The rovers, which are working on the equator but on different sides of the planet, have been sending and receiving information from Earth most every day, with a team of about two-dozen programmers and engineers uploading code to guide the rovers' movements and aim their cameras. All of that information travels about 200 million miles one way, taking anywhere from five to 21 minutes to travel from one planet to the other.

"It is amazing. Every day I just have to tip my hat to the engineers who designed them," Banerdt said.

But all that time on Mars could be finally taking its toll on Spirit.

While Callas said they are in the early stages of an investigation into what is plaguing the rover, he did say that the robotic machine could be starting to suffer from age-related issues.

"In the past, when something has broken, we've been very innovative in finding a workaround," he added. "It could be that some memory cells were corrupted and we need to refresh them. It could be a transient thing, like when your computer crashes and you don't know why. It could be that it's getting older and it's getting more temperamental. We're obviously aware of the fact that we have an old rover here," Callas said.