Simulations Link Mercury’s Polar Ice to 17-Km-Class Impact, Trapping Over One-Fifth of Water
Updated
Updated · New Scientist · May 22
Simulations Link Mercury’s Polar Ice to 17-Km-Class Impact, Trapping Over One-Fifth of Water
4 articles · Updated · New Scientist · May 22
New models suggest Mercury’s polar ice was deposited in a single impact event about 100 million years ago, when an icy, rocky body likely formed Hokusai crater and briefly created a water-rich atmosphere.
Just over one-fifth of the impactor’s water vapor could have migrated into permanently shadowed polar craters within one Mercurian day—176 Earth days—matching MESSENGER observations better than earlier estimates.
The study says a larger, slower impactor than previously proposed would preserve even more water on the surface, helping explain why Mercury retains substantial polar ice despite daytime temperatures above 430°C.
That mechanism may also clarify why Mercury has far more polar ice than the moon, which is otherwise similar but apparently lacked a comparable recent water-delivery event.
BepiColombo, due to enter Mercury orbit later this year, could help test how those ice deposits record water delivery across the inner solar system, including Earth.
How could Mercury's temporary atmosphere deposit so much water at its poles before being stripped away into space?
Why is Mercury's single-impact water unique, when the Moon also holds billions of tons of ice in its craters?
Beyond water, what other life-essential materials might this single catastrophic impact have delivered to Mercury's poles?
Did One Giant Impact Deliver All of Mercury’s Polar Water Ice? New Evidence and Implications (2026)
Overview
Recent research has transformed our understanding of Mercury's polar water ice, shifting from the old idea of slow, steady delivery to a new focus on rapid accumulation. This change is driven by evidence that the ice deposits are surprisingly young, around 100 million years old, which challenges gradual models like solar wind or micrometeoroid accretion. Scientists now believe that a single, large impact event could have quickly delivered most of Mercury's polar ice. This breakthrough, published in 2026, highlights how one dramatic event may explain the planet's youthful, pure ice deposits and opens new directions for future exploration.