Leonard David's INSIDE OUTER SPACE

Credit: Rendering by Lior Rubanenko/UCLA

The polar regions of Earth’s Moon may contain significantly more water ice than previously thought, according to new research by space scientists at the University of California, Los Angeles (UCLA).

Shoring up this belief are two decades of observations from telescopes and spacecraft, not of the Moon, but the planet Mercury. What’s been found are glacier-like water ice deposits near Mercury’s poles. 

Why, despite their similar surface conditions, does our Moon have so much less ice than Mercury?

NASA’s Messenger orbiter at Mercury. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Buried below

“The simple answer is that the Moon has lots of ice — it’s just buried below the surface,” said David Paige, a UCLA professor of planetary science and a co-author of the study.

The study, published July 22 in Nature Geoscience, points to the existence of previously undetected thick ice deposits on the Moon. It was led by Lior Rubanenko, a UCLA graduate student.

Parallel investigations conducted on the Moon, whose polar thermal environments are very similar to those of Mercury, found only patchy, shallow ice deposits. Paige said that difference was the impetus for the UCLA study.

Lunar Reconnaissance Orbiter flies over Shackleton crater near the lunar south pole in this computer rendering.
Credit: NASA’s Scientific Visualization Studio

Undetected thick ice deposits

Using data from NASA’s Messenger orbiter at Mercury and NASA’s Lunar Reconnaissance Orbiter spacecraft, researchers measured approximately 15,000 simple craters with diameters ranging from 2.5 to 15 kilometers (about 1.5 to 9 miles) on Mercury and the Moon.

So what’s the lowdown on lunar ice?

“We found that shallow craters tend to be located in areas where surface ice was previously detected near the south pole of the Moon,” Rubanenko said in a UCLA press statement.

According to the study, the most probable explanation for those shallower craters is the accumulation of previously undetected thick ice deposits.

Next step

The researchers conclude by suggesting that future Moon missions include the use of probes that can be used to study the shaded craters to confirm their suspicions.

The UCLA study also suggests that there may be enough water to sustain a future lunar settlement.

“We may use our results to re-estimate the total mass of the ice trapped in the lunar poles. Lunar cold-traps have been previously estimated to occupy ~104 km2. If all cold-traps hide a ~10-m-thick pure subsurface ice deposit, the total mass of water ice on the Moon could be estimated to be up to ~100 million metric tons.”

If true, this is approximately two orders of magnitude greater than previous estimates, the researchers report.

Buried treasure

“Our results combined with previous radar data imply that the most concentrated lunar ice deposits are likely to be buried a few meters under permanently shadowed south polar cold-traps. The possibility that thick ice-rich deposits exist on the Moon may not only help resolve the outstanding question regarding its low ice abundance relative to Mercury, but may also have practical applications in preparation for a future permanent lunar settlement,” the researchers conclude.

The paper – “Thick ice deposits in shallow simple craters on the Moon and Mercury” – has been published in the journal Nature Geoscience, and is authored by Lior Rubanenko, Jaahnavee Venkatraman and David Paige.

For more information on the paper, go to:

https://www.nature.com/articles/s41561-019-0405-8