2 min read

Margin’ up the Crater Rim!

An image from the Martian surface shows light beige, rocky terrain under a sky that’s a cool, pale yellow and casts a haze across the scene. The camera’s-eye view from below the rover shows the robotic arm reaching for a large, flat rock just left of image center, and atop the rock is a circular indentation where it looks like a medium-sized coin was pressed into the dirt. A section of the rover blocks off the top quarter of the image frame, while a support rod stretches toward one of the rover’s wheels, at the right edge of the frame, where it’s viewed edge-on, so you can see the swirl of its spokes, and the ribbed tread of its wheel.

NASA's Mars rover Perseverance conducts proximity science on the Eremita Mesa abrasion patch in the Margin Unit on Sept. 6, 2024, as it continues its traverse up the rim of Jezero Crater. Perseverance acquired the image using its Front Left Hazard Avoidance Camera A (Hazcam) on sol 1261 — Martian day 1,261 of the Mars 2020 mission — at the local mean solar time of 13:53:53.

NASA/JPL-Caltech

To conclude its exploration of the mysterious margin unit before it ascends the rim of Jezero Crater, Perseverance made one last stop this past week to investigate these strange rocks at “Eremita Mesa.”

Since beginning its steep drive up the crater rim, Perseverance has been traversing along the edge of the margin unit (the margin of the margin!), an enigmatic unit rich in carbonates, a mineral group closely linked to habitability. Here, the rover team scouted out a mound of rock called “Specter Chasm,” where Perseverance cleared away the dusty, weathered surface with its trusty abrading bit. The resulting abraded patch, called Eremita Mesa, is pictured above being investigated by Perseverance’s proximity science instruments mounted on its robotic arm. This includes taking close-up images to examine the millimeter-scale particles that make up the rock, using the WATSON (Wide Angle Topographic Sensor for Operations and eNgineering) camera, which functions as Perseverance’s magnifying glass.

Before the rover began exploring, investigations using orbital satellite data had suggested the margin unit rocks may have formed in several different ways. Theories the team has been exploring include that the unit formed on the shoreline of the ancient lake that once filled Jezero Crater, or instead that it was produced by volcanic processes such as pyroclastic flows or ashfall, or ancient lavas flowing into the crater. Since Perseverance began its investigation of the unit in September 2023, more than 350 sols ago (1 sol = 1 Mars day), the Science Team has been scouring data collected by the rover’s instruments to help constrain the unit’s origin. So far, this has remained largely a mystery, with the original rock textures potentially heavily affected by alteration since it formed more than 3 billion years ago. Perseverance has already collected three exciting samples of this curious rock unit for future Earth return: “Pelican Point,” “Lefroy Bay,” and “Comet Geyser,” and the team is hoping the data collected at Eremita Mesa could help further constrain the ancient processes on Mars that formed these strange rocks.

Next, it’s onwards and upwards for Perseverance as it faces a steep climb up the crater rim, where perhaps even more exotic and exciting rocks await!

Written by Alex Jones, Ph.D. student at Imperial College London