Learn why NASA scientists are so excited about all three of this year’s essay contest topics. All three of these moons are interesting to astrobiologists, because they all contain liquid water oceans underneath their icy surfaces. On Earth, wherever we find water, we find life. Could this be true on other worlds, too?

Topic 1: Enceladus

This moon of Saturn has active ice geyers at its south pole that are feeding one of Saturn’s rings.

Enceladus, the sixth largest moon of Saturn, has active ice geysers at its south pole. The Cassini spacecraft flew through the plumes from these geysers in 2015.

Topic 2: Titan

This moon of Saturn has a dense atmosphere, mountains made of ice, and lakes made of methane.

Titan, the largest moon of Saturn, has a nitrogen and methane atmosphere that is more dense than Earth’s atmosphere. The liquid lakes on its surface are made of methane and ethane. The Cassini spacecraft used radar to peer through the atmosphere to map Titan’s surface from 2004-2017.

Topic 3: Europa

This moon of Jupiter has more water under its icy crust than all of the water in Earth’s oceans.

First seen by the Italian astronomer Galileo Galilei in 1610, this moon of Jupiter has more water under its icy crust than all of the oceans on Earth. The cracks on its surface hint at activity below.

Could any of these worlds be habitable? If you could help NASA return to one of these moons with a robotic spacecraft, which moon would you choose to visit, and what do you hope we might learn there?

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