The LCROSS mission - one of the coolest things that NASA has ever done - found ice on the Moon. We expected it; even charbroiled Mercury has ice around its poles. Water ice is the most common compound in the Cosmos. Made of hydrogen, which is as common as tuna-on-rye, combined with oxygen - the next-most-prevalent element that can bond at all, and which promiscuously joins with anything whatsoever - of course H20 lurks virtually everywhere. Our very brains contemplating the matter are essentially gelatinous globs of contaminated water.

This whole chapter started when the Army's Clementine spacecraft orbited the Moon 15 years ago and detected the spectroscopic signature of hydrogen whenever it flew over the permanently dark depressions at the poles. It seemed that ice was there. Several missions since then have mostly confirmed it, but LCROSS's analysis is the most definitive.

As for amounts, the best fit shows 26 gallons' worth in an area of about 30,000 square feet. How concentrated this is, and how easy to harvest by visiting astronauts, remains to be seen.

Everyone seems excited. If usable ice can be extracted, manned landings and longer stays on the Moon suddenly become possible. After all, bringing water to the Moon costs about $50,000 a pound, and you need 8 1/2 pounds for just one gallon of water. Imagine: half a million dollars per gallon schlepped from Earth, and each astronaut chug-a-lugs one of those precious gallons per day. Unacceptable; nobody but a group of idiots would pay for that.

But if water is already there, that changes everything. So now there may well arise a renewed clamor to return to the Moon, this time for something akin to colonization - or at least, much longer stays than the brief two-day visits of the Apollo program.

But should we? President Obama is weighing this very issue right now.

The Moon is not a logical steppingstone to Mars. It's easier and more energy-efficient to go to Mars directly than to have to land on the Moon and then escape its gravity again. The Moon is a colorless, airless, dangerous, radiation-bathed wasteland with absolutely no minerals or resources of any value. Yes, it's got a form of helium that may someday be useful as a future fusion fuel - maybe, and so what? That's not good enough. The place is a bummer.

Finding ice there may now propel us into a Greek-tragedylike situation. It would be like someone telling you about a restaurant in Tijuana that has great cheesecake. You love cheesecake, but you really don't want to go to Tijuana. Once you've heard about it, however, it'll stay in your mind - until events probably eventually unfold to bring you to that creepy place.

Going back to the Moon will carry at least a $200 billion price tag, and probably much more. Is that really how we want to spend our borrowed money?

Someday, major breakthroughs in propulsion may change the equation. Someday, too, our nation may be swimming in cash, looking for inspirational busywork projects. For now, however, only one thing makes sense: Leave the ice alone. It'll keep.