Jezero Crater, which is twenty-eight miles (45 kilometers) wide, is an ancient fan-shaped feature that formed about 3.5 billion years ago at the convergence of a Martian river and lake. Thomas Zurbuchen, NASA’s deputy administrator for science in Washington, said: “We chose Jezero for Perseverance Crater to explore because we thought it had the best chance of providing scientifically excellent samples – and now we know we sent the rover to the right location. “ “These first two science missions have yielded an amazing variety of samples that will be brought back to Earth by the Mars Sample Return campaign.” Perseverance project scientist Ken Farley of Caltech in Pasadena, California, said: “The delta, with its varied sedimentary rocks, contrasts beautifully with the igneous rocks – formed by the crystallization of magma – discovered on its floor crater. This juxtaposition provides a rich understanding of the post-crater geologic history and a variety of samples. For example, we found a sandstone with grains and rock fragments created far from the Jezero crater and a mudstone with interesting organic compounds.’ The rock was named Wildcat Ridge, which formed billions of years ago as mud and fine sand settled in an evaporating saltwater lake. The Perseverance rover on July 20 skimmed some of the surfaces of Wildcat Ridge so it could analyze the area with the SHERLOC instrument. SHERLOC analysis shows that the samples possess a class of organic molecules spatially correlated with those of the sulfate minerals. Sulfide minerals found in sedimentary rock layers can provide important information about the aquatic environments in which they formed. Farley said, “In the distant past, the sands, silts, and salts that now make up the Wildcat Ridge sample were deposited under conditions where life could have thrived. The fact that organic matter was found in such sedimentary rock – known for preserving fossils of ancient life here on Earth – is significant. However, as capable as our instruments on Perseverance are, further conclusions about what is contained in the Wildcat Ridge sample will have to wait until it returns to Earth for in-depth study as part of the agency’s Mars Sample Return campaign.” The geological diversity of the samples already brought to the rover is so good that the rover team is considering depositing selected pipes near the base of the delta in about two months. After depositing the cache, the rover will continue its delta explorations.
