Today's sessions at the [email protected] conference stretched the mind as these multidisciplinary gatherings usually do. Chris Impey from the University of Arizona set the stage by summarizing the state of the known Universe in terms of life. So much has changed in the last decade, and all in the direction of suggesting a Universe more habitable and friendly to life. "From blue whales to blue bottles, from orchids to orcas" as Impey put it, life on Earth is superficially varied but in fact deeply related. Is our situation unique?
From the point of view of habitats for life, all the news is good. There are planets aplenty, with the rate of discovery increasing, more than 30 planets known with 1-10 Earth masses, 50 systems with more than one planet. The old notion of the Goldilocks principle -- Earth being uniquely far from the Sun to be Just Right -- has been smashed. Europa, Enceladus, Titan, Mars, deep layers in gas giants all present potential habitats. If that is typical, then there are worlds unnumbered where life might arise. (Don't hold your breath to find out though. NASA currently has no Europa missions planned. In fact the whole solar system may see a significant downturn in visiting spacecraft because of lack of funds on Earth)
Even regions of the galaxy thought to be uninhabitable need rethinking. Stars in globular clusters orbiting in the galactic halo, were long thought to be too deficient in heavy elements to form planets, "Not enough grit to form the pearl". Yet that was all changed by the discovery of a "Methuselah" planet that somehow was ejected from the galactic disk and ended up in orbit around a star in a globular cluster.
Life may not even need a star. Planets wandering the galaxy free of any star may also be quite plentiful. If they have radioactive cores, there is no reason why life could not live off those heat sources. Most of the Earth's biomass is tens and hundreds of meters below the surface, outweighing the creatures on the surface. Their survival does not depend on sunlight but on geothermal heat. A conservative estimate of the number of habitable planets in the Universe might be a billion billion.
And we have deployed a whole armada of spacecraft and instruments that use various techniques to find even more planets, including the astonishing feat of imaging them directly (they are so small, dim, and close to the parent star that isolating their image still requires great technical virtuosity. )
Some of the new planets that may be found are as close as 16 light years, some as far as 6000. These most distant ones will be imaged by gravitational lensing, where observations are made by spacecraft at the focal point of light rays from distant stars being bent by passing close to the disk of our Sun.
So all the first 3 factors in the Drake Equation regarding the number of habitable worlds are now known quantities, a huge step forward.
But will "simple" life evolve to intelligence? Astrobiologist Lynn Rothschild from NASA's Ames Research Center reminds us that there is no such thing as simple life -- even the simplest bacterium is incredibly complex. How that complexity evolved is still a mystery.
Of course life on any planet has to survive numerous hazards in order to have time to evolve. Asteroid impacts, giant solar flares, even gamma ray bursts could annihilate life. Astronomer Robert Rood of the University of Virginia suggested adding the term F sub J (frequency of Jupiters) to the Drake Equation. Jupiter's gravity draws in many comets and asteroids that might otherwise strike the smaller planets. Without Jupiter to take the hit for us, species extinction level impacts would happen every hundred thousand years, instead of every 100 million.
The molecules of life seem to form easily and plentifully. Chemist Susanna Widicus Weaver of Emory University reported that there are now 160 molecules that have been identified in the interstellar medium and in comets, including molecules up to 13 atoms strong.
The galactic table seems set for life. Whether we will forever dine alone is still unknown.
Planetary Society Advisor Jon Lomberg is an artist who has worked on many SETI-related projects, including the film of Carl Sagan's CONTACT and NASA's legendary Voyager Record.
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