Why Exomoons Are Way Cooler Than Exoplanets
Last edited Sat Jan 12, 2013, 07:56 PM - Edit history (1)
Take a Jupiter and plop it into a Mars-like orbit and it's moons would begin to heat up. In fact, they might heat up more than you might expect. The gravitational tidal forces of Jupiter also contribute to the heating. The ten miles of ice that cover Europa melt and you are left with a warm ocean moon with more water than Earth. Rivers from giant salt water oceans seventy miles below the surface began to bubble up and flow across Callisto and Ganymede. Is this a result of some unusual characteristic of Jupiter? No! if we move Saturn closer to the Sun, it's moon Titan might have to be renamed to mini-Earth and salt water rivers filled with organic compounds would begin to flow on Enceladus.
However, there's a problem. Jupiter's and Saturn's moons might not be large enough to sustain an atmosphere's capable of sustaining life so let's try a planet six times the size of Jupiter. Jupiter has 60 moons so according to what we know about planet size and number of moons, this planet might have as many as 400 moons and perhaps 20 Earth-sized moons with water. Suppose intelligent life evolves on one of those moons. It would be a scientist's dream come true. There would be four-hundred nearby moons to explore and many would be inhabitable.
All the inhabitants of such a moon would enjoy many advantages over Earthlings. Screw up your home world up with pollution or war, and you might get a second, third perhaps as many as twenty chances to get things right. The information an alien intellgence would gain by exploring 400 nearby moons would give these aliens big advantages in terms of their understanding of biology, geology and the hard sciences. For example, telescopes on airless worlds would be easy. Biologists would gain knowledge by understanding how life develops on multiple worlds. No one would argue whether travelling into space was worth it.
How common an occurrence could this be in our galaxy? Compared with Earth-sized planets, large gas planets are rarer but also a lot more stable. For example, gas giants would have no trouble existing around the small star systems that dominate our galaxy. In contrast, Earth-sized planets orbiting small stars in order to get enough heat have to enter orbits very close to their sun. This causes problems including sun's tidal forces causing volcanism, and orbital and rotational instabilities. These are not problems for big planets or their moons. Planets more than ten times the size of Jupiter have already been catalogued.
The Kepler NASA mission that looks for exoplanets has identified 35 habitable moon candidates. Although the computational power is intense, Keppler data can be used to detect exomoons.
Given all the advantages that intelligent life has on exomoons, one wonders how such aliens might view Earthlings. Perhaps Earthlings are the social lepers of the Universe and that's why alien contact always seems to come in the form of communications with strange people or in the form of something that seems a lot like a secret government project.
UPDATE: A couple of devil's advocates argued that such moons would be unstable or unlikely so it's worth mentioning that science disagrees with their points of view as was noted in the article links As noted scientists have identified 35 gas giants with potentially habitable moons and spent the scientific effort in developing a complex means for detecting the existence of such moons using Keppler data. The Group Planet Hunters is actively searching for such moons and gas giants. Also, a theoretical model has been developed that specifically suggests that points out that the sorts of moons suggested are stable long term just like the one's in our solar system are. Second, the major impact hypothesis has been used to nay say just about any possibility for potential life outside the solar system but the lecture by SETI and Keppler professor in the video listed above doesn't believe that argument holds any water because it's merely unbridled speculation. She argues that it's easier to argue that Jupiter's presence causes asteroid belts to develop which creates problems for Earth-like planets but SHIELDS THEIR MOONS from such problems by absorbing such unstable planetary objects. As with any planet-moon system some moons initially get sucked back into the planet. However, others that are further away develop stable orbits. As noted in the above theoretical model link, larger planets tends to have more moons so higher gravity doesn't mean fewer moons as a result of the gravity sucking the moons into the giant planet.
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