New estimates of Mercury’s thin, dense crust and its relatively large core

This image of Mercury was created using infrared, red and violet filters that capture wavelengths both visible and invisible to the human eye; the colors shown here are only slightly different from what the human eye would see. Source: NASA/Johns Hopkins University APL/Carnegie Institute of Washington

Maybe giant impacts or solar winds stripped away a lot of its stony body

Mercury is one of our solar systems’ terrestrial planets made of stone and metal ore. It is small, has the fatest orbital speed and is close to the sun, making this rocky world challenging to visit. Only one spacecraft has ever orbited the celestial body and collected enough data to tell scientists about the chemistry and landscape of Mercury’s surface.

After Nasa’s Messenger mission ended in 2015, planetary scientists estimated Mercury’s crust was roughly 22 miles thick. Now, scientist Michael Sori from the University of Arizona disagrees: he estimates that the crust is just 16 miles thick and is denser than aluminum.

His estimate supports the theory that Mercury’s crust formed largely through volcanic activity. Understanding how the crust was formed may allow scientists to understand the formation of the entire oddly structured planet. „Of the terrestrial planets, Mercury has the biggest core relative to its size,“ Sori said.

Its core is believed to occupy 60% of the planet’s entire volume. For comparison, Earth’s core takes up roughly 15% of its volume. Why is Mercury’s core so large?

The terrestrial planets of the Solar System: Mercury, Venus, Earth, and Mars, sized to scale. Source: Wikimedia Commons

„Maybe it formed closer to a normal planet and maybe a lot of the crust and mantle got stripped away by giant impacts,“ Sori said. „Another idea is that maybe, when you’re forming so close to the sun, the solar winds blow away a lot of the rock and you get a large core size very early on. There’s not an answer that everyone agrees to yet.“

Sori’s work has also solved the problem regarding the mysterious rocks in Mercury’s crust.

The full article is available on the University of Arizona’s webpage.

Sori’s scientific study „A Thin, Dense Crust for Mercury“ was published in Earth and Planetary Science Letters.

The United States Geologic Survey released this topographic map of Mercury in 2016. The highest elevations are colored red, and the lowest dark blue. Source: USGSThough Mercury may look drab to the human eye, different minerals appear in a rainbow of colors in this image from NASA's Messenger spacecraft. Source: NASA/Johns Hopkins University APL/Carnegie Institution of Washington

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(02.05.2018, USA: 05.02.2018)