For all the hopes NASA has pinned on the rover it deposited on Mars last month, one wish has gone unspoken: Please don't find water.
Scientists don't believe they will. They chose the cold, dry equatorial landing site in Mars' Gale Crater for its geology, not its prospects for harboring water or ice, which exist elsewhere on the planet.
But if by chance the rover Curiosity does find H2O, a controversy that has simmered at NASA for nearly a year will burst into the open. Curiosity's drill bits may be contaminated with Earth microbes. If they are, and if those bits touch water, the organisms could survive.
The possible contamination of the drill bits occurred six months before the rover's launch last Nov. 26. The bits had been sterilized inside a box to be opened only after Curiosity landed on Mars.