SarahAskew

Mercury's unseen hemisphere, imaged by MESSENGER on its first flyby in January 2008. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

The NASA MESSENGER (MErcury Surface, Space ENvironment, GEochemistry and Ranging) probe swung by Mercury for the second time in the early hours of today. The smallest planet in the solar system since Pluto’s downgrading, Mercury has always been a bit of a mystery to scientists.

What we do know is that it’s a pretty hostile place with big extremes of temperature because of its proximity to the Sun. Also, the planet’s gravitational pull is too small to hold on to anything but the thinnest of atmsophere.

NASA’s MESSENGER probe is the first space mission to visit Mercury since Mariner 10 in the mid-1970s. Until its arrival at Mercury and the first flyby that took place in January of this year, an entire hemisphere of the planet had never been imaged. So we’re all very excited about seeing the pictures from MESSENGER. I’ll post them here when they’re released!