This illustration shows NASA's Cassini spacecraft diving through the plume of Saturn's moon Enceladus, in 2015. Two veteran NASA missions are providing new details about icy, ocean-bearing moons of Jupiter and Saturn, further heightening the scientific interest of these and other "ocean worlds" in our solar system and beyond. via NASA

NASA scientists are releasing new global maps of Earth at night, providing the clearest yet composite view of the patterns of human settlement across our planet. This composite image, one of three new full-hemisphere views, provides a view of the Americas at night. via NASA

Through NASA's Space Technology Research Fellowship (NSTRF) program, a fresh approach to designing and manufacturing heat-thwarting thermal protection systems - or heatshields - for spacecraft is being developed and tested, offering the promise of fabricating larger tile sizes while reducing labor, cost and waste. via NASA

A horse drawn caisson carries former astronaut and U.S. Senator John Glenn to his final resting place during the interment ceremony at Arlington National Cemetery on Thursday, April 6, 2017, in Virginia. Glenn was the first American to orbit Earth on Feb. 20, 1962, in a five-hour flight aboard the Friendship 7 spacecraft. via NASA

This illustration shows NASA's Cassini spacecraft about to make one of its dives between Saturn and its innermost rings as part of the mission's grand finale. Cassini will make 22 orbits that swoop between the rings and the planet before ending its mission on Sept. 15, 2017, with a final plunge into Saturn. via NASA

Expedition 50 Flight Engineer Thomas Pesquet of the European Space Agency (ESA) photographed brightly glowing auroras from his vantage point aboard the International Space Station on March 27, 2017. Pesquet wrote, "The view at night recently has been simply magnificent: few clouds, intense auroras. I can’t look away from the windows." via NASA