Ice on the moon.

Scientists say there"s enough water on the moon to support a lunar colony for 100 years. Are your bags packed, or is that just lunar-cy?

As you start to ponder your future, you may want to consider an option that no one--absolutely no one--has ever had before in human history. "Some of you reading this--I guarantee it--are going to live and work on the moon!" says Alan Binder, NASAs chief investigator of Lunar Prospector, a spacecraft that has been orbiting the moon since January. Is Binder a space cadet? Or should you get ready for moon malls?

Hanging out on the moon may have just gotten one step closer to reality. Thanks to the data Lunar Prospector immediately began to transmit to NASA centers in California and New Mexico, scientists soon discovered an amazing find: stores of water concealed in craters on the moon's north and south poles! "Water is the key resource that will support life as well as travel from the moon to the planets," emphasizes William Feldman, a Prospector investigator at Los Alamos National Laboratory in New Mexico. The historic discovery has space fanatics drooling over visions of a moon colony in the 21st century.

Of course, the water isn't readily handy in plastic Evian bottles. It's ice, mixed in with lots of lunar soil. Binder estimates that from 10 to 300 million metric tons (2.6 to 26 billion gal) of frozen water lie scattered across the poles. Theoretically, if collected and melted, the water could fill 15,000 Olympic-sized swimming pools.

Binder and his colleagues at NASA's Ames Research Center in Mountain View, California, have even calculated how long lunar water supplies might last if they aren't recycled--recycling is a must on the moon. Consider that the typical American uses 380 liters (100 gal) of water daily for drinking, cooking, bathing, and washing. At that rate, 33 million tons (7.2 billion gal) of lunar water could support 2,000 people on the moon for more than 100 years, Binder says.

He even formulated a simple recipe for extracting the ice from the rocky soil, known as regolith. The process is called sublimation--converting a solid to vapor. "Put the ice-soil mixture in a closed chamber, warm it up, and the ice will evaporate," Binder says. "Then condense the vapor to form liquid water. It's that simple."

What's more, when broken down into hydrogen (H) and oxygen (O)--the two elements (basic chemical components) that make water ([H.sub.2]O)--the liquid could also be used to help produce rocket fuel, Binder says. These space dreams might one day become a reality.

PROSPECTOR'S FIND

Lunar Prospector carries no astronauts, and won't even touch down on the moon's surface. The drum-shaped orbiter doesn't sport a single camera on board; it sends no pictures back to Earth, unlike Mars Global Surveyor, which has flashed back thousands of photos of the Red Planet's terrain (see SW 10/6/97, p. 8). So how did the spacecraft zoom in on the moon's water in the first place?

Prospector is equipped with five high-tech instruments designed to map the entire lunar surface for the first time ever (see diagram above). The moon map should resolve age-old questions about the moon's resources, structure, and history.

With the discovery of water, Lunar Prospector's neutron spectrometer is an overnight superstar. Instead of collecting samples, the instrument scans for a "signature," or sign, of water. In this case the signature is hydrogen, the element that combines with oxygen to form water.

Here's how the neutron spectrometer scored a hit: Cosmic rays, streams of radiation from the sun and the rest of the galaxy, constantly bombard the moon's surface. When they do, they dislodge neutrons, subatomic particles from elements in the moon's rocky soil.

"The neutrons bounce all over the moon like ping-pong balls," says David Lawrence, a research associate at Los Alamos National Laboratory. When they collide with heavy elements like iron on the lunar surface, the neutrons bounce off fast, like ping-pong balls ricocheting off billiard balls. But when they strike hydrogen, an extremely light element, "they slow down very quickly," like ping-pong balls hitting other ping-pong balls, Lawrence says.

Near each lunar pole, the neutron spectrometer detected a drop in the number of neutrons. "The only thing that can slow down those neutrons is hydrogen," says Binder. The presence of hydrogen set off alarm bells: Hydrogen, in high concentration, most likely points to water. "We will have to sample [the soil] before we absolutely know for sure," cautions Binder.

LUNAR ICE

Where did the moon get its ice? Scientists theorize the water was most likely "delivered" by comets--giant balls of dust and ice that have repeatedly smashed into the moon's surface ever since it formed 4.5 billion years ago. The comets' impacts gouged out massive craters, bowl-shaped holes pitting the lunar surface.

Binder and others suspect most of the moon's ice evaporated instantly when exposed to the sun's rays. After all, temperatures near the moon's equator can climb to 127 [degrees] C (260 [degrees] F). But some ice lies in dark craters near the north and south poles, where temperatures plunge to -190 [degrees] C (-310 [degrees] F). And concealed in these craters lay the water-ice, until Lunar Prospector blew its cover this past March. "Some craters at the poles are so deep, they never see the sun," explains Lawrence.

TAP WATER?

Many scientists around the world are elated about prospects of water on the moon, particularly the wealth of information the ice could reveal about the age and formation of the moon's craters. But many remain skeptical about being able to tap the water.

For one thing, "there are no [large] blocks of ice mixed in with the dirt," says Louis Friedman, executive director of the Planetary Society, an organization of space-exploration supporters. In areas where ice is found, it makes up only 0.3 to 1 percent of the moon's soil. That's like mixing a gallon of water into a ton of dirt. "You'd have to collect soil over hundreds of square miles to find a sizable amount of ice," Friedman says.

Binder likens the challenge to prospecting for gold. "Gold mining involves grinding down a ton of rock until you get an ounce of gold. If it's valuable enough, you do it," he says. "Water on the moon is that valuable."

But even if you could extract a respectable amount of ice, Binder and others admit that inventing technology to operate at sub-zero temperatures would be daunting. Another obstacle would be the means and high cost of transporting water from the poles to proposed lunar bases at the equator, thousands of kilometers away. Some scientists are already trying to tackle these problems--on paper.

"The moon would be a great place to learn how to live on another planet, like Mars," says Lawrence. Picture the moon as the coolest science lab in the universe, where you can delve into physics, astronomy, human physiology ... you name it! In addition, a one-way trip to the moon takes only three days--just in time to shuttle home for the weekend.

In the meantime, Lunar Prospector's mission is far from over. Over the next 14 months, the spacecraft will keep mapping the moon's surface and beam data to Earth. During its last six months in orbit, it will drop to within 9.6 kilometers (6 mi) of the lunar surface and peer into craters for a closer look at lunar ice. At the end of its mission, Lunar Prospector will run out of fuel and crash headlong into the moon.

Binder predicts that humans may return to the moon within 10 years to sample lunar ice for themselves. Who knows? You might be one of the first astronauts to slurp moon juice, lick a moonpop, or ski down the slope of an ice-slicked crater. Better brush up on your moon walk!