Moon and Mars

Gale Crater is dry, cold, and quiet. But the Martian feature hasn’t always been that way. More than three and a half billion years ago, for example, heavy rains produced massive flooding — perhaps leaving the crater warm and wet for centuries.

For the last eight years, the Curiosity rover has been crawling around the crater and on the flanks of the tall mountain at its center.

The rover has photographed rock formations in the crater. Some are mostly buried below the sand. They include giant “waves” — formations that are three stories tall and longer than a football field. They probably formed during heavy flooding.

Scientists who analyzed the rover’s findings outlined a possible scenario:

More than three and a half billion years ago, an asteroid slammed into Mars. It blasted frozen carbon dioxide and methane into the atmosphere. That warmed the entire planet. Clouds then dumped massive amounts of rain, which began filling Gale Crater and pouring down the sides of its mountain. That created torrents of water up to 75 feet deep, moving at more than 20 miles per hour.

The floods may have lasted just a few days. But the warm, wet conditions could have hung around for a lot longer — making Gale Crater one of the most interesting spots on Mars.

Look for Mars above the Moon this evening. It looks like an orange star. The true star Aldebaran — which is also orange — is about the same distance to the upper left of the Moon.

Script by Damond Benningfield