The day the first Viking lander touched down on Mars is still fresh in my memory, particularly the early confusion about the real color of the Martian sky (which had seemed, by data misinterpretation, to be a rich blue). Then the excitement about possible life through experiments combing through the top few inches of Martian soil. Bob Schieffer announced there may be life on Mars -- "no fooling", said Schieffer with a delighted grin -- on CBS news not long after, but later studies discounted the one experiment that might have detected biological activity. Gil Levin, the scientist in charge of the disputed Viking experiment, still thinks it was successful. But other experiments could find no organic molecules in the Martian soil, an assumed prerequisite for life. Now a new paper argues that the Viking methodology was flawed. In fact, similar experiments don't even find organic molecules in the Atacama Desert between Chile and Peru, where dry conditions seem conspicuously Mars like,...

From South Africa comes news of a striking find: bacteria living two miles beneath the surface and, more significantly, dependent only on the sulphur and hydrogen produced by geological processes rather than on the energy of the Sun. That life should form in such remote venues seems extraordinary, but the finding gives credence to the belief that similar microorganisms might have evolved on other worlds right here in our own Solar System. Sure, we've found life in some hostile places before, including ocean vents and petroleum reservoirs, but their biological processes can all be traced at least partially back to the Sun, which provided the energy source for photosynthesis and therefore produced the needed nutrients for life. This new find, uncovered in a rock fissure that intersects the Mponeng gold mine near Johannesburg, uses radioactive decay as its power source, converting water molecules into hydrogen and ultimately producing hydrogen sulphide out of sulphate molecules in the...

Many years back I wrote an article for Glenn Hauser's Review of International Broadcasting called "Where the Real DX Is." DX is the shortwave radio term for seeking out distant signals, a sport in which the smaller and fainter the station, the more interesting the catch. I was laboring with an old FRG-7 receiver to attempt impossible receptions like the Falkland Islands and Tristan da Cunha (neither of which I ever heard), but in the back of my mind were the nearby stars. What about receiving a signal from one of them? And while I wrote about the emerging SETI scene, my real thinking was that an extraterrestrial reception wouldn't be from a beacon -- I still doubt these exist -- but from accidental leakage from a technological society. Now a new paper by Harvard's Abraham Loeb and Matias Zaldarriaga suggests an interesting strategy for finding such leakage, via a a low-frequency radio telescope study that will look at highly redshifted 21 centimeter emissions from hydrogen. The...

Frank Drake's famous equation, first outlined at the Green Bank Conference in 1961, tries to estimate the number of civilizations in our galaxy with which communications might be possible. Such attempts are obviously speculative, but Drake concentrated on factors like the number of habitable planets, the fraction of those that contain life, and the fraction of those on which civilizations eventually appear. The equation in its entirety looks like this: Here, N is the number of civilizations with communications potential in the galaxy, with R* the rate of star formation, fp the fraction of stars with planets, ne the number of planets that can support life per system, fl the fraction of planets that develop life, fi the fraction that develop intelligent life, fc the fraction that go on to communicate and L the life time of a technological civilization. Zsolt Hetesi and Zsolt Regály (Eötvös University, Budapest) discuss the kind of civilizations that may emerge in a recent paper. As far...

Centauri Dreams admits to troubling new doubts about a variant of SETI called METI -- Messaging to Extraterrestrial Intelligence. The notion, also known as 'active SETI,' is backed by some members of the SETI community and is especially strong in Russia. Its premise is that rather than listening passively for signs of extraterrestrials, we should actively try to achieve contact through messages of our own. This would constitute a 'brightening' of our civilization in the radio sky, making us more noticeable by many orders of magnitude. A number of intentional signals besides the famous Arecibo message of 1974 have already been sent. The so-called 'Cosmic Call 1' message was transmitted from the Evpatoria Planetary Radar site in the Crimea in 1999, targeting four Sun-like stars and sending an overview of terrestrial life written in a code called Lexicon. Cosmic Call 2, sent to five Sun-like stars, followed in 2003. Based on the target list and the distances involved, the window for a...

Galactic catastrophism -- the idea that certain kinds of cosmic events can destroy life on a periodic basis and prevent the emergence of technological civilizations -- comes in a number of variants. And some catastrophe theorists believe such events don't necessarily rule out species survival because their effects change over time. As we saw yesterday, Israeli theorist Itzhak Shechtman believes super-civilizations do arise despite the hazards of periodic extinctions, and argues that we may well find traces of their activities. I return to Shechtman today because his paper crystallizes this interesting debate, especially when we turn to gamma-ray bursts (GRBs) as the agent of catastrophe. Shechtman examines the work of James Annis, who speculated in 1999 that although gamma-ray bursts could be deadly, their rate of occurrence declines over time. If this is the case, the universe may move into a 'phase transition' when the time between GRBs comes to equal the time needed for the...

