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Hello again, Mercury. This week in a trio of papers Science, the scientists behind the Messenger probe released their findings from the craft’s third and final flyby of the planet closest to the sun, which it executed last September. Mercury, they’ve shown once again, is full of surprises—and they’ll get the chance to explore them when Messenger returns and finally enters Mercury’s orbit in March 2011.

Scientists have now mapped 98 percent of the planet by combining the new observations with the first two flybys in January and October 2008, plus the Mariner 10 mission in the ’70s, [said Brett Denevi, coauthor of one of the papers]. The latest flyby filled in a 360-mile-wide gap that had never been imaged before.

“It wasn’t a huge amount of real estate, but there was a lot of really interesting stuff there,” Denevi said. The most exciting features include a 180-mile-wide basin filled with hardened lava, and a crooked bowl surrounded by glass and magma that may be the largest volcanic vent ever identified on Mercury. Together, these features suggest that Mercury had active volcanoes later in its history than scientists had suspected [Wired.com].

The first image above shows a smooth basin dubbed Rachmaninoff, which is one of the smoothest regions seen on Mercury—so smooth that it must have formed from volcanic material in the last billion years or so. The yellowish part in the upper right of this false color image is that volcanic vent.

Louise Prockter, one of the scientists on the volcanism paper, says the findings suggest a Mercury that was active longer than most scientists thought—perhaps up to one to two billion years ago.

“Until MESSENGER, we had expected Mercury to get rid of all its heat early on in its history because it’s pretty small,” Prockter said. “We’ll want to see if the volcanism we see with this basin was an isolated case or whether it was widespread across the surface, which would have us perhaps rethinking our models of Mercury. It seems that Mercury did not get rid of her heat nearly as efficiently as had previously been thought” [Space.com].

That’s not all. Mercury, the researchers found, also releases fierce magnetic storms.

The September MESSENGER flyby is the first time scientists have documented the buildup of magnetic energy in Mercury’s magnetotail, the magnetic lines of force that form a region shaped like a comet’s tail on the planet’s night side. The magnetotail absorbed 10 times more magnetic energy from the sun than Earth’s magnetotail does. It then dumped that energy in just two to three minutes, compared to two to three hours for Earth’s field [Science News].

Now, the waiting is the hardest part. The countdown to Messenger’s big adventure in March stands at eight months.

Related Content:
80beats: Latest Mercury Pics Reveal Massive Craters & Possible Volcanic Vents
80beats: Space Probe Soon to Study Mercury’s Comet-Like “Tail”
80beats: Mercury Flyby Reveals Magnetic Twisters and Ancient Magma Oceans
80beats: Brand New Postcards From Mercury, Courtesy of Messenger Space Probe

Images: NASA/JPL/Johns Hopkins