Hubble.
NASA will no longer maintain the Hubble Space Telescope, saying that after the Columbia Shuttle explosion it is no longer safe to send shuttle maintenance missions to the beloved telescope. Of course, many people feel that this is actually because of the cost that will be incurred to sending humans to Mars--a project that has an even greater potential to be dangerous, and far less potential to as efficiently produce beautiful science. I remember after the Columbia explosion when pundits were sniping that they produce no good science I was aghast that they had forgotten Hubble. I don't think any single big science project, at least not in physics and astronomy, has engaged and enthralled as many people in my lifetime. A quote from Dr. James Beckwith, the director of the Space Telescope Institute at Johns Hopkins University, at the end of the NYT artice:

"We at the institute are devastated by the potential loss of Hubble. But we will do our absolute best to make the final years of its life the most glorious science you've ever seen.'"