Like most humans, astronomers tend to be pack rats. We collect all sorts of equipment and books and paper and data, and we are very slow to rid ourselves of it. But what should we hold onto, and when should we let go?
This question has been rolling around my mind for a few weeks (though off and on longer than that), starting with the announcement that one of the Mars rovers might have to be shut down, and the subsequent reversal of that decision. And the furor over the Mars funding may have led to one NASA leader resigning his post.
The problem NASA faced at Mars (and has to face with other space missions) is how to gracefully end missions that could be continued, though with ever dwindling science output. The Mars Rover Spirit is limping along, spending its Martian winter (about twice the length of Earth winters) parked on a steep slope to try and catch enough sunlight to keep from freezing. When it does move, it is dragging a wheel. Spirit's rock-grinding tool is worn down, and some of its other science instruments are not functional. But Spirit can still take pictures and do some science measurements, the public loves the rover, and it is easy to be emotionally invested in the rover, rooting for it to survive another year against the odds.
But the costs of operating a rover are high, tens of millions of dollars a year. And that money has to come from somewhere -- typically it is cut from future science missions. So, which is more valuable? A shrinking return from the famous and intrepid Spirit rover, or investment in future science missions? I think we are rapidly reaching a point with Spirit (if we haven't already) where the poor rover just can't give us enough worthwhile data. The decision is complicated by the ever-increasing number of NASA robotic missions, which are placing an ever-increasing demand on NASA's Deep Space Network of radio antennas that communicate with the space probes, and NASA's big (and costly!) plans for new manned rockets, new technology, and ambitious robotic missions (like a Mars sample-return mission, or a lander for Jupiter's moon Europa).
But it's not as simple as that. If the rover (or any mission) is threatened, the people working on the mission will fight. They've invested the better part of a decade or two in this robot, and they want to run it into the ground and not have to look for other jobs working on someone else's pet project. These are completely understandable and valid point, but, again, maybe not the most scientifically productive stance.
So, the people upset when their mission is about to be ended complain, and complain publicly. And then the public, which really loves the rovers or robots or space telescope, complain. We astronomers are grateful that people care enough about our work to complain about it to our government; this has helped rescue great science in the past, and it will in the future! It's also inspiring to know that we are doing work that people care about. But, again, is it worth lots of money to keep a program limping along? The court of public opinion may not be the right place for that battle to be fought.
Personally, I think that the members of science teams and members of the public will accept that all missions must end, and sometimes before the robot is completely dead. Some will accept such decisions only grudgingly. But there are better ways to make such announcements than short memos. A science mission as successful as the Mars rovers deserves better. I think missions like this deserve a wake, a celebration of the mission's life, the many people involved, the sweat and frustration they put into their work, and the great science that came out of it. That affirmation of the value of the mission and the people involved is the least we can give, and it lets a mission go out with a bang instead of fading into the cold, harsh reality that is outer space and federal budgets.
For now, though, the Mars rovers will continue to plod along, collecting useful data on the Red Planet, even as the next wave of Martian landers approaches to begin their own exciting research.