Mercury and Earth followed very different paths after they formed. Mercury, the smallest planet and the one closest to the Sun, appears to have cooled relatively quickly. Roughly one billion years after its formation, volcanic activity may already have largely stopped, leaving the planet covered by a solid, continuous rocky crust.
Earth never reached that same state. Its crust remains geologically active, with volcanoes and plate tectonics continuously reshaping the planet. Mercury, by contrast, has been largely frozen in place for billions of years.
Scientists are still working to understand exactly how its volcanic history unfolded and how those early processes produced the world we see today. One of the best ways to investigate that history is by studying the chemical makeup of Mercury's surface. Mercury Has Less Silicon Dioxide Than Expected Researchers from the Max Planck Institute for Solar System Research in Germany and the Universities of Münster and Göttingen, also Germany, have now produced the most precise estimate yet of the amount of silicon dioxide on Mercury's surface.
The findings, published in the journal Planetary Research, reveal an unexpected result. Silicon dioxide makes up about 37 percent of Mercury's surface material by mass, which is up to 25 percent less than previous estimates suggested. Planetary Research is a Diamond Open Access journal, meaning its research is freely available to interested readers.
Silicon dioxide is extremely common on Earth. The compound, made from one silicon atom and two oxygen atoms, occurs in pure form in materials such as sand and is also a major component of volcanic rocks. Basalt, andesite, and granite can contain as much as 75 percent silicon dioxide.
The unexpectedly low amount on Mercury could provide an important clue about how the planet's crust formed. "Our findings suggest that the volcanic rocks on Mercury formed from more deeply melted mantle material than previously assumed," said Christian Renggli, lead author of the new study and head of the "Experimental Laboratory Magma Ocean" research group at the MPS. The mantle is the layer beneath a planet's solid crust.
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