In lunar terms, that is an oasis, surprisingly wet for a place that had long been thought by many planetary scientists to be utterly dry.
If astronauts were to visit this crater, they might be able to use eight wheelbarrows of soil to melt 10 to 13 gallons of water. The water, if purified, could be used for drinking, or broken apart into hydrogen and oxygen for rocket fuel — to get home or travel to Mars.
“That is a very valuable resource,” said Anthony Colaprete, principal investigator of Nasa’s Lunar Crater Observation and Sensing Satellite — or Lcross — which made the observations as it, by design, slammed into the moon a year ago. “This is wetter than some places on Earth.”
The Sahara sands are 2 to 5 per cent water, and the water is tightly bound to the minerals. In the lunar crater, which lies in perpetual darkness, the water is in the form of almost pure ice grains mixed in with the rest of the soil, and is easy to extract. The ice is about 5.6 per cent of the mixture, and possibly as high as 8.5 per cent of it, Dr Colaprete said.
“That is a large number, larger than I think anyone was anticipating,” Dr Colaprete said.
The $79 million Lcross mission piggybacked on the Lunar Reconnaissance Orbiter, which was launched in June last year and has been mapping out the lunar surface for a future return by astronauts. Lcross steered the empty second stage of the rocket, which otherwise would have just burned up in the Earth’s atmosphere, onto a collision course with the moon.
Last October, as it neared impact, the Lcross spacecraft released the empty second stage and slowed down slightly so that it could watch the stage’s 5,600-mile-per-hour crash into a 60-mile-wide, 2-mile-deep crater named Cabeus. A few minutes later, Lcross, quickly transmitting its gathered data to Earth, met a similar demise.
For people who watched the live Webcast video transmitted by Lcross, the event was a disappointment, with no visible plume from the impacts. But as they analysed the data, scientists found everything they were looking for, and more. Last November, the team reported that the impact had kicked up at least 26 gallons of water, confirming suspicions of ice in the craters.
Concentration of water
The new results increase the water estimate to about 40 gallons, and by estimating by amount of dirt excavated by the impact, calculated the concentration of water for the first time.
Also surprising was the cornucopia of other elements and molecules that Lcross scooped out of the Cabeus crater, near the moon’s south pole. Lying in perpetual darkness, the bottom of Cabeus, at minus 370 degrees Fahrenheit, is among the coldest places in the solar system and acts as a “cold trap,” collecting a history of impacts and debris over perhaps a couple of billion years.