Recurring slope lineae (RSL) are dark linear markings on Mars that regrow annually and likely originate from the flow of either liquid water or granular material. Following the great dust storm (or planet‐encircling dust event, PEDE) of Mars year (MY) 34, Mars Reconnaissance Orbiter/High Resolution Imaging Science Experiment has seen many more candidate RSL than in typical Mars years. They have been imaged at more than 285 unique locations from August 2018 (when the atmosphere was clearing as the PEDE decayed) to August 2019, about half (157) of which are locations where RSL have not been documented previously. In MY34, 150 active RSL sites were identified in the southern middle latitudes (SML, ‐60° to ‐30°), whereas an average of 36 active sites were observed in each previous year (MY28–33). Post‐PEDE RSL are also present during southern summer over a wider range of latitude, slope aspect, and L_s (areocentric longitude of the sun) than in prior years. These RSL sites usually show evidence for recent dust deposition: obscuration of relatively dark areas, an overall brighter and redder surface than in prior years, and dust devil tracks, which indicate dust lifting by several mechanisms. We speculate that dust‐lifting processes may initiate and sustain RSL activity. The RSL may form from flows of dust (perhaps clumped) and/or sand that is destabilized by dust movement or directly mobilized by dust devils. If this is the case, then the otherwise puzzling recurrence and year‐to‐year variability of RSL activity can be at least partly explained. The dust replenishment varies from year to year, which could explain interannual variations in RSL activity.

中文翻译：

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火星：2018年行星环绕尘埃事件（PEDE）之后，大量反复出现的斜坡Lineae（RSL）

重复坡度线（RSL）是火星上的深色线性标记，每年重新生长，并且很可能源于液态水或颗粒状物质的流动。在火星年（MY）34发生沙尘暴（或环绕地球的尘埃事件，PEDE）之后，火星侦察轨道/高分辨率成像科学实验发现的候选RSL比典型的火星年多得多。从2018年8月（当PEDE腐烂时大气层逐渐消散）到2019年8月，它们已经在285个以上的独特位置成像，其中大约一半（157）是以前未记录RSL的位置。在MY34中，在中南纬度（SML，-60°至-30°）中发现了150个活动RSL站点，而在前一年（MY28-33）中平均观察到了36个活动站点。L _s（太阳的地心经度）比往年大。这些RSL站点通常显示最近尘埃沉积的证据：相对较暗的区域被遮盖，表面比往年更明亮和更红，并且尘埃魔鬼的踪迹表明尘埃通过多种机制扬起。我们推测扬尘过程可能引发并维持RSL活动。RSL可能是由尘埃流动（可能结块）和/或沙尘形成的，这些尘埃和尘埃由于尘埃运动而不稳定或直接由尘土飞散而流动。如果是这种情况，那么至少可以部分解释RSL活动的其他令人费解的复发和逐年变化。灰尘补充每年不同，这可以解释RSL活动的年际变化。