Boulder Fall Ejecta: Present Day Activity on Mars

• Published in: Geophysical research letters Vol. 49; no. 1
• Main Authors: Vijayan, S., Harish, Kimi, K. B., Tuhi, S., Vigneshwaran, K., Sinha, R. K., Conway, S. J., Sivaraman, B., Bhardwaj, Anil
• Format: Journal Article
• Language: English
• Published: Washington John Wiley & Sons, Inc 16.01.2022; American Geophysical Union
• Subjects: Archives; boulder; Boulders; craters; Earth Sciences; Ejecta; Falls; Image analysis; Image processing; Mars; Mars surface; Planetary surfaces; Planetology; Sciences of the Universe; Surface activity; Surveying; Weathering
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2021GL096808

Boulder falls are an archives of recent surface activity on Mars, however, determining how recently they fell remains elusive. Our multitemporal HiRISE image analysis shows that new tracks are characterized by a herringbone‐like ejecta pattern at each boulder bounce that we call boulder fall ejecta (BFE). First systematic survey of BFE revealed ∼4,500 tracks whose total integrated track length is ∼900 km. Our BFE longevity analysis reveals that these tracks likely formed in the last few decades. From few examples we also observed slope streaks originating from BFE tracks, providing additional evidence favoring a dry origin theory. BFE fade in as little as ∼2 to 4 Mars years, whereas, others can persist >6 Mars years suggesting differential weathering. Nearly 30% of BFE are observed in the Cerberus Fossae region, which suggests it is one of the most seismically active regions. Thus, BFE can be used to recognize very recent surface processes on planetary surfaces. Plain Language Summary High‐resolution images of Mars have revealed numerous boulder falls on the surface. Here, we systematically surveyed images from 2006 to 2020 to find recent boulder falls which have ejecta. The images of the same place taken at different times, revealed that all new boulder falls have ejecta which we call boulder fall ejecta (BFE). We searched all the images and found BFE present in large numbers suggesting recent falls are common and widespread. Our results revealed that on Mars it takes ∼2 to 4 Mars years (4–8 Earth years) for BFE to disappear, whereas on Earth BFE are rarely preserved. We found that the Cerberus Fossae region adjacent to NASA's InSight lander landing site hosts nearly 30% of BFE, suggesting it is a currently active regions on Mars. Key Points Comprehensive multitemporal HiRISE image analysis revealed all new boulder falls have ejecta along the track termed as boulder fall ejecta (BFE) Approximately 4,500 tracks with total integrated length of ∼900 km formed in last few decades, 30% BFE located in Cerberus Fossae suggests active region Some BFE fade within 2–4 Mars year and few persist >6 Mars year, evidence for slope streaks originating from BFE tracks support dry theory