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Moon and Mars

July 13, 2016

We still have more than two long, hot months of summer here in the northern hemisphere. But the northern hemisphere of Mars is already headed into the cooler days of autumn, because the autumnal equinox was last week.

For parts of the southwestern United States, summer is monsoon season — the wettest time of year. Summer is the wettest time of year on Mars as well, but the dampness doesn’t come from rainfall. Instead, it comes from below ground.

At some latitudes, underground ice melts during summer, then squirts out onto the surface. Some of the liquid water trickles down slopes, forming dark streaks or small gullies.

And some recent research says that these trickles of water may alter the surface in more significant ways. In the vanishingly thin Martian atmosphere, the water quickly boils away. The boiling process may create turbulent streams that churn up grains of Martian sand like kernels of popcorn jumping around inside a popper. That kinetic flow can then trigger avalanches that rumble down hills and craters. So a small streamer of water may change the Martian surface in big ways.

And Mars is putting in a big showing over the next couple of nights. The planet looks like a bright orange star, and stands to the lower left of the Moon tonight. It’ll be even closer to the Moon tomorrow night. And a couple of other bright lights are near by: the golden planet Saturn and the orange star Antares.

We’ll have more about this lineup tomorrow.

Script by Damond Benningfield

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