The Terrestrial Planet Finder and SETI

There are other ways to find alien civilizations, ones that could be considered better in some ways. Some time ago, NASA released plans for The Terrestrial Planet Finder, an orbital telescope platform that is still under design that will be launched in about 10 years. The TPF’s purpose will be to cancel out the glare of stars and look right at the local planets, rather than looking for signs of them. Upon locating one, it will analyze the spectrum of light coming from it and figure out what elements and materials are in the atmosphere and on the surface, taking advantage of the fact no no element or material absorbs and emits the same spectrum of infrared, visible or ultraviolet light.

Possessing the ability to locate and analyze alien planets of almost any size for quite a distance from Earth, The TPF could be used to identify worlds that are inhabited by, or at least have had work done on them by aliens. The presence of an intelligent race on a vaguely Earth-like planet may have effects on its atmosphere and surface at some point in time, some worlds may have even been totally changed by one (such as us terraforming Mars or Ganymede). These signs could be picked up by The TPF.

Let’s start by looking at how we could identify a civilization around our age, give or take 200 years or so. After we began the Industrial Revolution, we began to release a great deal of pollutants, some are normal to Earth, like carbon dioxide, others are not so normal. Take our activities this century for example, we began to produce chlorofluorocarbons (CFCs) for various purposes in high enough concentrations to disrupt our atmosphere. CFCs are synthetic, so detection of them in an atmosphere is a dead ringer for the presence of a sentient species. Air pollution can take other forms as well, though some are not necessarily caused by sentient activity, but do promote the idea. Such signs are high levels of smog and surface ozone. Ozone depletion could be a sign if it seems inconsistent with anything the planet seems to have experienced.

Since the TPF will analyze all light coming from the planet, certain if not many surface materials may be surmised. Materials it will actively search for include water and vegetation, possibly others. If the species on planet urbanizes an area heavily enough, the materials may show up. If the materials are natural, they may still indicate intelligence if the region appears to grow over time.

So, it may be possible to detect a society based on anomalies on their homeworld. It may have more success however looking to the other worlds in a star system for more obvious things. Let’s say it spies a planet which should not have an atmosphere, but does. This may suggest the beginnings of a terraforming project. Or more dramatically, what if a world shows signs of a completed terraforming project such as spectral signatures of PFCs, SF6 and other such synthetic gases. The TPF, or another similar device could find societies by finding worlds that are not as they should be, or show distinct signs of synthetics.

This method of looking for life would dramatically increase our chances of finding someone. Since there is likely to be only a relatively short time between a species’ advent of strong radio and the strict use of tight radio beams, our chances of detecting ordinary transmissions are not good. It is also inefficient to send powerful, purposeful messages out in every direction. So, unless they are aiming tight beams right at the Earth, there is not much chance there are purposeful messages waiting for us. Also, we cannot discount the possibility that nearby species may have a rule or law about contacting societies at our level, kind of like The Prime Directive of Star Trek. Radio is probably not the best way to look for people.

Searching for signs of their activity, however, has a very good chance of success. It is doubtful that a society will move right from Pre-Industrial technology right to clean high tech, so there is good chance of finding pollutants. And a space faring civilization may at least build lots of domes on other planetary surfaces, those could be picked up by their distinct content of breathing gases and possibly vegetation.

Radio shouldn’t be ruled out completely though. Identifying habitable planets could focus the SETI effort, focus very sensitive receptors right on the planet. Or go a step further, transmit our own powerful radio beam to a world we think may be inhabited. The point is, searching by spectral signatures from planets will definitely increase our chances of finding NTIs (Non-Terrestrial Intelligences).