Curiosity Blog, Sols 4743-4749: Polygons in the Hollow
Written by Lucy Lim, planetary scientist at NASA’s Goddard Space Flight Center
Earthworks planning date: Friday December 12, 2025
The weekend trip from the “Nevado Sajama” drilling site brought Curiosity back into the hollow of the “Monte Grande” caisson. We have already been in this trough for the “Valle de la Luna” drilling campaign, but now that the team has seen the results from the “Valle de la Luna” and “Nevado Sajama” drilled samples, we have decided that there is still work to be done here.
Overall science objectives included analysis of the other well-exposed Monte Grande boulder to improve our statistics on bedrock composition in the troughs, as well as high-resolution imaging and compositional analysis of portions of the trough walls, other than those that had been covered during the Valle de la Luna campaign. These are part of a systematic mini-campaign to map a transect over the crested hollow structure from top to bottom at this site.
Post-drive imaging revealed a surprise: the neighboring block of Valle de la Luna was covered in polygons! It turned out that the position of the rover during our previous visit for the Valle de la Luna drilling campaign had hampered the imaging of the polygonal features of this block, so this was our first good look at them. We have seen broadly similar polygonal patterns before in various strata of Gale Crater – recently in the layered sulfate units (e.g., during Sols 4532-4533 and Sols 4370-4371), but we had not seen them at the bottom of a box-shaped trough. Interestingly, this block has a fluffier texture than most previously observed polygon-covered blocks.
We are interested in the relationship between the visibly protruding fracture fill material here and the fracture fill material observed in previous polygons, as well as the relationship between the top polygonal surface and the more chaotic-appearing exposures lower down the block, and to the equivalent strata in the nearby trough wall. We have therefore planned an oversized MAHLI mosaic which will support the three-dimensional modeling of the upper and lower exposed surfaces of the polygon supporting block. Several APXS and ChemCam LIBS observations targeted at the centers and crests of the polygons were also planned, to measure the composition. Meanwhile, Mastcam took care of planning stereo images of the neighboring hollow wall in addition to the individual blocks on the hollow floor.
The trough also included freshly exposed light-colored material from which the rover had rolled and scraped a bedrock. So another APXS measurement and a LIBS ChemCam went to the scratched area to measure the fresh surface.
We will drive onto Sol 4748. As we drive, we will conduct a “sidewalk” observation TUESDAY, to image the ground beneath the rover as we approach the wall for a closer view, and hopefully some contact science in next week’s plans.
