to detect a 5% spectral absorption feature on a very dark surface (3% reflectance) in the inner solar system (0.89–1.35 AU). It, in combination with the other instruments on the OSIRIS-REx Mission, will provide an unprecedented view of an asteroid’s surface.

    更新日期:2018-03-06
  • The IMISS-1 Experiment for Recording and Analysis of Accelerations in Orbital Flight
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-02-28
    V. A. Sadovnichii, V. V. Alexandrov, D. I. Bugrov, S. S. Lemak, V. B. Pakhomov, M. I. Panasyuk, V. L. Petrov, I. V. Yashin

    The IMISS-1 experiment represents the second step in solving the problem of the creation of the gaze stabilization corrector. This device is designed to correct the effect of the gaze stabilization delay under microgravity. IMISS-1 continues research started by the Tat’yana-2 satellite. This research will be continued on board the International Space Station. At this stage we study the possibility of registration of angular and linear accelerations acting on the sensitive mass in terms of Low Earth Orbit flight, using MEMS sensors.

    更新日期:2018-02-28
  • Dust Evolution in Protoplanetary Discs and the Formation of Planetesimals
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-02-28
    Jürgen Blum

    After 25 years of laboratory research on protoplanetary dust agglomeration, a consistent picture of the various processes that involve colliding dust aggregates has emerged. Besides sticking, bouncing and fragmentation, other effects, like, e.g., erosion or mass transfer, have now been extensively studied. Coagulation simulations consistently show that \(\upmu\mbox{m}\)-sized dust grains can grow to mm- to cm-sized aggregates before they encounter the bouncing barrier, whereas sub-\(\upmu\mbox{m}\)-sized water-ice particles can directly grow to planetesimal sizes. For siliceous materials, other processes have to be responsible for turning the dust aggregates into planetesimals. In this article, these processes are discussed, the physical properties of the emerging dusty or icy planetesimals are presented and compared to empirical evidence from within and without the Solar System. In conclusion, the formation of planetesimals by a gravitational collapse of dust “pebbles” seems the most likely.

    更新日期:2018-02-28
  • The Importance of Water for Life
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-02-20
    Frances Westall, André Brack

    Liquid water is essential for life as we know it, i.e. carbon-based life. Although other compound-solvent pairs that could exist in very specific physical environments could be envisaged, the elements essential to carbon and water-based life are among the most common in the universe. Carbon molecules and liquid water have physical and chemical properties that make them optimised compound-solvent pairs. Liquid water is essential for important prebiotic reactions. But equally important for the emergence of life is the contact of carbon molecules in liquid water with hot rocks and minerals. We here review the environmental conditions of the early Earth, as soon as it had liquid water at its surface and was habitable. Basing our approach to life as a “cosmic phenomenon” (de Duve 1995), i.e. a chemical continuum, we briefly address the various hypotheses for the origin of life, noting their relevance with respect to early environmental conditions. It appears that hydrothermal environments were important in this respect. We continue with the record of early life noting that, by 3.5 Ga, when the sedimentary environment started being well-preserved, anaerobic life forms had colonised all habitable microenvironments from the sea floor to exposed beach environments and, possibly, in the photic planktonic zone of the sea. Life on Earth had also evolved to the relatively sophisticated stage of anoxygenic photosynthesis. We conclude with an evaluation of the potential for habitability and colonisation of other planets and satellites in the Solar System, noting that the most common life forms in the Solar System and probably in the Universe would be similar to terrestrial chemotrophs whose carbon source is either reduced carbon or CO2 dissolved in water and whose energy would be sourced from oxidized carbon, H2, or other transition elements.

