Curiosity rover overcomes temporary freeze after 'attitude adjustment'

Last week, the rover didn't seem to understand where it was, so it essentially stopped its mission.

"Partway through its last set of activities, Curiosity lost its orientation," wrote Dawn Sumner, planetary geologist at the University of California Davis, in an entry for Curiosity's Mission Updates blog. "Some knowledge of its attitude was not quite right, so it couldn't make the essential safety evaluation. Thus, Curiosity stopped moving, freezing in place until its knowledge of its orientation can be recovered."

As Sumner explained in the blog post, rovers need to understand where their bodies are in relation to their surroundings, just like people. Curiosity's memory stores this body attitude, or position, so it knows the orientation of its various instruments and its arm. It also knows how those relate to its position on the ground or if any nearby hazards in its path. If it loses its attitude, the rover won't make any movement until it's fully aware.

During the freeze, Curiosity kept communicating with scientists on Earth so the team was able to understand what happened and come up with a plan to allow the rover's recovery.

NASA engineers created a plan that would allow Curiosity to regain its attitude, make safety checks and continue moving. The plan, transmitted to the rover, was successful and Curiosity was able to resume science operations again this week, according to another update from Scott Guzewich, atmospheric scientist at NASA's Goddard Space Flight Center.

Since the new year began, Curiosity has been exploring Mount Sharp's Western Butte to understand how the steep formation came to be. Although the butte is too steep for the rover to climb, the rover was able to sample and study some of the intriguing rocks that dropped down from the top of the butte to where the rover sat.

It also investigated a trough during its descent from the butte.

"In the images from orbit, it looks like someone drew a thick straight line with a dark felt marker on the southeastern side of the butte," wrote Melissa Rice, planetary geologist at Western Washington University in a mission blog post. "From the ground, it looks like a shallow ditch filled with dark sand. We don't know what created this feature, or why it happens to be right here, so it's worth stopping for a closer look."

Now that it's explored the butte and its surroundings, Curiosity will study bedrock targets; capture a mosaic of Western Butte; search for dust devils and study atmospheric dust; and measure the abundance of argon in the atmosphere.

"Approximately 25% of Mars' carbon dioxide-rich atmosphere condenses on the winter polar ice cap, while trace gases like argon do not," Guzewich wrote. "This leads to seasonal variations in the relative fraction of argon to carbon dioxide in the air. [Curiosity's Alpha Particle X-Ray Spectrometer] can measure this argon variation by simply turning on and looking at the sky while the arm is stowed. Seeing argon vary through the year is akin to watching Mars breathe!"