Washington Post: NASA's Curiosity rover found evidence of an ancient lake on Mars.
Scientists have known that the young Mars was more Earthlike than the desert planet we see today, but this is the best evidence yet that Mars had swimming holes that stuck around for thousands or perhaps millions of years. (It would have been very chilly — bring a wet suit.)
Scientists had announced this year that they’d found signs of an ancient, fresh-water lake within Gale Crater, but the new reports provide a much more detailed analysis, including the first scientific measurements of the age of rocks on another planet. The research suggests that Martian winds are sand-blasting rock outcroppings and creating inviting places to dig into rocks that may retain the kind of organic molecules associated with ancient microbes.