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Continuing in the tradition started by the Cassini mission to Saturn, Scientist for a Day challenges students in grades 5-12 to think like NASA scientists. Examine real spacecraft images of Saturn’s moon Enceladus, Saturn’s moon Titan, and Jupiter’s moon Europa. Choose the destination you think would be the best place to return with another spacecraft to learn even more about these amazing worlds. Support your choice in an essay of no more than 500 words. Which of these three moons inspires you to explore further? What excites you about what we’ve learned so far? What do you hope we’ll find if we return to these places? If you like, you can even tell us which science instruments you would put on the next spacecraft to help us learn even more.

The 2018-19 essay contest is sponsored by the Radioisotope Power Systems program. This is the group at NASA that develops the power technology that enables spacecraft to explore the planets and moons of the outer solar system. For more information about Radioisotope Power Systems, visit

2018-2019 Topics

Topic 1


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

Topic 2


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

Topic 3


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