    更新日期:2018-02-21
  • Regolith X-Ray Imaging Spectrometer (REXIS) Aboard the OSIRIS-REx Asteroid Sample Return Mission
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-02-12
    R. A. Masterson, M. Chodas, L. Bayley, B. Allen, J. Hong, P. Biswas, C. McMenamin, K. Stout, E. Bokhour, H. Bralower, D. Carte, S. Chen, M. Jones, S. Kissel, F. Schmidt, M. Smith, G. Sondecker, L. F. Lim, D. S. Lauretta, J. E. Grindlay, R. P. Binzel

    The Regolith X-ray Imaging Spectrometer (REXIS) is the student collaboration experiment proposed and built by an MIT-Harvard team, launched aboard NASA’s OSIRIS-REx asteroid sample return mission. REXIS complements the scientific investigations of other OSIRIS-REx instruments by determining the relative abundances of key elements present on the asteroid’s surface by measuring the X-ray fluorescence spectrum (stimulated by the natural solar X-ray flux) over the range of energies 0.5 to 7 keV. REXIS consists of two components: a main imaging spectrometer with a coded aperture mask and a separate solar X-ray monitor to account for the Sun’s variability. In addition to element abundance ratios (relative to Si) pinpointing the asteroid’s most likely meteorite association, REXIS also maps elemental abundance variability across the asteroid’s surface using the asteroid’s rotation as well as the spacecraft’s orbital motion. Image reconstruction at the highest resolution is facilitated by the coded aperture mask. Through this operation, REXIS will be the first application of X-ray coded aperture imaging to planetary surface mapping, making this student-built instrument a pathfinder toward future planetary exploration. To date, 60 students at the undergraduate and graduate levels have been involved with the REXIS project, with the hands-on experience translating to a dozen Master’s and Ph.D. theses and other student publications.

    更新日期:2018-02-12
  • The Delivery of Water During Terrestrial Planet Formation
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-02-08
    David P. O’Brien, Andre Izidoro, Seth A. Jacobson, Sean N. Raymond, David C. Rubie

    The planetary building blocks that formed in the terrestrial planet region were likely very dry, yet water is comparatively abundant on Earth. Here we review the various mechanisms proposed for the origin of water on the terrestrial planets. Various in-situ mechanisms have been suggested, which allow for the incorporation of water into the local planetesimals in the terrestrial planet region or into the planets themselves from local sources, although all of those mechanisms have difficulties. Comets have also been proposed as a source, although there may be problems fitting isotopic constraints, and the delivery efficiency is very low, such that it may be difficult to deliver even a single Earth ocean of water this way. The most promising route for water delivery is the accretion of material from beyond the snow line, similar to carbonaceous chondrites, that is scattered into the terrestrial planet region as the planets are growing. Two main scenarios are discussed in detail. First is the classical scenario in which the giant planets begin roughly in their final locations and the disk of planetesimals and embryos in the terrestrial planet region extends all the way into the outer asteroid belt region. Second is the Grand Tack scenario, where early inward and outward migration of the giant planets implants material from beyond the snow line into the asteroid belt and terrestrial planet region, where it can be accreted by the growing planets. Sufficient water is delivered to the terrestrial planets in both scenarios. While the Grand Tack scenario provides a better fit to most constraints, namely the small mass of Mars, planets may form too fast in the nominal case discussed here. This discrepancy may be reduced as a wider range of initial conditions is explored. Finally, we discuss several more recent models that may have important implications for water delivery to the terrestrial planets.

    更新日期:2018-02-08
  • The Origin, Early Evolution and Predictability of Solar Eruptions
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-02-07
    Lucie M. Green, Tibor Török, Bojan Vršnak, Ward Manchester, Astrid Veronig

    Coronal mass ejections (CMEs) were discovered in the early 1970s when space-borne coronagraphs revealed that eruptions of plasma are ejected from the Sun. Today, it is known that the Sun produces eruptive flares, filament eruptions, coronal mass ejections and failed eruptions; all thought to be due to a release of energy stored in the coronal magnetic field during its drastic reconfiguration. This review discusses the observations and physical mechanisms behind this eruptive activity, with a view to making an assessment of the current capability of forecasting these events for space weather risk and impact mitigation. Whilst a wealth of observations exist, and detailed models have been developed, there still exists a need to draw these approaches together. In particular more realistic models are encouraged in order to asses the full range of complexity of the solar atmosphere and the criteria for which an eruption is formed. From the observational side, a more detailed understanding of the role of photospheric flows and reconnection is needed in order to identify the evolutionary path that ultimately means a magnetic structure will erupt.

