Mars and the Moon stage a spectacular encounter this evening. The Moon will slide just a fraction of a degree from the planet, which looks like a bright star.

Something we’ve learned about both of these worlds is that they have a lot of frozen water. On the Moon, it’s mixed in with the dirt and pebbles, or buried in craters that never see the Sun. On Mars, it’s also mixed in at the surface, but it’s also found in the polar ice caps, in layers of frost, and elsewhere.

On Mars, there’s even evidence of liquid water far below the surface. A study last year said there could be a lot of water buried in spaces in the rocks about 10 miles down – enough water to cover the surface of Mars in an ocean about a mile deep.

And earlier this year, scientists in Japan reported more evidence of that water. They analyzed the observations of the InSight lander, which operated for four years.

The craft listened for “marsquakes.” Sound waves from the quakes traveled through the planet. The new study looked at how different types of waves rippled through the interior. Each type of wave travels differently as it passes through different materials – rock versus water, for example. So comparing the waves revealed the likely presence of water miles below the surface. On Earth, where there’s water, there’s life. So an ocean’s-worth of water could provide a home for life on the Red Planet.

Script by Damond Benningfield