NASA Finds New Evidence of Ice on Mercury

New evidence is the strongest yet that there's ice on Mercury.

This undated handout photo provided by NASA, taken in 2008 by the Messenger space probe, shows a portion of Mercury. Earth's first nearly full look at Mercury reveals that the tiny lifeless planet took a far greater role in in shaping itself than scientists had thought with volcanoes spewing "mysterious dark blue material."

A portion of Mercury shown in an image taken by the Messenger space probe in 2008.

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A probe orbiting Mercury has found more evidence of the existence of water ice at the planet's poles, NASA scientists announced Thursday.

Just don't hold out for life.

Even though there is likely ice on Mercury, it's highly unlikely that even bacterial microbes could survive in the ice, despite recent discoveries that bacteria can survive the bitter cold of subzero Antarctic lakes, says Gregory Neumann, an instrument scientist with NASA's MESSENGER mission. That spacecraft has been orbiting Mercury since 2011.

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"My gut feeling about life on Mercury is that it's a resounding no," he says. "The temperatures at which ice is stable in a vacuum is so low, compared to a relatively warm [-10 degrees F] in Antarctica. The chemical processes just don't operate on Mercury. If anything is going on there it's beyond our realm of understanding."

Using three different instruments—radar, laser, and a neutron spectrometer (which measures atomic movement)—aboard the MESSENGER spacecraft, NASA scientists seem to have confirmed a hypothesis that ice has existed at Mercury's poles for millions of years.

As the planet closest to the sun, Mercury seems like an unlikely place for ice—daytime temperatures can reach 800 degrees Fahrenheit. But the planet has no atmosphere to retain that heat, and its poles never face the sun, meaning temperatures there are constantly cold, reaching temperatures as low at -280 degrees Fahrenheit.

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Though scientists hypothesized as early as 1991 that ice might exist in craters near Mercury's poles, MESSENGER's recent finding is the most convincing evidence to date, says Gregory Neumann, an instrument scientist with the MESSENGER mission. Neumann says that there is likely ice at both of Mercury's poles, and that it exists close to the surface.

"The maximum thickness is probably less than 100 meters, if it was thicker, we'd see landforms similar to glaciers," he says. "What's puzzling is why there are these accumulations on Mercury when we don't see them on the Moon."

Neumann says the ice is likely constantly forming due to hydrogen emitted from the sun.

"The fact that we're seeing it here and it's not covered by dust or boulders means that the process that's putting it there is ongoing," he says.

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MESSENGER is scheduled to continue monitoring Mercury for another year or two before it runs out of fuel and eventually crashes into Mercury's surface. During that time, the spacecraft will get closer to the surface and will likely be able to get a better sense of the makeup of Mercury.

"As it gets lower we'll be able to use our imagers at longer exposures and we'll be able to either confirm or refute our findings," Neumann says.

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Jason Koebler is a science and technology reporter for U.S. News & World Report. You can follow him on Twitter or reach him at jkoebler@usnews.com.