    更新日期:2018-02-07
  • The OSIRIS-REx Radio Science Experiment at Bennu
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-02-06
    J. W. McMahon, D. J. Scheeres, S. G. Hesar, D. Farnocchia, S. Chesley, D. Lauretta

    The OSIRIS-REx mission will conduct a Radio Science investigation of the asteroid Bennu with a primary goal of estimating the mass and gravity field of the asteroid. The spacecraft will conduct proximity operations around Bennu for over 1 year, during which time radiometric tracking data, optical landmark tracking images, and altimetry data will be obtained that can be used to make these estimates. Most significantly, the main Radio Science experiment will be a 9-day arc of quiescent operations in a 1-km nominally circular terminator orbit. The pristine data from this arc will allow the Radio Science team to determine the significant components of the gravity field up to the fourth spherical harmonic degree. The Radio Science team will also be responsible for estimating the surface accelerations, surface slopes, constraints on the internal density distribution of Bennu, the rotational state of Bennu to confirm YORP estimates, and the ephemeris of Bennu that incorporates a detailed model of the Yarkovsky effect.

    更新日期:2018-02-06
  • The Morphologies and Kinematics of Supernova Remnants
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-02-06
    Laura A. Lopez, Robert A. Fesen

    We review the major advances in understanding the morphologies and kinematics of supernova remnants (SNRs). Simulations of SN explosions have improved dramatically over the last few years, and SNRs can be used to test models through comparison of predictions with SNRs’ observed large-scale compositional and morphological properties as well as the three-dimensional kinematics of ejecta material. In particular, Cassiopeia A—the youngest known core-collapse SNR in the Milky Way—offers an up-close view of the complexity of these explosive events that cannot be resolved in distant, extragalactic sources. We summarize the progress in tying SNRs to their progenitors’ explosions through imaging and spectroscopic observations, and we discuss exciting future prospects for SNR studies, such as X-ray microcalorimeters.

    更新日期:2018-02-06
  • Modelling Quasi-Periodic Pulsations in Solar and Stellar Flares
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-02-06
    J. A. McLaughlin, V. M. Nakariakov, M. Dominique, P. Jelínek, S. Takasao

    Solar flare emission is detected in all EM bands and variations in flux density of solar energetic particles. Often the EM radiation generated in solar and stellar flares shows a pronounced oscillatory pattern, with characteristic periods ranging from a fraction of a second to several minutes. These oscillations are referred to as quasi-periodic pulsations (QPPs), to emphasise that they often contain apparent amplitude and period modulation. We review the current understanding of quasi-periodic pulsations in solar and stellar flares. In particular, we focus on the possible physical mechanisms, with an emphasis on the underlying physics that generates the resultant range of periodicities. These physical mechanisms include MHD oscillations, self-oscillatory mechanisms, oscillatory reconnection/reconnection reversal, wave-driven reconnection, two loop coalescence, MHD flow over-stability, the equivalent LCR-contour mechanism, and thermal-dynamical cycles. We also provide a histogram of all QPP events published in the literature at this time. The occurrence of QPPs puts additional constraints on the interpretation and understanding of the fundamental processes operating in flares, e.g. magnetic energy liberation and particle acceleration. Therefore, a full understanding of QPPs is essential in order to work towards an integrated model of solar and stellar flares.

    更新日期:2018-02-06
  • Cosmic Ray Production in Supernovae
    Space Sci. Rev. (IF 9.327) Pub Date : 2018-01-30
    A. M. Bykov, D. C. Ellison, A. Marcowith, S. M. Osipov

    We give a brief review of the origin and acceleration of cosmic rays (CRs), emphasizing the production of CRs at different stages of supernova evolution by the first-order Fermi shock acceleration mechanism. We suggest that supernovae with trans-relativistic outflows, despite being rather rare, may accelerate CRs to energies above \(10^{18}\mbox{ eV}\) over the first year of their evolution. Supernovae in young compact clusters of massive stars, and interaction powered superluminous supernovae, may accelerate CRs well above the PeV regime. We discuss the acceleration of the bulk of the galactic CRs in isolated supernova remnants and re-acceleration of escaped CRs by the multiple shocks present in superbubbles produced by associations of OB stars. The effects of magnetic field amplification by CR driven instabilities, as well as superdiffusive CR transport, are discussed for nonthermal radiation produced by nonlinear shocks of all speeds including trans-relativistic ones.

    更新日期:2018-01-30
Some contents have been Reproduced with permission of the American Chemical Society.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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