Curiosity Blog, Sols 4750-4762: See You on the Other Side of the Sun

Written by Lucy Thompson, planetary scientist and APXS team member, University of New Brunswick, Canada

Earth Planning Date: Monday, December 22, 2025

As we all prepare for the holiday season here on Earth, we're planning a few last activities before Curiosity and its team of scientists and engineers take a well-deserved long break. This holiday season coincides with the conjunction: every two years, due to different orbits, Earth and Mars are blocked from each other by the Sun; this one will run from December 27th to January 20th. We don't like to send commands through the Sun in case they get confused, so we're finishing up a few last science observations before preparing Curiosity to quietly disconnect.

As part of a pre-planned cross-section between two of our recent drill holes, Valle de la Luna (trough) and Nevado Sajama (ridge), we successfully completed chemical analysis and imaging of the ridge wall. These observations were obtained to document changes in texture, structure, and composition between the two wells, and to understand why we see such contrasting physical characteristics of stable ridges and eroded basins in this region. Mastcam and ChemCam also captured images a little further away. ChemCam continued its observations of the Mishe Mokva hill and recorded textures on the northern wall of the next adjacent depression. Mastcam photographed the central fracture along the Altiplano ridge above the wall we parked against, as well as the polygonal features in our previous workspace.

Rover engineers then successfully orchestrated Curiosity's return trip to a nearby ridge to provide a safe place to park during the connection. We documented the ride with MARDI video from the sidewalk, tracking how the terrain underneath the rover changed as it drove. While we haven't been able to use APXS and MAHLI on the robotic arm since Friday due to restrictions that must be set before conjunction, we have been able to use the rover's Mastcam to image regions of interest in the near field, which will help guide our planned actions when we return from conjunction. We hope these will include obtaining chemical data (using APXS and ChemCam) and imaging (using MAHLI) of some of the freshly eroded rock surfaces we drove over.

Environmental scientists were also very busy. Navcam observations included: Navcam videos of the superhorizon and zenith for cloud observations; Line-of-sight observations using Navcam; and Navcam images and reviews of dust devils as we enter dust storm season on Mars. Mastcam tau observations were conducted to monitor atmospheric optical depth, and APXS atmospheric analysis was also planned to monitor seasonal changes in argon.

Today we are broadcasting the last plan before Mars disappears behind the Sun and we all take a break (the actual conjunction plan that will take us through sols 4763-4787 was connected a couple of weeks ago). Due to restrictions put in place to ensure the safety and health of Curiosity, we have limited ourselves to a very small number of activities today. These include additional APXS measurements of atmospheric argon, as well as Hazcam and Navcam imaging, including monitoring of dust devil activity.

As usual, our plans also included background observations of DAN, RAD and REMS, which continue until conjunction.

It was a pleasure to be part of this great team for another year. We're all looking forward to returning in January when Mars reappears from behind the Sun for another exciting year of exploring Gale Crater.