NASA this afternoon released the first-ever photo of Mercury taken from a spacecraft in orbit around the innermost planet of the solar system.
The most arresting element of the photo is the rayed crater Debussy, which lends to the overall image the impression of the vine end of a cantaloupe after the vine has been snapped off. Straight out to the left of Debussy and much smaller, about halfway to the left border, lies the crater Matabei "with its unusual dark rays," NASA says.
The space agency has seen Debussy and Matabei before. What it hasn't ever seen until now is a region of Mercury that lies in the darker bottom half of the image, in the direction of the planet's south pole.
The photo comes from the Messenger spacecraft, which took off from Earth in 2004 and which has taken plenty of flyby photos of Mercury since 2008. Earlier this month, Messenger became the first spacecraft to go into orbit around Mercury. And with that, scientists are hoping to get a much fuller sense of the inhospitable planet, addressing questions such as these: Why is Mercury, the planet closest to the sun, so dense? How big is the planet's core, and is the outer core really molten? What are the unusual materials at its poles--could that actually be ice?
In the six hours after snapping this image of Debussy and environs at 2:20 a.m. PT today with the Wide Angle Camera of the Mercury Dual Imaging System, Messenger acquired 363 more images and began downloading the data to researchers here at home. NASA plans to release additional images tomorrow.
The spacecraft is still in what NASA refers to as the commissioning phase of its mission, as Messenger and its instruments get checked out. The science mission begins April 4 and is expected to last at least a year and to generate more than 75,000 images.
Messenger, by the way, stands for MErcury Surface, Space ENvironment, GEochemistry, and Ranging.
Update March 30 at 12:48 p.m. PT: NASA has released a small sample of other initial orbital photos at the Messenger site maintained in conjunction with the Johns Hopkins University Applied Physics Laboratory, including an annotated guide to the first orbital image, a first look at terrain near Mercury's north pole, and the first color image (the colors are very subtle) of Mercury from orbit.