Perseverance spent this week on Mars roving across the top of the Jezero fan- from Mount Meeker to Dream Lake- in search of yet another sample for return to Earth. This upper region known as Lobe K is expected to contain some of the most recently deposited materials within the delta sequence, providing the opportunity to place both upper and lower bounds on the timing of aqueous activity that built the fan. Another interesting feature of this region includes an array of boulders that dot this region. These rocks are compelling because they are thought to have been sourced outside the watershed, transported from afar by the water that flowed into Jezero crater long ago. After sampling in-place material from Lobe K, the team plans to collect a core from one of these boulders. With this target, scientists hope to gain insight into both local and distal geologic history, including the geochemical conditions where the boulder formed, depositional processes that brought this material to Jezero, and environmental changes that have occurred since emplacement. Since these large rocks are thought to have been transported to the region after the fan formed and set down on top of the Lobe K material, this sample will help scientists better understand how Jezero and the Martian environment continued to evolve throughout time. Boulders are also great rocks for performing geochronological analyses!
There may be an abundance of compelling targets in Lobe K, but collecting a sample from this lithology has presented a challenge. The last core Perseverance drilled was a conglomerate called Otis Peak at the Onahu outcrop, and the soft and crumbly nature of this outcrop meant that several attempts were required before the team was able to successfully collect a core. Now it’s a different story- these rocks are much harder. Perseverance initially performed abrasion and proximity science on a target called Dragon’s Egg in preparation to sample the adjacent Lost Lake, but the rock was so hard that the abrasion bit was only able to partially grind into the target, and the drilling bit was unable to dig deep enough to collect a core with the required 2.5 cm length. The team decided to leave the workspace- with a trove of data from the Dragon’s Egg abrasion prox sci in hand- and head to Dream Lake to look for another Lobe K rock to sample. These rocks may be tough, but Perseverance is tougher and won’t give up until the core is secured!