The average depth of the oceans on Earth is a little more than two miles. And the greatest depth is about seven miles. But that’s little more than a big puddle compared to the ocean on Ganymede, the biggest moon in the solar system. Its ocean appears to be about 60 miles deep. And it covers the entire moon. That means that Ganymede’s ocean probably contains several times as much water as all of Earth’s oceans combined.

Ganymede is the largest moon of Jupiter, the largest planet. It’s almost 3300 miles in diameter — bigger than the planet Mercury. It’s more than twice as far from Jupiter as the Moon is from Earth. Its crust is about a hundred miles thick, and is made of frozen water. The ocean is below that cap.

Scientists are pondering whether the ocean could be a good habitat for life. There’s another layer of ice below it. But if the ocean comes in contact with rocks, then geysers of hot water with lots of minerals could spew into the water. That would provide the energy and chemistry for life.

Observations by the Juno spacecraft suggest there could be such contact. Juno found salts on the surface of Ganymede. It might also have seen organics — the chemical building blocks of life. So water could have “leaked” to the surface — providing intriguing evidence of conditions in Ganymede’s deep ocean.

Jupiter is close to our moon tonight. The planet looks like a brilliant star above the Moon.

Script by Damond Benningfield