Mercury may have harboured an ancient magma ocean
23 February Science Daily
By analysing Mercury's rocky surface, scientists have been able to
partially reconstruct the planet's history over billions of years. Now,
drawing upon the chemical composition of rock features on the planet's
surface, scientists at MIT have proposed that Mercury may have harbored
a large, roiling ocean of magma very early in its history, shortly after
its formation about 4.5 billion years ago.
The scientists analyzed data gathered by MESSENGER (MErcury Surface,
Space ENvironment, GEochemistry, and Ranging), a NASA probe that has
orbited the planet since March 2011. Later that year, a group of
scientists analyzed X-ray fluorescence data from the probe, and
identified two distinct compositions of rocks on the planet's surface.
The discovery unearthed a planetary puzzle: What geological processes
could have given rise to such distinct surface compositions?To answer
that question, the MIT team used the compositional data to recreate the
two rock types in the lab, and subjected each synthetic rock to high
temperatures and pressures to simulate various geological processes.
From their experiments, the scientists came up with only one
phenomenon to explain the two compositions: a vast magma ocean that
created two different layers of crystals, solidified, then eventually
remelted into magma that then erupted onto Mercury's surface.
"The thing that's really amazing on Mercury is, this didn't happen
yesterday," says Timothy Grove, a professor of geology at MIT.
"The crust is probably more than 4 billion years old, so this magma
ocean is a really ancient feature.ÓGrove, along with postdoc Bernard
Charlier and Maria Zuber, the E.A. Griswold Professor of Geophysics and
Planetary Science and now MIT's vice president for research, published
the results in the journal Earth and Planetary Science Letters.
MESSENGER entered Mercury's orbit during a period of intense solar-flare
activity; as the solar system's innermost planet, Mercury takes the
brunt of the sun's rays.
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