Earth's Twin Discovered?-A Contrarian View
Close to 
claiming that there is no Santa Claus, Jay Manifold of the A Voyage to Arcturus blog believes that the intense media hype around the possibility of life on "Earth's Twin," exoplanet Gliese 581c, is spin created to help secure funding for NASA's Terrestrial Planet Finder.
The blog describes the discovery as a "hot Neptune" that has spiraled close enough to its star to have a "surface" temperature in the range that could support liquid water. But Gliese 581 C is dramatically un-Earthlike.
The NASA Terrestrial Planet Finder observatories will study all aspects of planets outside our solar system: from their formation and development in disks of dust and gas around newly forming stars to their suitability as abodes for life.
What Gliese 581c "lacks is a history remotely resembling Earth's. To quote Timothy Ferris (page 338 in the paperback edition of Coming of Age in the Milky Way), things are as they are because they were as they were. Earth swarms with life, including life recently capable of investigating other solar systems, because it has maintained - with considerable assistance from Jupiter, the Moon, tectonic plate movement, and other influences - a very rough homeostasis for billions of years, punctuated with just enough change, including extinction events of sufficient (but not oversufficient) severity, to drive the development of immense biological variety.
"Gliese 581 C has none of this - and equally important, and entirely lost in the employment of this discovery in the "are we alone?" narrative, is that it has its own history, one certainly as astonishing as our own, irrespective of whether it has led to intelligent aliens, or even bacteria."
A useful caution. The fact is, we don't know much about 581c. Speculation is fun, but not worth arguing over. My one variance: I suspect that life is not so highly contingent as we think, that it is present in far more forms and places than we imagine. I rather think we will find it not only on Titan, but on Jupiter and Saturn as well. This, I hasten to say, is what I suspect, not what I can prove.
JacK...Agree with your thoughts on discovering microbial life on Titan, Europa, etc. Finding "animal" life is aonther story...but I do think that a Gliese 581c type will be found supporting ETI life at some point in the next 50 years. Casey.
Posted by: Jack Butler | May 03, 2007 at 11:09 AM
We barely know anything about Gliese581c's "present" (the way it was roughly 20 years ago). I'm highly skeptical of anybody who claims to know much about its past. For example, the claim that "it has no Jupiter". The fact that we have only discovered 3 planets so far (and 2 of those within the past month, mind you) should not be taken as any sort of proof that no other planets exist in the system. And while Gliese581d is not so massive as Jupiter, it is larger than 581c, and I think it's a bit closer to 581c than Jupiter is to Earth. I suppose we could say his speculation is no less valid than anybody else's, but it's still pure speculation at this point.
Also, it's been discussed at length that the measured temperature is *not* the surface temperature, which we can't know until we know more about the planet's atmosphere.
Posted by: Wolfger | May 03, 2007 at 03:04 PM