Mercury's crust composition hints at hotter volcanic era
New measurements show silicon dioxide makes up about 37% of Mercury's surface by mass, up to 25% lower than earlier estimates. This suggests ancient lavas originated from deeper, more extensively melted mantle regions. The findings point to a hotter volcanic interior than previously recognized.
The analysis, led by Christian Renggli at the Max Planck Institute with colleagues from Münster and Göttingen, appears in the open-access journal Planetary Research. Mercury's crust holds roughly 37 percent silicon dioxide by mass, up to a quarter lower than earlier calculations. The planet cooled swiftly, with volcanic activity largely ceasing about a billion years in, leaving a static crust unlike Earth's dynamic one.
As molten mantle crystallizes, silicon dioxide concentrates in remaining liquid, so later lavas typically carry more of it. Mercury's low levels instead suggest lavas tapped deep mantle zones melted extensively at extreme temperatures. A secondary hypothesis holds that the crust originally contained more silicon dioxide but lost oxygen over time.
This finding could reshape models of rocky planet formation, particularly for small worlds near their stars. Scientists studying exoplanets or planning future Mercury missions may adjust expectations about interior heat and volcanic longevity. The open-access publication also makes the data freely available, potentially accelerating comparative research across planetary bodies. For the public, it underscores that even seemingly inert worlds preserve dramatic, unexpected histories.