NASA's Perseverance Rover Uncovers 4‑Billion‑Year‑Old Impact Evidence

When Perseverance rolled up onto the western edge of Jezero Crater in early 2025, the team at JPL expected more of the same dusty basalt. Instead, the rover’s cameras caught sight of a massive, oddly‑stacked wall of rock that looked almost engineered.

Dubbed the “Broom Point member” by the scientists, this formation is roughly 75 metres (about 245 feet) thick and composed of a dozen distinct layers. Each layer alternates between coarse, angular breccia fragments and fine, powdery dust – a pattern that, after close inspection, tells a story of repeated, high‑energy impacts.

In a paper just released in the Journal of Geophysical Research: Planets, researchers from Imperial College London argued that the stack likely dates back to the Late Heavy Bombardment, a turbulent window 4.1–3.8 billion years ago when the inner Solar System was pummeled by asteroids and comets. If their calculations are right, we’re looking at some of the oldest terrain ever examined by a rover.

Ken Farley, deputy project scientist for Perseverance, summed it up in a press release: “Mars doesn’t recycle its crust the way Earth does, so these ancient layers have survived in situ. It’s a bit like finding a pristine page in a very old book that on Earth would have been shredded.”

The rover’s instruments detected six separate rock types within the stack. Some of the breccia pieces contain tiny bubbles – little cavities that form when molten rock cools too quickly. Others host dark, glassy beads that only appear when material is melted by a massive impact or a volcanic blast. The largest beads are comparable in size to the glass shards ejected when the Chicxulub asteroid slammed into Earth and ended the age of dinosaurs.

What’s striking is how many of these layers are tilted almost straight up – some at angles exceeding 80 degrees. That steepness can’t be the result of the Jezero impact itself, which occurred much later. Alex Jones, the paper’s lead author, explained: “Each layer records debris from a different impact event, some from far‑away collisions, some from nearby ones. Over time they piled up, creating this thick, sloping wall.”

There are hints, too, that water or ice might have played a role. On Earth, when molten rock meets ice, the rapid conversion to steam can trigger fast‑moving debris flows that solidify into layered deposits. The team speculates a similar process unfolded on early Mars, perhaps after a gigantic impact that formed the massive Isidis Basin (about 1,900 km across) and later the Jezero crater itself.

All of this helps scientists stitch together a timeline of planetary bombardment across the Solar System. By comparing impact records on Mars, the Moon, Mercury and Earth, researchers hope to refine models of how our planetary neighborhood evolved after the planets formed.

Perseverance continues its slow, methodical march along the rim, collecting samples that may one day return to Earth. For now, the ancient rock wall at Broom Point stands as a silent reminder that Mars has been keeping its oldest geological diary open – a diary that we are only just beginning to read.