Searching for Monoliths: When Science Fiction Informs Science Reality

In 1999, American satellites in orbit around the moon detected a strange magnetic anomaly emanating from within the crater designated Tycho. An early explanation for origin of the anomaly source was a ferrous meteorite, but that could not account for the strength of the produced magnetic field. A few years later in 2001, an expedition to the anomaly site was dispatched from the lunar base at Clavius. The team was led by astrophysicist and former chair of the US National Council of Astronautics, Dr. Heywood Floyd. The expedition revealed a structure, in more ways than one similar to a black box, with rectangular prismatic dimensions in the ratio of the squares of the first three nonzero natural numbers. This ratio held even when the distances were measured at the finest resolution afforded by modern instruments. Subsequent radioisotopic dating of the surrounding regolith implied that the structure had remained in place for some three million years, long before any lunar activity attributable to any human nation and in fact older than the genus \textit{Homo} itself. Given its age and unnatural design, scientists were led to conclude that the object is not of this world nor of this solar system, but actually an emissary of some advanced extraterrestrial civilization sent to monitor the development of the human race.

Does it sound like science fiction? The above story is indeed fictional and is actually lifted from the plot of 2001: A Space Odyssey, a film and novel by Stanley Kubrick and Arthur C. Clarke (which itself is influenced by Clarke’s earlier short story The Sentinel). However, this is fundamentally the type of object that SETI scientists are now seriously contemplating searching for! (As such, we should be mindful of the great ideas that have come to us from science fiction.) Setting aside great storytelling, one of the core ideas of this film was that the Earth had been visited in the remote past by an alien intelligence who established and left behind artifacts after their survey of the solar system was complete. Whether the artifacts were left deliberately or otherwise inadvertently is less important as is the fundamental question of whether or not it is possible for us to perform an exhaustive search for them. In 2013 (nonfiction timeline), Davies & Wagner suggested exactly this kind of search and also overviewed the kinds of strategies we might use to detect a variety of signatures which would suggest that the Moon had been visited in the remote past. These strategies revolve around searching through the Lunar Reconnaissance Orbiter (LRO) data, which offers high resolution imaging of the lunar surface. In this way, SETI science can “piggyback” off the gains of traditional science, which often acquires data that can dually be utilized for SETI purposes. (Imagine the difficulty of justifying a complete surface map of the Moon for the explicit purpose of searching for alien artifacts in a mission proposal to NASA!) With the LRO data, we are afforded the ability to search for 1-10m class objects which could be the detritus, message-carrier structures, habitats, or instruments of a past alien visitation.

This paper is the logical continuation of the Bracewell 1960 paper applied to the specific case of stationary (possibly perpetually ensconced by craters or more likely subterranean) artifacts on or near the surface of solar system bodies. (The original paper did not deal with this case, but focused more on probes in orbit, which was later expounded upon by Freitas 1983.) In my reaction to Bracewell, I suggested how a search for exposed artifacts on the surface of solar system bodies could be a feasible project given modern artificial item recognition software and machine learning algorithms. However, as the authors point out, there are difficulties with the lifetimes of exposed structures given that any region on the surface of the Moon, for example, is likely to be struck by impactors on vast geological timescales, releasing energies which no known materials would be immune to. This problem arises since the progenitor civilization is expected to be truly primordial given the expanses of cosmic time, and hence their probe is likely to be millions or possibly even billions of years old. Therefore, the artifacts would probably be buried and a subsurface search conducted with penetrating radar or by a human expedition is motivated for the future. For the present however, we are limited to “relatively” recently deposited surface objects which could have been picked up in the LRO survey maps. To process this vast amount of data presents another issue, since although it could be processed without automation, it would probably require tens of thousands of man-hours to sift through it all. The cost and upkeep of such an effort would obviously defeat the purpose of a low-cost, low-effort SETI search. In the case of automation however, machine learning algorithms are limited to identifying only those objects on which it is trained to identify. For example, a machine may be exquisitely capable of identifying particular geometrical shapes, but who is to say that an artifact need be perfectly geometrical? And what of partial or nearly complete obscuration by lunar regolith built up over time? The corner of a cubical object protruding from the ground would be missed by a machine trained to search for cubes. These many difficulties make the whole idea altogether less appealing. Until a general purpose artificial intelligence or serious effort of crowd-sourced volunteers can be employed on such a task, the completeness of the search will remain low. This should not be upsetting though, because as long as the search is incomplete there is still some chance for a positive detection. Who can say, perhaps Clarke and Kubrick will be vindicated some time within this century! (As a humorous aside, it was recounted by Clarke how the astronauts of Apollo 8 were tempted to radio back that they had seen an enigmatic black structure on the surface from orbit, but they decided that it would be in poor taste.)  Nonetheless, it is clear that the search is on for evidence of alien artifacts within the solar system, a search that is certainly nowhere near over.

Author: Alan

Hi, I'm a first year graduate student in the Penn State Department of Astronomy and Astrophysics and the Center for Exoplanets and Habitable Worlds.