Author: Margaret Dean, Ph.D. Purdue University student
NASA's Mars 2020 rover is currently heading towards exciting new terrain. After about four months of climbing the rim of Jezero Crater, the rover takes a delightful ride across the plains just beyond the crater's western rim, aptly named Lac des Charmes. This area just beyond the Jezero rim will be the best place to look for ancient pre-Jezero bedrock and impactites – rocks formed or impacted by the impact event that created Jezero Crater.
The formation of a crater as complex as Jezero is, well… complex. Scientists who study impact craters like to divide the formation process into three stages: contact and compression (when the impactor hits), excavation (when materials are ejected from the crater) and modification (when gravity causes everything to collapse). This process occurs incredibly quickly, eroding the impact rock and even melting some of the target material. Sometimes on Earth, a classic “bowl” shaped crater has completely weathered and become unrecognizable, so geologists can identify craters by the remains of their impactites. Just when you thought it couldn't get any more difficult, the rim of Jezero Crater is located on the edge of another, even more pool called Isidis. This means that it is possible to discover impactites resulting from the formation of craters both in and around it, some of which may be several billion years old! We may have already encountered one of these blocks on our way to Lac des Charmes. In the foreground of this image taken by the rover's Mastcam-Z instrument is a potential impactite called a “megablock,” which the team dubbed “Hayha.” We can actually see this block from orbit, it's that big! The team looks forward to continuing to explore these ancient rocks as we take our next steps away from the edge of Jezero.
