What is life REALLY like on Kepler-22b?
A story about the newly discovered Kepler-22b appeared in my Google science news feed. Kepler-22b, as described by Wikipedia, "... is the first confirmed extrasolar planet found by NASA's Kepler Space Telescope to orbit within the habitable zone of a Sun-like star."
The story was a guest essay by Wade Sarkis, to the online magazine MPNnow.com. I clicked over to this story thinking I'd read some real science about what it would be like to live on Kepler-22b. What I found instead was an orgasmic Utopian political fantasy by a writer with stars in his eyes. The only fact quoted was the distance to Kepler - 600 Light Years. Needless to say, I didn't learn anything I didn't already know.
So let me tell you what little I know about Kepler-22b.
We know, approximately, what the diameter of Kepler-22b is because of how much light is occluded when it passes in front of its star. It is about 2.4 times the radius of Earth.
From that small bit of information, we can calculate Kepler-22b's probable gravity, depending on it's probable makeup. We would do so by noting that the gravity of a planet (g) is found with this formula: g=G(m/(r^2)).
For instance, if the planet consists of the same sorts of materials that make up the Earth, (rocky metals and water) then a person who weighs 200 pounds on Earth would weigh 485 pounds on Kepler-22b. Not a nice place to vacation for us humans!
But maybe we would luck out, and Kepler-22b would be less dense. This is possible if it were made of water. If Kepler-22b were made entirely of water it would only be 2.5 times as massive as Earth, but the gravity would be a pittance. A 200 pound person would weight only 86 pounds on a watery Kepler-22b - from the deck of his ship, since there would be no land. But it would be a strange ship, since there would also be very little if any atmosphere. The gravity of this water world would be too low to keep most of the atmosphere from escaping! And without atmosphere, even the water vapor would try to escape the bounds of the planet. Perhaps it would hang around if frozen solid, sort of like Jupiter's moon Ganymede.
So what would be comfortable to a human? If Kepler-22b were only 6 times as massive as Earth the gravity would be similar to Earth. You would weight just about the same. But this density would suggest a planet poor in metals, made mostly of silica and water. Granite and sandstone would exist, but heavier minerals would not. The term "Bronze Age" would be a complete mystery to the inhabitants of Kepler-22b, to whom the fused glass spear point would be the height of their technology.
Is there life on Kepler-22b? Who knows? But if they are able to develop human-like technology, if they can mine the metals to make a radio, and if we ever detect a signal, then we will know that theirs is a much heavier world than ours.
For those who are curious, I made a spreadsheet that calculates the gravity of planets found by the Kepler space observatory. Click on that link to calculate the the possible gravity on the surface of the planets found by the NASA's Discovery Program.