The 3.9 billion-year-old cosmic record preserved on Mars

Space · Published 11 October 2026 Swipe more like this →

In short: While Earth's geological history has been erased by plate tectonics, Mars holds a pristine archive of the solar system's most violent era. Recent findings from the Perseverance rover reveal a massive, layered stack of rock built by repeated asteroid impacts.

On the rim of Jezero Crater, the Perseverance rover has uncovered the 'Broom Point member,' a 75-meter-thick (245-foot) sequence of ancient bedrock. Exceeding 3.9 billion years in age, this geological formation represents some of the most ancient ground studied by a rover. Because Mars lacks the plate tectonics that recycle and deform Earth's crust, this ancient record remains intact, offering a rare window into a period of history that has been lost on our own planet.

The structure of this rock sequence was shaped by a cosmic 'one-two punch.' Scientists believe a massive asteroid impact first created the 1,900-kilometer-wide (1,200-mile) Isidis Basin, an event powerful enough to tilt the once-flat rock layers to angles exceeding 80 degrees. Later, a second impact formed the 45-kilometer-wide (28-mile) Jezero Crater. The layers themselves consist of six distinct rock types, including breccias—rocks made of angular fragments—alternating with fine-grained, pulverized dust.

The primary architects of this landscape were repeated, high-energy asteroid impacts. Small, dark, vitreous spheres found inside these strata serve as vital proof; although volcanic activity creates comparable droplets, their extreme frequency suggests impacts. Some of these beads are as large as those produced by the Chicxulub asteroid that famously impacted Earth. These layers may also suggest an interaction with water or ice, as some features resemble fast, ground-hugging debris flows created when molten rock hits ice or water.

This discovery adds to the long legacy of Martian exploration. While the Opportunity rover, which landed on January 24, 2004, provided vital evidence of ancient wet environments, the Perseverance mission is now pushing into even older frontiers, exploring the geological history that predates the formation of Jezorb Crater itself.

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