PASADENA—NASA’s Perseverance rover has found evidence that a thick, ancient rock sequence at the rim of Jezero Crater was assembled by repeated asteroid impacts rather than by slow, steady deposition. The stack—about 245 feet (75 meters) of layered bedrock—was dubbed the “Broom Point member” by the science team, and appears to predate the crater-forming event. If the interpretation holds, the deposit is likely older than 3.9 billion years, placing it among the most ancient terrain ever investigated by a Mars rover.
In early 2025, Perseverance surveyed the western rim of Jezero and used its instruments to identify six distinct rock types within the Broom Point sequence. Several layers include breccias—rocks composed of angular fragments—intermixed with intervals of fine-grained, pulverized dust. Within the breccias, rock fragments contain tiny cavities left behind by gas bubbles, a signature that the fragments were once molten during formation.
A striking clue comes from dark, glassy beads embedded in the layers. Such droplets can be produced by volcanic activity, but their unusually high abundance suggests an impact-driven origin. The study notes that the largest beads are comparable in scale to those thrown during Earth’s Chicxulub asteroid impact that helped end the age of dinosaurs.
Because the same rock varieties recur multiple times through the sequence, the team argues that high-energy impacts struck repeatedly across the region of early Mars. The mixture of “large-impact” and “small-impact” layers implies varying distances between each impact source and the area where the ejecta ultimately accumulated.
The deposits may also reflect transient water or ice. Some layers resemble debris-flow deposits that could have formed when hot material blasted into water or ice, rapidly flashing it to steam—an Earth-like mechanism that creates fast, ground-hugging surges.
The architecture is even more dramatic: several layers tilt at angles exceeding 80 degrees, nearly vertical. That geometry cannot be explained by the single impact that created Jezero Crater, meaning the rocks were already disturbed before Jezero formed.
Scientists propose a two-stage cosmic event. First, a massive impact created the Isidis Basin, toppling and tilting earlier rocks. Later, Jezero Crater formed, fracturing and uplifting the already inclined layers into the steep, rugged structure Perseverance now traverses.
To anchor the timeline, Perseverance collected two core samples from the region, named “Bell Island” and “Main River.” If future missions return them to Earth, radiometric dating could establish when the impact barrage occurred and help reconstruct how early Mars—and possibly early Earth—was hammered during the solar system’s formative violence.
Subject of Research: Jezero Crater rim stratigraphy (Broom Point member) formed by repeated asteroid impacts
Article Title: Stratigraphy Preserved on the Jezero Crater Rim Reveals Repeated Impacts on Early Mars
News Publication Date: 15-Jul-2026
Web References: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2026JE009779
References: doi:10.1029/2026JE009779
Image Credits: Not provided in the content
Keywords
Mars; Perseverance; Jezero Crater; early Mars; asteroid impacts; breccia; glassy beads; stratigraphy; Isidis Basin; sample return chronology
