MELISSA BLOCK, host:
NASA's robotic chemistry lab on Mars has made a surprising finding. According to instruments on the Phoenix Lander, the soil near the Martian north pole contains measurable amounts of a substance called perchlorate. Perchlorate can be nasty stuff. Back on Earth, it's used for making rocket fuel.
NPR's Joe Palca explains what the discovery means to the possibility of finding life on Mars.
JOE PALCA: NASA sent Phoenix to the north polar region on Mars to see if the environment there might be hospitable to some kind of life. Mission scientist Samuel Kounaves of Tufts University says it's wrong to think of perchlorate as toxic.
Mr. SAMUEL KOUNAVES (Mission Scientist, Tufts University): I wouldn't use the word toxic. I mean, even table salt is toxic at high enough levels. It's actually positive in two ways.
PALCA: Kounaves says perchlorate contains a lot of energy. Some organisms on Earth even thrive on it.
Mr. KOUNAVES: There are several bacteria that utilize perchlorate, and there are several plants - quite a few plants - that actually grow on perchlorate, and some of them even concentrate it.
PALCA: The other way it's positive is perchlorate contains a lot of oxygen. That oxygen is what makes stuff like rocket fuel burn. But Kounaves says it could also provide oxygen for visitors from Earth to breathe. There are still questions about the perchlorate measurement. Another instrument on Phoenix that could detect perchlorate hasn't - at least not yet. And scientists want to be certain that the perchlorate didn't come from the rocket fuel that propelled Phoenix to Mars.
Kounaves says NASA wanted scientists to tie up some of those loose ends before announcing the perchlorate finding. But when news of the finding began to trickle out, NASA decided it couldn't wait.
Mr. KOUNAVES: Unfortunately, out there on the blog world and the dotcom world, a lot of rumors started creeping around, and they were mostly inaccurate rumors.
PALCA: So NASA decided to set the record straight. Joe Palca, NPR News, Washington.
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