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The shadow of their lander dominates a mosaic of the numbered photos Neil Armstrong and Buzz Aldrin took out their window before leaving the moon. (NASA/Panorama assembled by R. Farwell for the Apollo Lunar Surface Journal)

Finding Apollo

Forty years later, we’re about to see what the moonwalkers left behind.

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The flag is probably gone. Buzz Aldrin saw it knocked over by the rocket blast as he and Neil Armstrong left the moon 39 summers ago. Lying there in the lunar dust, unprotected from the sun’s harsh ultraviolet rays, the flag’s red and blue would have bleached white in no time. Over the years, the nylon would have turned brittle and disintegrated.

Dennis Lacarrubba, whose New Jersey-based company, Annin, made the flag and sold it to NASA for $5.50 in 1969, considers what might happen to an ordinary nylon flag left outside for 39 years on Earth, let alone on the moon. He thinks for a few seconds. “I can’t believe there would be anything left,” he concludes. “I gotta be honest with you. It’s gonna be ashes.”

There are other signs of aging at Tranquillity Base. The shiny gold foil on the base of the lunar lander is shiny no more—it would have darkened and flaked away long ago. The once-white life support backpacks, tossed out unceremoniously after Armstrong and Aldrin made their brief spacewalks, have likely turned yellow. The TV camera, the seismometer, the discarded hammer—anything made of glass or metal—are probably okay. And the famous bootprints? They may still be as crisp as the day they were made. Or, they may have the thinnest coating of dust from small grains moving around continually on the lunar surface (see “Stronger than Dirt,” Aug./Sept. 2006).

The truth is, no one knows exactly what the Apollo landing sites will look like after four decades. Nobody thought it would take us this long to go back.

And now we are.

New cameras in orbit around the moon have begun returning photos of sights unseen in a generation. Japan’s Kaguya spacecraft, which arrived in lunar orbit in October, Dave Scott and Jim Irwin’s rocket engine as they touched down in Mare Imbrium in July 1971. They and other Apollo moonwalkers routinely photographed the white patches when they looked back at their landing sites from lunar orbit before returning home. Kaguya’s best camera has a resolution, or ability to separate two objects, of 10 meters (33 feet)—just enough to make out the white patch of disturbed soil. The camera can’t quite resolve the squat, 30-foot-wide base of the Apollo 15 lander sitting in the middle of that patch. But the Kaguya photo shows a dark feature that may be the lander’s shadow.

Until Kaguya, there hadn’t been a camera good enough to spot Apollo artifacts on the moon since the last astronauts left, in 1972. Neither the U.S. Clementine nor the European SMART-1 moon probes, launched in 1994 and 2003, respectively, had enough resolution. (In case you’re wondering, even the best ground-based telescopes can’t make out Apollo hardware on the moon. They have the resolution—some produce sharper images than the Hubble Space Telescope—but the objects left by the astronauts aren’t bright enough to be seen.)

So it’s a job for lunar orbiters. Next up is Chandrayaan, India’s first planetary science spacecraft, which is due to arrive at the moon this fall with a camera twice as sharp as Kaguya’s. That should be good enough to see more than smudges in the dirt, according to Mark Robinson, a planetary scientist at Arizona State University whose own high-resolution camera will fly on NASA’s Lunar Reconnaissance Orbiter (LRO) in November. “I will be surprised if Chandrayaan can’t detect the [lunar landers],” says Robinson. The bases of the landers, six of which are still on the moon, will be only about two picture elements, or pixels, across in the five-meter-resolution images—not enough for clear identification. But in photos taken at low sun angles, says Robinson, the landers’ shadows should appear as dark streaks up to 10 pixels long. This technique has paid off in the past. Long before the first Apollo landing, scientists studying photos taken by the Lunar Orbiter 3 spacecraft noticed a shadow cast by the Surveyor 1 robot, which had landed on the moon eight months earlier.

If the Chandrayaan scientists are “really, really lucky,” says Robinson, they might also detect the shadows of the lunar rovers, the two-man buggies that astronauts left at the Apollo 15, 16, and 17 sites. The 10-foot-long rovers would be less than a pixel in size, but their shadows could be as long as four or five pixels, says Robinson.

His own instrument on the LRO will do a thorough job of “revisiting” the Apollo sites, beginning in early 2009. The narrow-angle camera can resolve details about the size of a microwave oven. As the LRO spacecraft orbits from pole to pole and the moon turns slowly beneath it, it will eventually get a look at all six Apollo landing sites. The resulting pictures should clearly show the landers and the rovers, says Robinson. Even some of the larger experiment packages left behind by the moonwalkers might be identifiable from their shadows. The LRO images should also show rover tracks and the dark areas where the astronauts scuffed up the lunar soil. The new information can then be used to refine maps of the moonwalkers’ historic traverses.

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