Planetary probe mission
Appears in 2 stories · Last updated Sep 20, 2026
As of September 2026: Will test the revised contraction estimate with high-resolution data starting November 2026
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: Approaching Mercury; orbit insertion scheduled November 21, 2026
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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