Mercury is small, fast and close to the sun, making the rocky world challenging to visit. Only one probe has ever orbited the planet and collected enough data to tell scientists about the chemistry and landscape of Mercury’s surface. Learning about what is beneath the surface, however, requires careful estimation.
After the probe’s mission ended in 2015, planetary scientists estimated Mercury’s crust was roughly 22 miles thick. One University of Arizona scientist disagrees.
Using the most recent mathematical formulas, Lunar and Planetary Laboratory associate staff scientist Michael Sori estimates that the Mercurial crust is just 16 miles thick and is denser than aluminum. His study, “A Thin, Dense Crust for Mercury,” will be published May 1 in Earth and Planetary Science Letters and is currently available online.
Sori determined the density of Mercury’s crust using data collected by the Mercury Surface, Space Environment and Geochemistry Ranging (MESSENGER) spacecraft. He created his estimate using a formula developed by Isamu Matsuyama, a professor in the Lunar and Planetary Laboratory, and University of California Berkeley scientist Douglas Hemingway.
Sori’s 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.
Mercury’s core is believed to occupy 60 percent of the planet’s entire volume. For comparison, Earth’s core takes up roughly 15 percent of its volume. Why is Mercury’s core so large?
“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 may help point scientists in the right direction. Already, it has solved a problem regarding the rocks in Mercury’s crust.
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SOURCE: Phys.org, Emily Walla