Planetary probe mission
Appears in 2 stories · Last updated Sep 20, 2026
As of September 2026: Source of the surface data used in the study; ended in 2015
Mercury is cooling. Cooling makes it shrink, and new research says it has shrunk more than scientists calculated: up to 23 kilometers of diameter lost since the planet formed 4.5 billion years ago, 10 to 30 percent more than prior estimates.
Updated Sep 20
As of September 2026: Completed 2015; its data underpin the older silica estimates now being questioned
Mercury's surface holds about 37 percent silicon dioxide by mass, up to 25 percent less than earlier estimates. That gap points to a hotter volcanic past, with lava rising from deeper mantle regions melted at extreme temperatures.
Updated Sep 12
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