Mars rover works its way out of crater

[David Brinza]

Graphite isn't a good lubricant in vacuum. Absorbed water vapor and gas between the planes of carbon atoms in graphite makes it "slippery". Molybdenum disulphide (Moly-lube) is a much better dry lubricant in vacuum.

There are special greases that won't outgas or creep out of the mechanism. Finding non-contaminating lubricants that will work well at -100 degC (or colder) was a problem.

The specific lubricants that are used in the rovers probably cannot be disclosed publicly, due to export control (ITAR)* restrictions.

* Even though the rovers are not military in nature, the US State Dept considers space systems technical data to be sensitive information that cannot be disclosed to non-US persons without specific permission. (This is probably a topic for an entirely different thread).