Volcanoes on Mercury solve 30-year mystery

NASA spacecraft’s first flyby yields new info about innermost planet


By Andrea Thompson (space.com)

updated 5:23 p.m. CT, Thurs., July. 3, 2008
A NASA spacecraft's first flyby of Mercury has yielded a wealth of information about the innermost planet, some of which confirms volcanism occurred there, settling a longstanding debate.

Information about such planetary mysteries as Mercury's magnetic field and geological history also has flooded in.

"We're really pleased," said Sean C. Solomon of the Carnegie Institution of Washington, principal investigator for the Messenger probe. "[The data] gives us a lot to chew on."


Messenger (short for MErcury Surface, Space ENvironment, GEochemistry and Ranging) made its debut flyby of Mercury on Jan. 14, passing about 124 miles (200 kilometers) over the planet's surface. The spacecraft's instruments took a closer look at the areas seen by the Mariner 10 mission in 1974 and 1975, which imaged about 45 percent of the planet's surface, as well as an additional 21 percent of the surface never before seen by a spacecraft.

In a collection of 11 papers detailed in Friday's issue of the journal Science, mission scientists presented the preliminary findings of the initial flyby.

Volcanism or impact melt?
Volcanism has long been thought to be a major force in shaping the rocky, terrestrial planets. Volcanoes still ravage Earth. On Mars, subdued volcanism may still be alive. Venus is riddled with old volcanoes.

Images of Mercury from the Mariner 10 mission showed areas of smooth plains covering parts of the planet's surface. Scientists speculated that these could be volcanic deposits, similar to the basaltic maria (seas) on the moon. But unlike the maria, these plains were lighter, not darker, than the surrounding landscape. At the time of the Mariner 10 mission, Apollo 16 astronauts had just discovered that similarly light plains on the moon were actually impact breccia, or rock that was smashed apart and then re-welded together again.

The resolution of the Mariner 10 images as well as the angle of sunlight illuminating the features prevented scientists from determining which geological mechanism had created the plains on Mercury.

"That created a stalemate for basically 30 years," until Messenger arrived on the scene, said science team member James Head of Brown University.

The angle of the sun's light on Mercury's features this time around yielded more detail and evidence pointing to volcanic activity. False-color images of the plains and presumed volcanic features showed that they had an orange tint and were "distinctly different from [their] surroundings," Head said.




Messenger images of the Caloris basin, the youngest-known impact basin on Mercury, showed smaller craters within the impact basin that had been filled in with material, "and if you had impact melt [as with the lunar breccia], that wouldn't happen," explained Johns Hopkins University's Scott Murchie, a co-investigator for the Mercury Dual Imaging System.

The small craters likely were the result of impacts in the basin long after it was formed. Later still, volcanic eruptions spewed lava across the basin, all but erasing the smaller craters. Head said this was "clear evidence that you're looking at lava flows."


>>>http://www.msnbc.msn.com/id/25518217/

Interesting I wonder what the people are like there

Mirror, dear, you can always go visit.

Lindyy, I apoligize to you once again for offending you with my "radical" political views. I love you for who you are and I respect your opinions. I just wish you could look past our petty differences and see the things we have in common.

Is that one of those Christian "jokes", or does it come from the heart?