We've already speculated here that if the Kepler mission finds few Earth-like planets in the course of its investigations, the belief that life is rare will grow. But let's be optimists and speculate on the reverse: What if Kepler pulls in dozens, even hundreds, of Earth-sized planets in the habitable zones of their respective stars? In that case, the effort to push on to study the atmospheres of such planets would receive a major boost, aiding the drive to launch a terrestrial planet hunter with serious spectroscopic capabilities some time in the next decade. Budget problems? Let's fold Darwin and whatever Terrestrial Planet Finder design wins approval into the same package, and make this a joint NASA/ESA mission. Finding numerous Earth-like planets will be a driver, as will gradual economic recovery. Finding Many Earths The discovery of numerous 'Earths' would also galvanize public interest in interstellar flight, which offers a useful educational opportunity. Even the short-lived...

If we're looking for pristine environments for life, Antarctica offers much. More than 150 subglacial lakes have been discovered beneath the ice sheet, isolated from the surface for long periods and possibly home to species that have never before been observed. From November 2007 to February 2008, a subglacial lake named Lake Ellsworth was studied by a four-person team that used seismic and radar surveys to map the lake's depth and take other measurements that made clear its potential for exploration. Their blog is archived here, and it makes for good reading. Image: A DeHavilland Dash-7 flying near the British Antarctic Survey research station at Rothera. The station is 1630 kilometers southeast of Punta Arenas, Chile, and served as a staging area for the Lake Ellsworth studies of 2007-2008. Credit: Natural Environment Research Council. Europa, anyone? Well, there are certain resemblances. If the thickness of the ice on Europa is still controversial, we know for a fact that Lake...

A Europan Scenario Between living dirigibles on gas giants and potential organisms under the ice, we've had quite a week in terms of exotic life-forms. I didn't have space in yesterday's review of Unmasking Europa to talk about the book's chapter on biology, but here's an interesting glimpse of a not implausible biosphere on that moon, as presented by physicist Richard Greenberg: Brisk tidal water sweeps over creatures clawed into the ice, bearing a fleet of jellyfish and other floaters to the source of their nourishment. As the water reaches the limits of its flow, it picks oxygen up from the pores of the ice, oxygen formed by the breakdown of frozen H2O and by tiny plants that breath it out as they extract energy from the sun. The floating creatures absorb the ocygen and graze on the plants for a few hours. The water cools quickly, but before more than a thin layer can freeze, the ebbing tide drags the animals deep down through cracks in the ice to the warmer ocean below. Most of...

By Larry Klaes 'The Gasbags of Jupiter' sounds for all the world like the title of an early 1930s novel that would have run in a venue like Science Wonder Stories. In fact, as Larry Klaes tells us below, the idea grew out of Carl Sagan's speculations about free-floating life-forms that might populate the atmospheres of gas giant planets like Jupiter. Cornell physicist Edwin Salpeter had much to do with the evolution of that concept, helping Sagan produce a paper that was a classic of informed imagination (and one that led to numerous science fiction treatments as the idea gained currency). Larry's celebration of Salpeter's life gives a nod to that paper but also notes his deep involvement in the study of the most distant celestial objects. On March 14, the Department of Astronomy at Cornell University will commemorate the life of one of their most prestigious faculty members: Edwin E. Salpeter, the James Gilbert White Distinguished Professor of Physical Sciences Emeritus. Salpeter...

Just how many forms of life are there? We often speculate here about life on other worlds, but Paul Davies (Arizona State) is currently exploring the question from a different perspective entirely. Davies would like to know whether a 'second genesis' might have occurred, producing a fundamentally different form of life that would have evolved right here on Earth and might still occupy our planet. Life may, in other words, have started many times, perhaps with significantly different results we just haven't uncovered yet. Call it a 'shadow biosphere,' a concept the physicist calls for exploring: "...[It] is still just a theory. If someone discovers shadow life or weird life it will be the biggest sensation in biology since Darwin. We are simply saying, 'Why not let's take a look for it?' It doesn't cost much (compared to looking for weird life on Mars, say), and, it might be right under our noses." Finding these alternate life forms, if they exist, may be tricky, as they could be...