If extraterrestrial intelligence has visited the moon, there may be signs of their activities. Or, at least, astrophysicist Paul Davies and his student Robert Wagner seem to think so. In a paper published in Acta Astronautica, Davies and Wagner argue that scrutinizing the surface of the moon for extraterrestrial artifacts may prove beneficial in the search for extraterrestrial intelligence (SETI). They argue this can be archived with the data from NASA’s Lunar Reconnaissance Orbiter (LRO). The mission of the LRO is to serve as a lunar mapping program to flag potential landing sites and characterize the radiation environment, among other things. LRO has the capability to obtain photographs of the lunar surface up to 50 centimeters per pixel using the Narrow Angle Camera (NAC, see Figure 1). The high resolution is required to provide the greatest sensitivity for a correct detect, and mitigate cases like the Martian face. Davies and Wagner believe the hundreds of thousands of photographs provided by NAC can be capitalized for SETI, much like IRAS and WISE have been.
To further bolster their claim, the authors contemplate the types of extraterrestrial artifacts (ETAs) that would persist through the regolith on the lunar surface. They largely consider four classes of artifacts:
- Messages, or artifacts designed to be found and interpreted by an intelligent species,
- scientific instruments, or observational devices sent across interstellar space (e.g. probes) or remnants of an alien expedition to the moon with potential functionality,
- trash, or objects left behind by alien expeditions without any regards to its survival (e.g. radioactive waste, spacecraft remnants), and
- geo-engineering structures, or changes to the moon due to alien activities (e.g. mining or construction).
The most attractive scenario for Davies and Wagner would be for aliens to have left a message a few million years ago. They argue anything older than this would be buried on the moon or have been destroyed by meteoric impacts. Such a message could be near an existing landmark on the moon or have a “radio beacon”. On the case of scientific instrument, the search would most likely favor a search for electromagnetic emissions as opposed to a photographic search. The authors note they have searched the poles for signs of “alien solar arrays” and nothing has been identified yet. Robust searches for extraterrestrial trash or geo-engineering would require something other than photography. However, Davies and Wagner argue potential searches include near lava tubes (for trash) and for artificial topographic features (e.g. open-cast mine). Perhaps the most important outcome is the extent of the search. While only 25% of the lunar surface was imaged at the time, the authors have only been able to automate the search for simple pits. They emphasize the need for crowd-sourcing and citizen science (like the now defunct Moon Zoo) in this endeavor as we do not know a priori what to look for.
While it is a benign project, the premise belongs in science fiction. Davies and Wagner present a very anthropocentric view on ETAs, going so far as to consider “a simple capsule … with a … splash of paint” and “round, open-cast mine[s]” to argue for some of their unorthodox targets. It would appear they want to search for human-like aliens. If we ascribe such human features to them, then perhaps we should consider other searches for them (see Table 1). Freitas Jr. has presented a new approach to SETI in searching for probes that includes the moon and other parts of our Solar System. With all this talk of ETA, this blogger is reminded of a cartoon (see Movie 1) where the strange observations of the moon led to the discovery of a sub-lunar city of Martians. It seems so outlandish, but if we are using our imagination to guess aliens are or have been on the Moon, why stop at the surface? If we consider aliens that are so advanced as to have explored the moon, why should anything they leave be obvious to us on the surface? As with SETI, the lack of data is a problem and makes this search worth a modicum of effort, however tepid and benign the results may be.
|Small -instrument visual/photometric artifact searches of Earth-Moon libration orbits to mag. +18|
|Infrared search for “warm” artifacts (T ³ 50 K) in Earth-Moon libration and solar polar orbits|
|Radar search for small artifacts in Earth-Moon libration and solar polar orbits (Goldstone, Arecibo)|
|Continuing ad hoc beacon searches at various radio frequencies, employing as many new and different search procedures as can be devised|
|Large-instrument artifact search of Earth-Moon libration and solar polar orbits to mag. +25|
|Large-instrument ecliptic survey to mag. +20/+25, looking for evidence of incoming fusion braking rockets, solar sails, interstellar ramjet plumes, laser pushbeam backlighting, or relic corner reflectors|
|Proposed NASA Ames/JPL extrasolar radio beacon survey to 100-1000 light-years, using 109 channel MCSA at waterhole frequencies|
|Beam call signals toward Earth-Moon, Earth-Sol, and Jupiter-Sol libration orbits, and solar polar orbits, using waterhole and other appropriate SETI frequencies|
|Unmanned photographic/sampler probe to Earth-Moon libration orbits. looking for ET artifacts|
|Unmanned photographic/sampler probe to Earth-Sol libration points, looking for ET artifacts|
|Unmanned lunar orbiter/lander, surface mapping and artifact search|
|Unmanned photographic/sampler probe to Jupiter Sol libration points, looking for ET artifacts|
|Extended MCSA radio beacon surveys to 1000 light years, across 1-100 GHz|
|Unmanned mobile Mars lander and orbiter/lander to Martian moons, surface mapping and artifact search|
|Unmanned mobile lander/orbiter to inner planet, outer planets and moons, surface mapping and artifact search|
|Manned exploration of Earth’s Moon, surface mapping and artifact search|
|Full ground-based Cyclops/Orbital Cyclops/”Lunarcibo” radio beacon search to high sensitivity out to 1000-10,000 light-years|
|Full ground-based Cyclops/Orbital Cyclops/”Lunarcibo” eavesdropping search to high sensitivity out to 10,000 light- years for Type I civilizations, intergalactic range for Type II civilizations|
|Unmanned mobile lander/orbiter probes to Asteroid Belt, surface mapping and artifact searches|
|Manned exploration Of Mars and Martian moons|
|Manned exploration of inner, planets, outer planets and moons|
|Manned exploration of the Asteroid Belt|
|DISPATCH HUMAN-BUILT STARPROBES TO EXTRATERRESTRIAL SOLAR SYSTEMS|
|MANNED INTERSTELLAR EXPLORATION|