TOPICS > Science

Water on the Moon

March 6, 1998 at 12:00 AM EDT


PHIL PONCE: Yesterday, NASA scientists announced evidence of water on the moon. With us now is Alan Binder, the mission’s principal scientist. Welcome, Mr. Binder. Mr. Binder, water on the moon, where is it?

ALAN BINDER, NASA: Absolutely. It’s at the North and South Poles.

PHIL PONCE: And why only on the poles? Why isn’t it throughout the moon?

ALAN BINDER: Well, the only way water can be preserved on the moon, which has no atmosphere, to be in extremely cold areas. The only areas that are cold enough to preserve the water are craters in the near vicinity of the pole where the temperatures are only 80 degrees Calvin, or minus 190 degrees Centigrade. Temperatures any higher, the water simply evaporates.

PHIL PONCE: So the waters in the craters, is it on the surface, are they blocks–is it blocks of ice? Is it underground? How would you describe it?

ALAN BINDER: Well, it’s dispersed as ice crystals or frost, if you will, in the outer about two meters or six feet of the lunar soil. It’s not ice in the terms of patches of ice or ice cubes or sheets of ice. It’s just small ice crystals dispersed in the soil, itself.

PHIL PONCE: Now, NASA estimates that there are about 7 billion gallons of water that you think might be available on the moon. How much is 7 billion gallons of water? Is that Lake Tahoe? Is that Lake Michigan? Is that Lake Champlain?

ALAN BINDER: Well, it’s a relatively small lake, and if those numbers hold–and I’ll discuss that in a moment–that figure is equivalent to a small lake about two miles on the side, about four square miles, and about thirty-five feet deep. That’s a modest amount in terms of terrestrial water, but it’s a lot of water for the moon and for the development of the moon. However, I would like to emphasize, while we’re certain there is water on the moon, our results are very early. We have just had one month’s data. We, as you know, have 17 more months to go, and those numbers will be refined. So right now we are not saying we know exactly how much water is there. Those numbers will get better with time. We’re just saying we know it is there.

PHIL PONCE: And how do you know that? What makes you so sure?

ALAN BINDER: Well, we flew an experiment called the Neutron Spectrometer. And basically, it works this way. Cosmic rays continually bombard the moon, and when they do and they hit the surface, they cause neutrons to be formed. The presence of water diminishes a number of neutrons that are released from the moon. And so, as we fly across the moon, when we reach the polls, we find a diminished number of neutrons coming from an area about 20 degrees wide. That’s a clear signature that water is present.

PHIL PONCE: So, I mean, make sure I understand it. The Lunar Prospector has these instruments on board. The Lunar Prospector is orbiting the moon, and it can measure hydrogen. It can detect the sense of hydrogen–the presence of hydrogen, which, of course, is one of the elements of water.

ALAN BINDER: That is correct. It’s an inference that the hydrogen is bound as water, but, of course, from the standpoint of the abundance of elements in the cosmos, usually hydrogen is bound up in water in this type of environment. So we’re quite sure that it is water ice. But obviously, as I said before, we don’t yet know exactly how much. That will come as the measurements are refined.

PHIL PONCE: And where did this water ice come from?

ALAN BINDER: Well, the moon, itself, was born very, very hot. All the water, all the volatile elements were simply boiled away from the moon. We know that from the Apollo samples, which were brought back over 25 years ago. However, since the moon was formed, it’s been constantly bombarded by comets and meteorites, forming many of the craters we, of course, see with telescopes, while a comet, as I think you know, consists mainly of water. And while most of that water would simply be blasted away during the impact, some of it will remain in the lunar environment and can be transported to the polar regions, where it would freeze out. So this is water brought to the moon during the last 2 billion years.

PHIL PONCE: So comets are sort of like dirty snowballs.

ALAN BINDER: They certainly are.

PHIL PONCE: That was one description I read.

ALAN BINDER: That is a very good description, yes.

PHIL PONCE: And why is it a big deal that you’re finding water on the moon, or confirming it in this amount?

ALAN BINDER: Well, as I mentioned, the moon simply does not have water of its own. And this was one of the disappointments when we brought the samples back during the Apollo era. Water is clearly necessary for human life. We need it for life support. Secondly, water can be broken down to oxygen and hydrogen, which is the most efficient propellent for rockets. And so the absence of water meant that we would have to take every bit that we would need for life support, and the absence of water also meant we did not have a fuel. Well, now we know that is there. So we can move ahead with the exploration of the moon, set up a lunar base, and I expect we’ll set up a lunar colony, and the water is there to be used. If that were not the case, we have to take all that water with us. And since it costs on the order of a thousand dollars to ten thousand dollars per pound to take anything to the moon, every drop of water you take to the moon costs a tremendous amount of money.

PHIL PONCE: And when you talked about the use of water as a fuel, that’s because hydrogen and oxygen is one of the propellants in some of the spacecraft?

ALAN BINDER: That’s correct. That’s correct.

PHIL PONCE: Water is also a sign of life. Does this indicate that maybe there’s some frozen bacteria under the surface of the moon?

ALAN BINDER: No. Again, the moon’s environment, itself, was totally hostile from its origin to the formation of life. And while comets and carbonaceous condrite meteorites–those that do contain some water–do contain organic molecules in relatively high abundances, when a meteorite or a comet hits the moon, it is totally vaporized. And those compounds are destroyed. So all we have left are the remnants of the water that was brought there from the comets. However, I’d like to say that the presence of water doesn’t mean that there was life on the moon, or could be life on the moon in the past, but what it does mean is we can take life, i.e., ourselves to the moon and live there and work there. So it will enable the moon to have life.

PHIL PONCE: Mr. Binder, you described the water on the moon as a type of frost mixed in with the soil. How would you extract it?

ALAN BINDER: Well, quite simply, as I mentioned earlier, the water is preserved only because of the extreme cold temperatures. If the polar regions were just a little bit warmer, for example, if the sun did shine in the east crater, the water would simply, the water ice, I should say, should simply evaporate, so all we have to do to recover it is dig it up, put it in a chamber, raise the temperature a few tenths of a degree–or to even room temperature if you wanted to, and the water will evaporate, and then you collect it just to cool it down and just like frost or dew form in the morning, you can rinse it out, and so it’s a relatively simple process.

PHIL PONCE: And viola, moon river.


PHIL PONCE: And voila, moon river, Mr. Binder.

ALAN BINDER: That’s correct.

PHIL PONCE: Thank you very much.