About 3.5 billion years ago — around the time life is thought to have first arisen on Earth — Mars had a large freshwater lake that might well have been hospitable to life, scientists reported Monday.
The lake lay in the same crater where NASA’s Mars rover Curiosity landed last year and has been exploring ever since. It lasted for hundreds or thousands of years, and possibly much longer.
Whether any life ever appeared on Mars is not yet known, and Curiosity was not designed to answer that question. But the data coming back from the planet indicate that the possibility of life, at least in the ancient past, is at least plausible.
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