If extraterrestrials were to set up a colony in our Solar System, where would they choose to settle? Gregory Matloff and Anthony R. Martin make the case for the Kuiper Belt in a recent paper for the Journal of the British Interplanetary Society. Kuiper Belt Objects (KBOs) are, after all, easy to exploit as a resource base without the burden of a planet’s gravity well. They are rich in volatile materials (more so than main belt asteroids), close enough to the Sun to harvest solar power, and far enough out that visits by those of us living in the inner Solar System would be few and far between.
Moreover, the orbits of KBOs are relatively unaffected by planetary perturbations. Matloff was intrigued enough by these factors to make a proposed infrared search of the Kuiper Belt the subject of a 2004 paper (“A Proposed Infrared Search for Artificial Kuiper Belt Objects,” JBIS 57, pp. 283-287). His new paper follows this up with an examination of the characteristics that artificial KBOs ought to display, comparing these to known objects.
How big would such an artificial habitat be? The earlier paper assumed a radius of five kilometers, on the same order of magnitude as some O’Neill designs that would house 10,000 people and more, but the authors of this new study factor in size variations up to 50 kilometers and weigh the effects of varying degrees of reflectivity. Certain assumptions are unavoidable: Matloff and Martin assume, for example, that the temperature of an artificial KBO is within the range 273-373 K, the temperature range of liquid water.
The authors find that the K-band astronomical photometric filter is sensitive to radiation temperature variations in their hypothetical artifical KBO (this is a significant result, for Earth’s atmosphere is relatively transparent in this spectral band). They also discuss visible bands of infrared in which artificial objects should be distinguishable from real KBOs. The authors then run their criteria against NASA’s Planetary Data System. A small number of real objects have characteristics similar to those predicted for artificial bodies.
This work thus results in an initial selection of targets for an advanced infrared search for artificial objects, using these criteria:
The authors examine the facilities available for infrared observation, from large ground-based telescopes using adaptive optics (think ESO’s Very Large Telescope in Chile, or the twin Keck telescopes on Mauna Kea in Hawaii) to the Hubble Space Telescope, the Infrared Space Observatory and the Spitzer Space Telescope. “The intriguing situation exists that only a few real KBOs have photometric characteristics similar to those predicted for artificial bodies, but infrared observations of KBOs are limited,” Matloff and Martin write.
Their paper concludes with a series of suggestions for improving such observational data, including studies in the K-band and coordinated use of Hubble and Spitzer to obtain full infrared data on the targeted KBOs. The paper is Gregory L. Matloff and Anthony R. Martin, “Suggested Targets for an Infrared Search for Artificial Kuiper Belt Objects,” JBIS 58 (January/February 2005), pp. 51-61.