Strange features on Mercury upend thinking about ‘first rock from sun’

Posted on March 23, 2012


New results from NASA‘s MESSENGER spacecraft reveal craters with tilted floors. In one large basin, half of the basin floor sits higher than the basin’s rim. A vast volcanic plain sports a tall, broad lump, with no obvious source for the rise. The planet’s interior is dominated by a core structured vaguely like a peanut M&M – a solid-iron center, a molten iron layer, covered with a thin, dense shell. And Mercury’s equator traces a slight ellipse, rather than a circle.

All in all, the first spacecraft to orbit Mercury is revealing the planet with many features unlike anything researchers have seen anywhere else in the solar system.

After looking at MESSENGER’s data so far, “I understand far less than I used to” about Mercury, says Maria Zuber, a planetary scientist at the Massachusetts Institute of Technology in Cambridge, who leads a team analyzing the planet’s surface features. “But I know more.”

One key message: Mercury has been geologically active through far more of its 4.6-billion-year evolution than previously thought.

Mercury is the solar system’s munchkin planet – slightly larger than the moon. Given its size, “there was good reason to believe that Mercury cooled off early, and there hasn’t been much of anything going on for most of its history,” Dr. Zuber says. But the evidence the team has gathered suggests that the broad, oddly deformed features they see in the planet’s northern hemisphere were formed when the planet was well into middle age, she says.

CS Monitor

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