get back from Mars?
The Mars Exploration Rovers will remain on Mars once the mission is over, just like the Sojourner rover, which operated on Mars in 1997 and it still there. It is very tricky to take off again from the surface of Mars once you are there, because there is no fuel there, so you would have to use whatever you brought with you. If you brought enough fuel to blast off again once you were at Mars, then the weight of that fuel makes the launch that got you there in the first place even harder (you need even more fuel to launch the extra fuel…you see where this is going?). There has not yet been a sample return mission to Mars for this reason, but in the next decade we will probably see our first successful sample return mission to Mars and back.
