15 December 2009

Smile for the Camera, Mercury

Posted by Michael McFadden

NASA/JHU-APL/CIWI’ve always thought that Mercury has gotten a bad rap. It isn’t pretty like Neptune, large like Jupiter or saddled with a funny moniker like Uranus. Only Pluto is so slighted but that guy isn’t even a planet anymore. In March 2011, however, NASA’s MESSENGER (Mercury Surface Space Environment, Geochemistry and Ranging) spacecraft will enter into orbit around our tiny, gray friend, giving it a well-deserved fifteen minutes of fame.

This afternoon in the session P23D MESSENGER’s Third Flyby of Mercury, we got a sneak peak into what we can expect in 2011. MESSENGER made its third flyby of Mercury at the end of November, the last push in a complicated loop-dee-loop that will make it the first spacecraft to orbit the planet.

The data MESSENGER sent streaming back to Earth during its three flybys confirmed what many scientists already expected: Mercury is quite the busybody. No wonder the Sun likes to keep such an eye on it.

Like Earth, Mercury has a magnetic field with two poles, which scientists believe originates from the planet’s fluid outer core, said Sean Solomon of the Carnegie Institution of Washington. Tumult between this field and solar winds creates a volatile system called a magnetosphere. Mercury’s magnetosphere is particularly dynamic, he said, shifting this way and that as it gets knocked about by the Sun.

Mercury’s tells a story of a violent past. It’s surface is pock-marked with volcanic scars, which may have played a large role in the planet’s formation, Solomon said. During its most recent flyby, MESSENGER snapped a photo of a particularly bright spot on the surface (see above). This spot could flag the planet’s youngest volcanic deposit.

The spacecraft also spotted more “lobate scarps,” bulging lines that criss-cross Mercury’s bleak landscape, according to Solomon. These lines may be the residue of tectonic activity–as Mercury cooled after its early years, its surface tightened like crumpled tin foil.

We’ve now seen about 98% of Mercury’s surface, Solomon said. The planet should get used to the paparazzi attention. MESSENGER will orbit it 730 times beginning in 2011. 730 chances for the perfect red-carpet photo.

–By Daniel Strain, UC Santa Cruz Science Communication Program