AILSA CHANG, HOST:
Later tonight at Europe's spaceport in French Guiana, a probe is scheduled to lift off. Its goal, as NPR's Joe Palca reports, is to explore the mysteries of Mercury.
JOE PALCA, BYLINE: Mercury is a funny little planet. Like the Earth, it has a metal core. But Mercury's metal core takes up most of the planet.
NANCY CHABOT: You can imagine it as a giant metal ball surrounded, like, a little bit of rock on the top.
PALCA: Nancy Chabot is a planetary scientist at the Johns Hopkins Applied Physics Laboratory. She worked on a NASA probe called Messenger that orbited the innermost planet to the sun earlier this decade. Messenger proved Mercury holds some surprises. Despite 800-degree temperatures on the sunny parts of the planet, there are places in craters near the poles that never see the sun.
CHABOT: In these permanently shadowed regions, it is cold enough that water ice is stable for billions of years.
PALCA: Yes, ice. Messenger only got close enough to see ice at the north pole. But Chabot says the real icy action is at the south pole.
CHABOT: The largest crater to host these water ice deposits is right smack-dab at the south pole of Mercury. And so I'm very excited that BepiColombo is going to be in an orbit that passes much closer to the southern hemisphere.
PALCA: Bepi Colombo was an Italian scientist after whom the European Space Agency mission is named. It's actually two probes, one that will orbit the planet close up and another supplied by the Japanese space agency that will be further out, measuring Mercury's magnetic field. There's one feature on Mercury Chabot is particularly curious about.
CHABOT: The crater made by Messenger.
PALCA: At the end of its mission, Messenger managers decided to crash the spacecraft into the planet.
CHABOT: Once BepiColombo gets into orbit, they should be able to take the highest resolution image they possibly can. And we might be able to see Messenger's final resting spot.
PALCA: It's more than sentiment that makes Chabot curious about the crash site. The impact will undoubtedly have tossed up lots of debris.
CHABOT: And we might be able to learn something about that freshly exposed material and more about Mercury.
PALCA: BepiColombo will take seven years to reach Mercury. It flies once by Earth, twice by Venus and six times by Mercury before it's in the right orientation to go into orbit around the hot little planet. Joe Palca, NPR News.