Artifacts in the Solar System

One way that astronomers and astrobiologists search for life in the galaxy is observation of rocky planets orbiting other stars. Such planets may contain an atmosphere, liquid water, and other ingredients that are required for biological life on Earth. Once a number of these potentially inhabited planets have been identified, the next logical step in exploration is to send remote exploratory probes to make direct observations of these planets. Present-day study of other planetary systems is so far limited to remote observation with telescopes, but future plans for exploration include the design and deployment of small robotic exploratory spacecraft toward other star systems.

If intelligent, technological extraterrestrial life exists in the galaxy, then it is conceivable that such a civilization might embark on a similar exploration strategy. Extraterrestrial intelligent (ETI) civilizations may choose to pursue astronomy and search for planets orbiting other star systems and may also choose to follow-up on some of these targets by deploying their own remote exploratory spacecraft. If nearby ETI have observed the Solar System and decided to pursue further exploration, then evidence of ETI technology may be present in the form of such exploratory probes. We refer to this ETI technology as “non-terrestrial artifacts”, in part to distinguish these plausible exploratory spacecraft from the flying saucers of science fiction.

In a recent paper titled “On the likelihood of non-terrestrial artifacts in the Solar System”, published in the journal Acta Astronautica, myself and co-author Ravi Kopparapu discuss the likelihood that human exploration of the Solar System would have uncovered any non-terrestrial artifacts. Exploratory probes destined for another star system are likely to be relatively small (less than ten meters in diameter), so any non-terrestrial artifacts present in the Solar System have probably remained undetected. The surface and atmosphere of Earth are probably the most comprehensively searched volumes in the Solar System and can probably be considered absent of non-terrestrial artifacts. Likewise, the surface of the moon and portions of Mars have been searched at a sufficient resolution to have uncovered any non-terrestrial artifacts that could have been present. However, the deep oceans of Earth and the subsurface of the Moon are largely unexplored territory, while regions such as the asteroid belt, the Kuiper belt, and stable orbits around other Solar System planets could also contain non-terrestrial artifacts that have so far escaped human observation. Because of this plenitude of nearby unexplored territory, it would be premature to conclude that the Solar System is absent of non-terrestrial artifacts.

Although the chances of finding non-terrestrial artifacts might be low, the discovery of ETI technology, even if broken and non-functioning, would provide evidence that ETI exist elsewhere in the galaxy and have a profound impact on humankind. We do not argue that the search for non-terrestrial technology should be given priority over other astronomical missions; however, as human exploration into the Solar System continues, we may as well keep our eyes open for ETI technology, just in case.

Sky & Telescope article: Where have all the aliens gone?

If intelligent life is common in the galaxy, then the fact that we have not yet observed any extraterrestrials raises the question: where are they? The upcoming March issue of Sky & Telescope magazine features an article written by myself and Seth Baum where we discuss how the conspicuous absence of extraterrestrials may relate to the problem of sustainable development on Earth.

Funny story, we were initially slated for the January issue (we even made the table of contents), but a printing error lost the last 10 pages which sadly included our article. Nevertheless, the Sky & Telescope staff are excellent people to work with and made a fast turnaround. Be sure to check out the March issue!

Where have all the aliens gone?

The Milky Way is old enough that a slightly more advanced civilization than us could conceivably have colonized the galaxy several times over by now. Known as the Fermi Paradox, the absence of extraterrestrial observations is often taken to imply either the rarity of life or the impossibility of interstellar travel.

In a paper published in the February issue of the Journal of the British Interplanetary Society titled “The Sustainability Solution to the Fermi Paradox“, we challenge this conclusion with the possibility that exponential growth is an unsustainable development. That is, even if an extraterrestrial civilization has colonized the galaxy, it would have done so through rapid unsustainable growth and collapsed upon reaching a physical resource limit. Not enough time has yet passed for a sustainable growth civilization to colonize the galaxy, so there is still promise in the search for extraterrestrial life. Furthermore, though the absence of extraterrestrial civilization does not imply the unsustainability of exponential growth, it does increase the probability that humanity should transition to sustainable development in order to prevent its collapse. A more detailed writeup is available on the Lifeboat Foundation blog.

In other news, NASA’s Kepler Mission successfully launched yesterday evening! Over the next three years, Kepler will observe 100,000 stars in a patch of the Milky Way in search of Earth sized planets. This is the first mission with the capability of detecting Earth at a distance, so with any luck we’ll soon have a better idea of just how common small rocky planets are in the galaxy.