NASA's Curiosity rover isn't done finding signs that Mars once had the prime ingredients for life... not by a longshot. The explorer robot has discovered evidence of nitrates, the nitrogen compounds that are some of the key nutrients for life, in rocks at three places near its landing site. This still doesn't mean that Mars did harbor life in its heyday, but it's now that much more likely. The big question is whether the processes that formed those nitrates are still active, or if they died out when the planet became barren -- scientists aren't sure, and it could take a while to get an answer.
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