One school of thought in cosmology insists that Earth is not unusual, there must be billions of Earths in the galaxy. Planets much larger than Earth orbiting within the “habitable zone” around a star—that is, they could possibly support life as we know it—have been dubbed “super-Earths,” but they are known to be super in size only, nothing else.
Yesterday, we noted the difference the moon makes to Earth’s habitability. An unusually blunt item at ScienceDaily now tells us, “’Super-Earths’ may be dead worlds: Being in habitable zone is not enough”:
The results suggest that for some of the recently discovered super-Earths, such as Kepler-62e and -62f, being in the habitable zone is not enough to make them habitats.
Dr. Lammer comments “Our results suggest that worlds like these two super-Earths may have captured the equivalent of between 100 and 1000 times the hydrogen in the Earth’s oceans, but may only lose a few percent of it over their lifetime. With such thick atmospheres, the pressure on the surfaces will be huge, making it almost impossible for life to exist.”
The ongoing discovery of low (average) density super-Earths supports the results of the study. Scientists will need to look even harder to find places where life could be found, setting a challenge for astronomers using the giant telescopes that will come into use in the next decade.
The basic problem seems to be that a planet, even in the habitable zone, can mostly be a gasball with a thick, very high pressure atmosphere that would inhibit life as we know it.
Granted, we have had problems recently coming up with a definition of life. But the definition, if it succeeded, was meant to unify categories of entities that we already agree are alive. Jury’s out on whether nothing or something completely different from that could inhabit these Keplers. Nothing that we now recognize as life would likely live there.
See also: “Behold, countless Earths sail the galaxies … that is, if you would only believe …”
Don’t let Mars fool you. Those exoplanets teem with life!
But surely we can’t conjure an entire advanced civilization?
How do we grapple with the idea that ET might not be out there?