A world where your footsteps never fade

“We have found a strange footprint on the shores of the unknown.” -Arthur Eddington

Since the dawn of mankind, we’ve left innumerable footsteps across the lands, as we’ve traveled far and wide across the globe.

(Image credit: Greg Prohl.)

But (with very rare exceptions) these footsteps don’t last. With winds and/or rains abundant all over Earth, among many other phenomena, it’s usually just a brief matter of time until all memory of these footsteps are removed from the shifting landscape.

(Image credit: Byron Jorjorian.)

But what about a world without winds and rains? What about, in fact, a world with no atmosphere at all?

Well, without winds, rains, snows, glaciers, rockslides, or any other way to move and rearrange the dust on the surface of, say, the Moon, it means that when you leave your footprints there, they’re there to stay for an interminable length of time.

(Image credit: Neil Armstrong, of Buzz Aldrin.)

In fact, the only thing we know of that rearranges the grains of lunar sand on the surface of the Moon are when other objects — meteors, asteroids, and comets — strike the Moon itself!

(Image credit: NASA / William Cooke.)

This creates new impact craters, and kicks up lunar dust, which will eventually settle down onto the lunar surface. Over time, and with either a large enough impact or with a large enough number of small impacts, the natural bombardment of the Moon by debris in our Solar System will wipe out our lunar footprints.

But that has not happened yet. Want to know how we know?

(Image credit: NASA, retrieved from here.)

This is NASA’s Lunar Reconnaissance Orbiter (LRO), which has been orbiting the Moon for a number of years now, taking the highest-resolution pictures ever taken of the entire surface of the Moon. Over the course of its mission, it has streamed 192 TeraBytes of data back to Earth.

And you might think to yourself, if you’ve got an unprecedented-resolution camera orbiting the Moon, wouldn’t it be fun to, I don’t know, photograph the old Apollo Moon-landing sites?

(Image credit: Tech e-Blog.)

Although this has been done before with LRO, it has now used the full power of its instruments — specifically the new low-altitude Narrow Angle Camera — to photograph three of the Apollo landing sites with unprecedented accuracy: those of Apollo 12, 14, and 17.

Let’s take a marvelous, detailed look at our first footprints on the surface of the Moon!

(This, and the two subsequent images, courtesy of NASA / LRO / GSFC / ASU. Don’t forget to click on each one for an ultra-hi-res version; up to 2000×1500 pixels in the case of Apollo 12, above!)

How did they do it? They changed the orbit of the LRO so that it would be at an incredibly low altitude as it flew over these landing sites, so much so that the resolution on the above image is less than four meters per pixel! This amazing Apollo 12 image shows not only the physical landing site (marked “Intrepid Descent Stage” on the image), but also the Surveyor 3 probe that had been on the Moon since 1967, visited by the Apollo 12 astronauts two-and-a-half years later!

You can also notice the bright, white “L” shape near the ALSEP equipment label (ALSEP stands for Apollo Lunar Surface Experiments Package, which monitors the Moon’s surface and interior); the “L” is due to very highly reflective power cables that run from the central station to two of its instruments. Even though the cables are much smaller than the size of a pixel, their high reflectivity allows them to show up on LRO’s image.

Finally, you’ll notice the dark depressions that run around and between many of the crater rims, looking like dried-up canals. Those are no canals; those are astronaut footprints! Without any major or nearby meteor impacts over the last 42 years, the footprints are just as visible today as they would have been the day they were created, and here in 2011, we’re looking 42 years back in history and seeing that they haven’t changed at all.

The view of Apollo 14 is less spectacular, but perhaps even more famous. You can still see the descent module and the ALSEP equipment, but nothing else leaps out at you. Well, except for the footpaths once again! Whose are they? Edgar Mitchell and the famed Alan Shepard. At the end of the second Moonwalk, Shepard famously hit those two golf balls, “miles and miles” as he said.

But I’ve saved perhaps the most spectacular image for last.

Apollo 17, where Eugene (Gene) Cernan and Harrison (Jack) Schmitt became the last men to walk on the Moon, paints a notably different picture at this high resolution. Yes, there’s still the descent module on the surface, the ALSEP equipment and the footpaths.

But look closer. There’s also something marked “LRV” (no relation to Abbie) as well as a lighter set of two parallel tracks that run across the surface. Know what they are?

(Image credit: NASA / Jack Schmitt.)

The Apollo Lunar Roving Vehicle! Included on Apollo 15, 16, and 17, its tracks on the surface are distinctly different from human footprints, and allowed the astronauts on those missions to achieve distances far greater than those reached on the earlier missions. The tracks from Apollo 17′s LRV don’t even come close to fitting in this image; they extend for a total distance of over 22 miles, reaching a maximum range of nearly five miles away from the landing site! And, just like the others, these tracks have remained in pristine condition since they were first created forty years ago.

How fascinating, that after 40+ years, humanity’s footprints on the Moon’s sand dunes remain virtually unchanged by the passage of time. They could remain there, unchanged, for millions of years into the future, or an impact from a small, rogue asteroid could wipe them out at a moment’s notice. It’s simply amazing what the still quiet of an atmosphere-free world can preserve!

For those of you who want to see more hi-res pictures of the Apollo Landing Sites taken with LRO’s Narrow-Angle Camera, click on this link and your wish will be granted for all 6 of the Moon-landing missions! NASA has also been kind enough to release a series of videos and interviews about these latest images, so head on over to learn even more about it!

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