EVA Report – December 21st

EVA # 10
Author: Hunter Vannier
Purpose of EVA: Investigate geologic units between Compass Rock and Somerville Overlook along/near Galileo Road
Start time: 1000
End time: 1456
Narrative: EVA began at 1100 led by Hunter and Cesare, joined by Jilian and Ryan. Opportunity started with 100% charge and 151.0 hours, and Perseverance started with 100% charge and 280.6 hours. The crew took Opportunity and Perseverance rovers north on Cow Dung Road and exited for Galileo road. They turned left at Compass Rock and continued along Galileo Road ~3/4 km before parking. The crew unloaded sampling tools and walked northeast along the road, taking in the beautiful views of the western portion of MDRS and Mancos shales, and Henry Mountains to the south where snow looked to be falling. As the crew walked, the Sun broke through the low, thin cloud cover and bathed the southeast faces of Factory Butte and accompanying edifices in light. The crew walked mostly in tan/pink/orange sand with dry vegetation on either side of the road and frequent animal droppings. ~1/2 km into the walk, the crew reached a large outcrop of fine-grained, orange/grey cross bedded sandstone overlain by darker sandstone and conglomerate lenses; at least one was a Morrison Formation member. This location was identified for sampling on the return to the rovers. The crew continued along Galileo Road and stopped to observe a stream bed (finding their beach), and continued uninterrupted until reaching Somerville Overlook, where they spooked some pronghorns. There were approximately 9 of them, and one had a glowing red nose which the crew didn’t second guess given the season. At the Overlook, we established a station on a small hill covered in a thin layer of grey, silt-sized regolith like material. Many red, orange, and purple opaque and crystalline material an average of 5 cm length (longest axis), probably chert and other chalcedony were common on the surface. Just below the surface, there was abundant bright white well consolidated material expected to be a layer of gypsum which was sampled. This layer was situated below light-toned sandstone exposed upslope and above the brown Triassic deposits that lay before the crew in the valley below. The crew took some photos and made their way back to the previously noted outcrop and obtained samples from boulders of the conglomerate lens and lower sandstone unit. As with almost all areas in MDRS where the Morrison formation is exposed, there were large 2-4 m boulders typically dominated by conglomerate lenses, though some interesting light/dark weathering rind striping was present at this location. The crew observed the largest pebbles in a boulder thus far on our mission, and also saw that often the desert varnish on smaller boulders welded a layer of conglomerate pebbles to the top of finer-grained sandstone. This made the boulder appear conglomerate dominated, when in reality was mostly composed of light-toned sandstone. After bagging samples, the crew returned to the rovers at 1305 and drove directly back to the HAB. The team made it back with Opportunity at 44% charge and 151.7 hours and Perseverance at 31% and 281.3 hours. They began the reentry process for the HAB at 1335.

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