An ancient magma ocean on Mercury?

Mercury as seen by the MESSENGER spacecraft. Did an ancient magma ocean once cover its surface? Credit: NASA / JPL-Caltech
Mercury as seen by the MESSENGER spacecraft. Did an ancient magma ocean once cover its surface? Credit: NASA / JPL-Caltech

As we have explored the solar system, we have found evidence for different kinds of oceans. Earth of course has its water oceans, while some icy moons like Europa have subsurface water oceans and Saturn’s largest moon Titan has seas and lakes of liquid methane.

Other worlds which may have had oceans in the past, but are now dry, include Mars and Venus. Now it seems that Mercury may also have had an ancient ocean of sorts – of magma, it was reported today.

The new study, by scientists at MIT, suggests that this little planet was once covered by an ocean of magma soon after its formation billions of years ago. The results come from an anlalysis of data from the MESSENGER spacecraft, which is still orbiting the planet. The analysis revealed two different kinds of rock with distinct compositions.

After experiments to recreate the same compositions in the lab, a synthetic copy of the material on Mercury’s surface, it was concluded that the best explanation for their creation on Mercury was a large ocean of magma which created two layers of crystals, then solidified and eventually remelted into magma.

The magma ocean is estimated to have existed probably only within the first 1-10 million years of Mercury’s history, and likely formed by the same impact processes that created the planet to begin with.

According to Timothy Grove, a professor of geology at MIT, “The thing that’s really amazing on Mercury is, this didn’t happen yesterday. The crust is probably more than 4 billion years old, so this magma ocean is a really ancient feature.”

The paper has been published in the journal Earth and Planetary Science Letters. See also the MIT report here.

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Paul Scott Anderson is a freelance space writer with a life-long passion for space exploration and astronomy. He started his blog The Meridiani Journal in 2005, which is a chronicle of planetary exploration. He also publishes The Exoplanet Report e-paper. In 2011, he started writing about space on a freelance basis, and now also currently write for AmericaSpace and He has also written for Universe Today and SpaceFlight Insider, has been published in The Mars Quarterly and has done supplementary writing for the well-known iOS app Exoplanet for iPhone and iPad.

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