6. Seeking artifacts using current data
The best available visible-light imagery of the moon
comes from the Narrow Angle Camera (NAC) on the Lunar
Reconnaissance Orbiter, which has been orbiting the
moon since mid-2009 [7]. It has imaged over 25 percent
of the lunar surface at resolutions down to 50 cm/pixel, in
a variety of lighting angles. This dataset is so good that
several artifacts have in fact already been found, in both
the Instrument and Trash categories. However, all of them
were created by humans. These artifacts include not only
the Apollo landing sites, which are easily identified by the
thin dark trails of dust kicked up by the astronauts, but
also all of the NASA and Soviet unmanned probes, which,
with the exception of the two soviet rovers that left
kilometers-long tracks, have nothing to mark their location
but their slightly odd-looking shadows, and sometimes
a small halo of disturbed dust from the landing
rockets. However, in all of these cases, the people who
found the artifacts already knew approximately where to
look, so they only needed to comb through a few NAC
images before they found the lander or rover they were searching for. For alien artifacts, we don’t have the luxury
of knowing what latitude and longitude to target, so we
need to study the entire surface. Focusing on some
regions of special geological interest would help, but
there would still be hundreds of images to look through.