Researchers working on NASA's MESSENGER spacecraft have announced major new findings about Mercury, including the discovery that the planet's iron core is much larger than previously thought, and that the surface of the planet is swelling from the inside out, a process that scientists haven't yet explained.
According to data collected by MESSENGER, the core of the planet includes a previously undiscovered solid layer of iron sulfide buried under the mantle. The revelation means that Mercury's core makes up about 85% of the planet, leaving room for only a thin mantle and crust.
And that surface is being shaped by something other than volcanic activity and impact craters. The MESSENGER team noted that, among other rising and tilting areas of the planet's surface, the center of the largest crater on the planet has swelled so much that it is now taller than the crater's walls.
"One of the things this has told us is that there are some unusual dynamics in the interior of Mercury going on that we haven't thought about before and that we don't understand," said MIT planetary scientist Maria Zuber.
The research was unveiled Wednesday at the Lunar and Planetary Science Conference in Houston and will appear in this week's issue of Science.