In today's Science, the team behind the Phoenix Lander mission published four studies giving an assessment of their data since the lander died on the Martin surface last November. The odds look pretty good that liquid water once flowed on Mars.
The ice sheet Phoenix found just below the surface appears to have been liquid before it froze, and the surface is covered in calcium carbonate, a mineral that needs liquid water to form. Oh, and it snows at night.
The news comes on the heels of two studies of a water vapor plume emanating from Saturn's moon, Enceladus. After the Cassini spacecraft captured images of huge plumes of water vapor blasting from the surface of the moon, scientists got excited that Enceladus could in fact be home to a giant underground ocean of liquid water.
But the studies couldn't sort it out. The first used the Cassini spacecraft to identify salt in the plume's ice grains. The chemistry in the plume appeared to match what the scientists predicted for the theoretical ocean.
However, the second study looked at the vapor itself, rather than the ice grains in the vapor, and found practically no traces of sodium, dampening the enthusiasm.
Although the two studies would seem to be contradictory, they are not. It's possible that the vapor is fed by a freshwater supply, or that it evaporates too far down for the salt to be carried into the vapor. Or, perhaps, there is the correct amount of sodium in the vapor, but it's so small you can't detect it correctly from Earth.
Either way, something's going on in orbit around Saturn. Another of the planet's moons, Titan, has attracted flocks of astronomers to study its Earth-like geography. There may not be life on Titan, Mars or Enceladus but these worlds continue to tease us with the possibility.