Sojourner was a NASA rover that explored Mars in the late 20th century with the task of analyzing the composition of the Martian rocks and atmosphere.
The rover landed in 1997, and the location was named the Carl Sagan Memorial Station; by 2155, a monument stood in the location and was classed as a Mars Heritage Site. (ENT: "Demons")
During its mission, Sojourner approached a rock known as "Yogi". (Star Trek: Enterprise, opening credits)
Footage of Sojourner on Mars is featured in the opening credits of Star Trek: Enterprise. It has been claimed that this was the first instance of footage from another planet making it into a tv series or film. [1]
In the final draft script of "Terra Prime", the fact that the Sojourner was from the opening credits was noted and the vehicle, as depicted in the events of the episode, was said to look "dusty and motionless among familiar red rocks."