Jezero Crater Contains Aqueously Altered Igneous Rocks

The Perseverance rover took this selfie next to a recently drilled rock. Credit: NASA/JPL-Caltech/MSSS.

The Perseverance rover touched down in the Jezero Crater on Mars on February 18, 2021. The rover had three main science objectives: to collect rock core samples that would eventually be returned to Earth, to explore the geology of the crater in which it landed, and to identify potentially habitable ancient environments and evaluate the possibility of inhabitation. The 45-kilometer-diameter crater was selected because of evidence that the crater once contained an open lake system with a large delta. On Earth, this kind of environment is full of life, so this ancient delta system would be an ideal location to look for signs of ancient life. However, as Perseverance started analyzing rock samples, results showed that the area was not as wet as once thought.

The Perseverance rover analyzed four rock locations along a 2.4-kilometer traverse using multiple cameras, a ground penetrating radar, various spectrometers, and microscopic cameras. Kenneth Farley from the California Institute of Technology and his team unraveled the geologic story of the rocks in that area, including their composition, formation, and aqueous history. Jezero Crater consists of two geologic units: the Máaz, which is an igneous unit that cooled slowly, and the Séítah, a unit composed of olivine, magnesium oxides, and magnesium sulfates. Both units have bright white patches of various salts, including perchlorates and sulfates. The rocks show evidence of alteration by water, but their textures, mineralogy, and compositions were not destroyed. Signs of alteration include carbonates and iron oxides, deposition of salts, in-situ carbonation of olivine, and possible production of serpentine from pyroxene or olivine. However, there is no evidence of extensive interaction with a large volume of water. Both the Máaz and Séítah formations appear to be composed of nearly pristine igneous rocks, suggesting that there was less water in Jezero Crater than previously thought. READ MORE