(Astrobiology) Why the Universe May Teem With Life

For years, both those who subscribe to an "abundant life" theory have argued against the dominant scientific thought that only worlds within a very narrow criteria could support life. As our knowledge of the universe around us expands, prevailing wisdom may be turning in favor of those supporting "abundant life" theories.

...it's becoming increasingly clear that the question of what makes a planet habitable is not as simple as finding it in just the right spot. Many other factors, including a planet's mass, atmosphere, composition and the way it orbits its nearest star, can all influence whether it can sustain liquid water, an essential ingredient for life as we know it. As astronomers explore newly discovered planets and create computer simulations of virtual worlds, they are discovering that water, and life, might exist on all manner of weird worlds where conditions are very different from those on Earth. And that means there could be vastly more habitable planets out there than we thought possible.

As a planet orbits a star, particularly those with close or eccentric orbits, the planet is at times squeezed or stretched by their star's gravity, generating an effect known as tidal heating. In a study on tidal heating at the University of Arizona Tuscon, researchers found...

...given a large enough variation in gravitational pull around the orbit, this additional heat from below could be enough to thaw out frozen planets orbiting a red dwarf, despite the feeble radiation they receive from their host stars. The extra heat could also stimulate volcanic activity, even on planets with a low mass, potentially giving them thicker atmospheres and the stronger greenhouse effect needed to maintain liquid water beyond the Goldilocks zone.

When looking for planets that may harbor life, searchers may want to throw out hability/inhability of the planet as a whole, and consider to what degree a planet may be habitable. David Spiegel of Princeton argues...

It makes more sense to think in terms of "fractional habitability", (Spiegel) says, as in what fraction of a planet's surface is habitable, for what fraction of the year, or for what fraction of its history. "Even the Earth is not 100 per cent habitable, at least by the standard liquid-water definition," Spiegel points out. "Parts of the planet are frozen part of the time. Parts of the planet are frozen all of the time."

Though our definitions of what makes a planet hospitable for life may be expanding, and potentially expanding our list of candidate worlds for finding life, perhaps we should not get our hopes up too much. Says Johnathan Lunine of the University of Arizona...

don't think we really understand how or why the Earth has been habitable in its history and what the excursions from habitability really were...and until we do, it's hard to be anything but sceptical that some of these models are really going to inform the search."

SOURCE

[edit on 20-11-2008 by SaviorComplex]

[edit on 20-11-2008 by SaviorComplex]