An obsession with Earth-like conditions is blinding astronomers to other potential locations where alien life could flourish, one controversial theoretical physicist has argued, suggesting scientists are too inflexible to recognize all the possibilities. While the hunt for extraterrestrial life has so far focused on rocky planets that occupy roughly the same "sweet spot" in terms of where they orbit a star, MIT's Sara Seager says that ignores the possibility of liquid water and other essentials on exo-planets with orbits ten times further out than Earth is from our sun, National Geographic reports.
Although planets at such orbits would not, traditionally, be considered strong candidates for showing evidence of alien life, that's avoiding the core physics and chemistry, Seager points out. For instance, greater quantities of hydrogen gas in the atmosphere would have a more significant warming effect despite the cooler heat from a more distant star, she suggests in a paper in Science.
Conversely, planets generally thought of as too close to a star might be equally viable candidates, if they were dry enough to avoid the greenhouse effect from larger quantities of atmospheric moisture. Even a planet without a star altogether could still sustain life if it had its own source of heat, the physicist insists, such as if it had a radioactive core and enough of an insulating atmosphere to prevent undue loss of that warmth.
NASA has been using the Kepler space telescope to identify which planets might support life, using some fundamental guidelines including position in orbit and size. Last month, for instance, the space agency announced it had spotted three such examples, each within the so-called "habitable zone."
If Seager's arguments are accommodated within mission guidelines, however, Kepler's hunt could become far more comprehensive, though it's unclear whether the space telescope has the right combination of strengths to actually identify such planets. Currently, it is difficult to track the "biosignature gasses" - such as atmospheric oxygen in the case of Earth, or ozone and methane on exo-planets - of distant planets.
That could change within the decade, however, with NASA green-lighting 2017 plans for TESS, the Transiting Exoplanet Survey Satellite. It is expected to hunt for relatively nearby exo-planets, though it will take the combined efforts of TESS and the James Webb Space Telescope - itself set to launch in 2018 - before atmospheric analysis can take place.