Like astrobiology, SETI is a multi-disciplinary effort, one that pulls together our knowledge and speculation about everything from life's origins to the development of planetary systems and the evolution of civilizations. It's remarkable to remember that it was only fifty years ago that Frank Drake launched the enterprise by scanning a 400 kHz window for interstellar radio transmissions. Epsilon Eridani and Tau Ceti, his target stars, gave us no evidence of extraterrestrial life, but we're continuing to refine the tools for detection. The Allen Telescope Array is just one example of the radio telescope equipment being brought to bear. The Low Frequency Array (LOFAR) and the Square Kilometer Array (SKA) will offer new SETI options in a wide range of wavelengths. SKA will cover 70 MHz to 10 GHz, later extending up to 30 GHz, while LOFAR will survey the skies from 10 to 240 MHz. LOFAR is currently being built and will be the most sensitive radio observatory in the world until SKA comes...

Gliese 581 d seems to be emerging as the exoplanet to talk about in terms of possible life, at least for now. You'll recall that the initial furor was all about Gl 581 c, but that world now looks to be more Venus-like than anything else, while Gl 581 d may just skirt the outer region of the habitable zone in this interesting system. Thus Dirk Schulze-Makuch's contention at the recent astrobiology conference in Houston that this 'super Earth,' if it holds life, may have creatures on it that have adapted to the gravity of a planet at least seven times as massive as the Earth. That would probably produce a population that tends to crawl rather than fly, said the Washington State researcher, and we can let our imaginations go to work on the possibilities. As to Gl 581 d itself, its orbit around this red dwarf may place it in the same relative position that Mars is to our Sun, but throw in volcanoes, a magnetic shield and a thick atmosphere with water oceans below and you could have the...

Finding life on a world in the outer Solar System -- think Enceladus or Titan for starters -- would be an extraordinary step forward. Martian microbes, if they exist, might be evidence of contamination, or we might be evidence of ancient contamination from Mars, given the ready exchange of materials between our planets in the last several billion years. But the outer system offers the possibility of discovering life that originated entirely separately from anything we know. The problem is that we're a long way from having built the spacecraft that can make these detections. That's why places like Pitch Lake, on the island of Trinidad, are so useful. Other than the temperature, conditions here are about as close to what we might find on Titan as anything we know. The 114-acre lake is a cauldron of hot asphalt permeated with hydrocarbon gases and carbon dioxide. As you can see in the image below, it's hardly a hospitable-looking place. But this asphalt hell-hole defies expectation. As...

The Stephen Hawking controversy continues to bubble, with discussion on the Larry King show and the appearance of David Brin's essay The Other Kind of Aliens. It's all to the good to get such discussions widely circulated, even if it can be dismaying to find that so many respondents believe the answers about how alien cultures will behave are obvious and can be readily deduced from our own cultural experiences. But maybe that's because this is a new controversy, one that the search for exoplanets is only now bringing to a wider public in any serious way. There is plenty to ponder, and while we debate the nature of alien culture, let's look at something more immediate. The Protocols of SETI Success SETI continues to look for signals of extraterrestrial civilizations. What happens if a signal is actually detected? For the answer, we can look to the SETI Post-Detection Taskgroup, created by the SETI Permanent Study Group of the IAA (International Academy of Astronautics). The...

These are exciting times for planet hunters, with Kepler and CoRoT in the hunt, three ongoing searches for rocky worlds around Centauri A and B, and the continuing WISE mission, which may identify planet-bearing red and brown dwarfs that we haven't spotted yet, not to mention numerous radial-velocity, transit and microlensing projects. But stepping back to get the big picture is a bit sobering. Jean Schneider did that recently in a paper looking at the far future of direct imaging, wondering where we were headed after Kepler and CoRoT. Schneider (Paris Observatory) talks about a 'conceptual or knowledge horizon,' one we've discussed earlier, that limits us to detecting biomarkers and keeps us from going much further than that for centuries. Seeing Alien Life Up Close Why? A short article on Schneider's work in Astrobiology Magazine condenses the paper's argument. Suppose we do discover signs of life on a planet in the habitable zone of a nearby star. Huge space arrays could help...

NASA's teleconference from the Astrobiology Science Conference 2010 in Houston offered some interesting news about the discovery of microscopic fossils in gypsum from a period about six million years ago, when the Mediterranean Sea had all but dried up. Gypsum (calcium sulfate) precipitates out of sea water, and the find has implications for finding life on Mars, as I'll explain in a moment. What gave me a chuckle, though, was that after a discussion between four crack astrobiologists about life's appearance on Earth and the best ways to search for it elsewhere, the first question from reporters was about Stephen Hawking's views on aliens, and whether NASA had a policy on broadcasts to the stars. The answer is clearly no, and NASA's Mary Voytek noted the differences of opinion between the agency's scientists on the issue, prompting Steven Squyres (of Mars rover fame) to note that our signals are already in play in the form of TV broadcasts and planetary radar signals. I'm thinking...