A shallow puddle in the Wright Valley, 9 km west of Lake Vanda, that is 30 percent saltier than the Dead Sea and does not freeze at minus 50. The salt is not the sodium chloride you would expect but calcium chloride, leached out of the dolerite bedrock and concentrated by evaporation until the freezing point of the water dropped clean off the bottom of the Antarctic temperature range. That is why planetary scientists keep coming back to a pond you could wade across: it is the closest thing on Earth to how liquid water could persist on Mars, and the recurring slope streaks on Martian hillsides are argued about in these terms. Victoria Land, East Antarctica.
Wright Valley, Antarctica
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