Seismic noise recorded at the surface of Mars has been monitored since February 2019, using the InSight seismometers. This noise can reach −200 dB. It is 500 times lower than on Earth at night and it increases of 30 dB during the day. We analyze its polarization as a function of time and frequency in the band 0.03–1 Hz. We use the degree of polarization to extract signals with stable polarization independent of their amplitude and type of polarization. We detect polarized signals at all frequencies and all times. Glitches correspond to linear polarized signals which are more abundant during the night. For signals with elliptical polarization, the ellipse is in the horizontal plane below 0.3 Hz. In the 0.3‐1Hz high frequency band (HF) and except in the evening, the ellipse is in the vertical plane and the major axis is tilted. While polarization azimuths are different in the two frequency bands, they both vary as a function of local hour and season. They are also correlated with wind direction, particularly during the daytime. We investigate possible aseismic and seismic origins of the polarized signals. Lander or tether noise can be discarded. Pressure fluctuations transported by wind may explain part of the HF polarization but not the tilt of the ellipse. This tilt can be obtained if the source is an acoustic emission coming from high altitude at critical angle. Finally, in the evening when the wind is low, the measured polarized signals may correspond to the seismic wavefield of the Mars background noise.

中文翻译：

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火星环境噪声的极化

自2019年2月以来，使用InSight地震仪对火星表面记录的地震噪声进行了监测。该噪声可以达到-200 dB。它比夜晚的地球低500倍，白天则增加30 dB。我们分析其极化随时间和频率在0.03-1 Hz范围内的变化。我们使用极化程度来提取具有稳定极化的信号，而与信号的振幅和极化类型无关。我们在所有频率和所有时间检测极化信号。毛刺对应于线性极化信号，该信号在夜间更为丰富。对于具有椭圆极化的信号，椭圆位于低于0.3 Hz的水平面中。在0.3-1Hz的高频段（HF）中，除晚上外，椭圆处于垂直平面，主轴线倾斜。尽管两个频带中的极化方位角不同，但它们都随当地小时和季节而变化。它们也与风向相关，尤其是在白天。我们研究了极化信号的可能的地震和地震起源。着陆器或系链噪声可以被丢弃。风传播的压力波动可能解释了部分HF极化，但不能解释椭圆的倾斜。如果源是来自临界角高海拔的声发射，则可以获得此倾斜。最终，在低风的傍晚，测得的极化信号可能对应于火星背景噪声的地震波场。特别是在白天。我们研究了极化信号的可能的地震和地震起源。着陆器或系链噪声可以被丢弃。风传播的压力波动可能解释了部分HF极化，但不能解释椭圆的倾斜。如果源是来自临界角高海拔的声发射，则可以获得此倾斜。最终，在低风的傍晚，测得的极化信号可能对应于火星背景噪声的地震波场。特别是在白天。我们研究了极化信号的可能的地震和地震起源。着陆器或系链噪声可以被丢弃。风传播的压力波动可能解释了部分HF极化，但不能解释椭圆的倾斜。如果源是来自临界角高海拔的声发射，则可以获得此倾斜。最终，在低风的傍晚，测得的极化信号可能对应于火星背景噪声的地震波场。如果源是来自临界角高海拔的声发射，则可以获得此倾斜。最后，在低风的傍晚，测得的极化信号可能对应于火星背景噪声的地震波场。如果源是来自临界角高海拔的声发射，则可以获得此倾斜。最终，在低风的傍晚，测得的极化信号可能对应于火星背景噪声的地震波场。