Map of Moon water; blue indicates higher concentrations of detected water molecules. Credit: NASA/Moon Mineralogy Mapper instrument.Here it comes! A veritable tidal wave of discovery on Earth's Moon….

In one short week, NASA's LCROSS (Lunar Crater Observation and Sensing Satellite) mission will quite literally come to an end—a fiery, spectacular end as it deliberately crashes into the lunar South Pole crater Cabeus A in hopes of kicking up enough material for us to detect the presence of water. If you want to see the action as it happens, come up to Chabot Space & Science Center on Friday morning, October 9, 3:00 AM to watch NASA's live simulcast and–weather and the gods of astronomy permitting–the view through Chabot's 36-inch telescope, "Nellie."

In recent months, NASA has been sending a lot of acronyms—excuse me: spacecraft—to the Moon: LRO with it's LROC, LEND, and LOLA instruments; LCROSS (which I've heard some call "LaCROSS," for the record) with its VIS, NIR, MIR, TLP, VSP, NSP—oh, the list goes on!

The fact of the matter is MOON spells "Moon." Whether or not we do end up returning humans to the Moon in the next decade, which is partly what reconnaissance by LRO and LCROSS and their arrays of acro-instrumentation is for, there are still things to be learned about our nearest neighbor in space—and water is the word at present.

Even as LCROSS and its Centaur-booster-rocket-turned-lunar-clobbering-device follow their final fatal trajectory toward Cabeus A, its launch buddy LRO, now in an orbit around the Moon and beginning to send back scientific results and images, may have already detected telltale signs of the wet stuff—which on the Moon won't be wet, but frozen solid, of course; liquid water cannot persist in the Moon's airless environment.

LRO's LEND (Lunar Exploration Neutron Detector) instrument is designed to find signs of water molecules by measuring neutron radiation emanating from the lunar surface. The Moon is constantly bombarded by high energy cosmic radiation, which forms radioactive isotopes in the soil that in turn emit neutrons. By measuring the abundance and speed distribution of the neutrons, details of soil chemistry can be inferred. The presence of light atomic nuclei–in particular the lightest of all, hydrogen, a component of water—in the soil reduces the levels of neutron emission. That drop in neutron radiation is the telltale scientists are looking for.

While LRO scientists want to make further measurements before concluding the presence water ice concentrations, observations from three other spacecraft—NASA's M3 instrument (Moon Mineralogy Mapper) aboard India's Chandrayaan-1 spacecraft and the Cassini and EPOXI spacecraft—have mutually confirmed the presence of water and hydroxyl molecules (hydroxyl is a water molecule missing one of its two hydrogen atoms) in the soils of the Moon, across much wider expanses than the confines of dark polar crater floors.

Cassini and EPOXI made measurements as they flew past the Moon to their respective destinations (Saturn, and a comet), and measurements have been made by M3 from lunar orbit. The detection of water by these spacecraft doesn't mean seas of liquid or glaciers of ice, or even blanketing layers of gaseous water vapor, but rather relatively small amounts of water and hydroxyl molecules attached to, or "stuck to," other materials in the top few millimeters of soil.

This thin "confetti" of water molecules appears to come and go with lunar daytime, forming during the cold, dark two-week-long lunar night and diminishing under the baking light of the Sun.

So, right now, MOON spells water (M3 et al), water (LRO), and possibly more water (LCROSS, on October 9th)—at least, the evidence seems to be mounting!

Neil Armstrong’s left boot print on the Moon—the celebrated ‘one small step’. Credit: NASA
What were you doing 40 years ago, on July 20th, 1969, when the first human foot (booted, not bare) made its impression on the gritty surface of the Moon? That is, if you're over 40 yourself….

I was in Oakland, lying on the green carpet of my family's living room floor, watching our black and white Zenith television set—the kind that would take a minute or so to warm up before delivering the handful of local VHF TV broadcasts within range of our aerial antenna.

Right. It was definitely another era. As archaic as the telecommunications technology may sound to those born after, oh, 1980, it was nevertheless the Space, not Stone, Age…. Never forget, the Apollo 11 landing on the Moon was the culminating moment of the whole adventure that started the Space Age.

It didn't really matter that our Zenith was a b/w set, as all the images from Apollo 11 and the Moon's surface were transmitted in black and white anyway. My eyes were riveted to the TV, the grainy, fuzzy image of the Eagle's landing strut and ladder as yet empty.

"What's taking them so long?" I complained impatiently (I was seven years old). I remember waiting for what seemed a couple of hours for the astronauts to come out.

"They're probably playing poker inside," was my dad's reply. I don't recall if I believed him or not. Finally, there was a booted foot at the top of the ladder, attached to the bulky white and gray form of a human in a space suit—Neil Armstrong, of course. And, history was made—twice: Buzz Aldrin came down the ladder soon after.

Some of you younger crowd may have been born into a world where humans walked on the Moon a long time ago, but I was born around the time it was actually happening. (In fact, I was born the year after the first human went into space; similarly my grandfather was born the year of the Wright Brothers' first aerial success—how time flies….)

On Monday, we not only mark four decades since that singular historic event, we do so at a time when there are plans afoot for humans to step onto the Moon once again.

Several robotic probes have gone Moonward in recent years, paving the way: Clementine, Lunar Prospector, and only last month the Lunar Reconnaissance Orbiter (LRO) and the Lunar Crater Observation and Sensing Satellite (LCROSS) were launched in tandem. LRO will give us our most detailed and comprehensive view of the Moon's surface appearance and conditions to date, and will help to identify future possible landing sites. LCROSS will look for water ice in a crater floor at the Moon's South Pole by impacting it with an empty booster rocket and studying what is blasted skyward. Water on the Moon would be a resource to future human missions far more valuable than gold.

Neil's left boot print is still up there, next to the Eagle's landing foot, most likely as fresh and new looking as when it was made (unless it got bulls-eyed by a one in a million meteorite strike!).

As there is no air, and thus no erosion, on the Moon, the print serves equally well as a monument to that decades-ago venture, or as a logo for the enterprise of our return. Fitting, too, as the Moon could serve as a stepping stone to destinations beyond….