Mars Wind Vibrations Reveal Subsurface Layering

New seismic data from Mars' Elysium Planitia region, collected by NASA's InSight mission, has revealed a complex subsurface structure, including a shallow sedimentary layer between lava flows. The findings, published in Nature Communications, were led by Dr. Cédric Schmelzbach from ETH Zurich, with contributions from researchers at the University of Cologne's Seismic Observatory.

The study focused on the shallow subsurface, up to 200 meters deep. Researchers identified a three-meter-thick layer of sandy regolith, followed by a 15-meter layer of coarse blocky ejecta. Below that, they found 150 meters of basaltic rock, consistent with expectations. However, a 30- to 40-meter-thick layer with low seismic velocity was discovered at a depth of about 30 meters, suggesting the presence of weak sedimentary materials.

To determine the age of the lava flows, the team used crater counting. They found that the shallower lava flows are approximately 1.7 billion years old, dating back to the Amazonian period, while the deeper basalt layer is around 3.6 billion years old, from the Hesperian period. The intermediate layer may consist of sedimentary deposits between these basalt layers or within the Amazonian basalts.

The findings offer the first direct comparison between seismic measurements and previous orbital predictions. Dr. Brigitte Knapmeyer-Endrun, a co-author, noted that these results could improve future mission planning by refining subsurface predictions. The data also helps assess the region's suitability for rovers and potential for water or ice. Sebastian Carrasco, a doctoral researcher at the University of Cologne, will continue analyzing how the shallow structure affects Marsquake recordings.