Perseverance Rover Uncovers Evidence of Repeated Asteroid Impacts in Ancient Martian Rock Layers

NASA’s Perseverance Mars rover has identified a 245-foot-thick (75-meter-thick) sequence of layered bedrock on the rim of Jezero Crater, termed the “Broom Point member,” which was formed by repeated asteroid impacts over 3.9 billion years ago. This discovery, published in the Journal of Geophysical Research: Planets, provides critical insights into one of the solar system’s most chaotic periods.

According to Ken Farley, Perseverance’s deputy project scientist at Caltech, the rover is now exploring a previously unexamined era of Martian geology. Unlike Earth, where plate tectonics have erased ancient records, Mars’ stagnant crust preserves these layers, offering a unique opportunity to study planetary history predating the crater itself.

Following its late 2024 ascent from Jezero Crater, Perseverance analyzed nearby rock formations and detected six distinct types of bedrock, including breccias with angular fragments and fine-grained, pulverized layers. Some breccias contain gas-bubble cavities, suggesting they originated from molten material. Glassy beads found in the strata further support an impact origin, as their abundance and size rival those from Earth’s Chicxulub asteroid event.

Alex Jones, a planetary geology Ph.D. student at Imperial College London and lead author of the study, explained that the rock layers reflect debris from impacts of varying sizes and distances. Some layers hint at water or ice interaction, resembling fast-moving debris flows that occur when molten rock encounters water on Earth. However, the extreme tilting of certain layers—up to 80 degrees—cannot be attributed to Jezero Crater’s formation, prompting scientists to propose a dual impact scenario.

They suggest an early massive asteroid impact created the 1,200-mile-wide (1,900-kilometer-wide) Isidis Basin, tilting the original rock layers. A subsequent, smaller impact formed Jezero Crater, fracturing and uplifting the pre-tilted strata into the structures observed today. Two core samples, Bell Island and Main River, have been collected to enable future Earth-based dating, potentially revealing the frequency of impacts during early Mars’ history—and by extension, the early Earth’s lost geological record.

Jones likened the layered record to a “cosmic weather report,” capturing billions of years of molten rock and dust deposition. If analyzed, these samples could illuminate how planetary surfaces evolved during a time when asteroid bombardment dominated the inner solar system.

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