The Fermi Paradox ('Where are they?') is becoming something of a cottage industry; everyone has an answer. My own hunch is that while life is widespread, technological civilizations are not, with perhaps as few as 5 to 10 active at any given period in the galaxy. But many would disagree with this assessment, including Itzhak Shechtman. The Israeli theorist speculates that ancient super-civilizations may well be out there, and perhaps detectable through an upgraded SETI effort. But his first task, in a recent article in the Journal of the British Interplanetary Society, is to silence the critics. For cosmic catastrophe theory has gained traction in recent years. In its scenarios, certain cosmic events -- gamma-ray bursts, neutrino-induced extinctions, disastrous interactions with galactic spiral arms -- could cause species extinction that would prevent long-lasting cultures from ever developing. A solution to the Fermi Paradox? Nobody lives long enough to visit us. But Shechtman...

Can living microbes travel between the planets, blown off one by a colossal asteroid impact, for example, and carried in debris to another? Some have suggested that life on Earth originated on Mars in just this way, but interesting work by electrical engineer Tom Dehel now offers an alternative. Dehel, who is also working on a law degree at Rutgers, was studying the Earth's electromagnetic fields and their impact on GPS satellite systems for the FAA when he realized that bacteria could be ejected from Earth by the kind of fields that create auroras. The work, presented at a meeting of the Committee on Space Research (COSPAR) in Beijing, was the subject of a recent New Scientist story by David Chandler. And it's intriguing because whereas asteroid impacts of the needed size were relatively rare even in the early Solar System, the electromagnetic fields in question are common. Dehel sees the possibility of bacteria floating in the upper atmosphere and reproducing there, evolving ways...

Jose Garcia writes from the wonderful Meme Therapy, where he's conducting another brain parade, this one asking science fiction writers and scientists a straightforward question: "Do you think it likely that the first discovery of extraterrestrial life will be made by a rover?" The answers to all of Jose's brain parade questions are stimulating and reflect a wide variety of perspectives, from Robert Zubrin's unqualified "No. It will be made by human explorers operating on the surface of Mars," to writer Peter Watts' call for widening the search from planets to comets and molecular dust clouds. Centauri Dreams' guess is that extraterrestrial life may well exist deep within the Martian soil, but the first conclusive proof of life beyond Earth will come by rover and in a more exotic place, such as one of the Galilean moons of Jupiter or, if we want to get truly exotic, in the bizarre deep freeze of Titan. Because this is by nature guesswork, I'm just playing a hunch that Mars is going...

Centauri Dreams was amazed to realize that almost two years have passed since Christopher Rose and Gregory Wright posed a bold challenge to SETI researchers. In an article in the September 2 (2004) issue of Nature (a cover story, no less), the duo suggested that we are more likely to achieve extraterrestrial contact through artifacts -- organic material embedded in an asteroid or comet, say -- than through radio or optics. Larry Klaes, posting a link in a comment here on the Rose/Wright discussion, recently jogged my memory about this article, which deserves a renewed look. Rose (Rutgers University) is a professor of electrical and computer engineering; his work with wireless technologies convinced him that "...it's often MUCH (many many orders of magnitude) better from an energy use perspective (and perhaps from others like message persistence at the destination) to write a message down in some medium and LITERALLY toss it to the recipient than it is to radiate the message...

Finding evidence of large-scale 'macro-engineering' projects around other stars may be our best chance of detecting other civilizations. So says Milan ?irkovi? (Astronomical Observatory of Belgrade) in a paper discussed here yesterday. But what would make us think such structures exist? Recent microlensing projects have found evidence of objects around distant stars -- we can detect their lensing effect and separate it from that of the parent star. We naturally assume these are planets, but could they be artificial habitats or other system-wide engineering projects? In the absence of direct evidence, we can only speculate, but it seems a not unreasonable assumption that a fraction of advanced technological cultures evolve to the Kardashev Type II stage, capable of controlling the entire energy output of their stars. ?irkovi? relies on recent work by Charles Lineweaver, whose studies of the 'galactic habitable zone' show that Earth-like planets within it would be on average 1.8...

If advanced technological civilizations are out there, how do we go about detecting them? Conventional SETI, beginning in 1960 with Frank Drake's investigations of Tau Ceti and Epsilon Eridani, has focused largely on the reception of targeted information via radio. More recent optical SETI likewise hunts for beacons from a civilization attempting some form of contact. But it was Freeman Dyson who suggested that if advanced civilizations exist, their very presence should make them detectable. The Dyson shell is what a civilization running out of living space and energy on planetary surfaces may build. Conceivable in numerous variants (and apparently inspired by Olaf Stapledon's 1937 novel Star Maker), it is essentially a technology surrounding a star to exploit all its energy output. As summarized in a new paper by Milan ?irkovi? (Astronomical Observatory of Belgrade), Dyson's solution serves not only as a way of capturing all energy from the home star, but also as a potential marker...

The red rain that fell in the Indian state of Kerala continues to create interest. Are the particles found suspended within it extraterrestrial in nature? The rain first fell on the 25th of July, 2001, but red rain phenomena continued to occur for two months thereafter, although in some cases other colors appeared, and there are reports of colored hailstones. This was no one-shot event. I've held off on this story hoping to get further information, but enough readers have asked for details that I'll go with what we now have. We know this much: The red color is caused by the mixing of microscopic red particles with the water, the characteristics of which are unusual. As noted by Godfrey Louis and Santhosh Kumar (Mahatma Gandhi University) in their paper on the subject, the particles vary from 4 to 10 microns in size and appear under magnification as red-colored glass beads. Electron microscope work shows them to have "...a fine structure similar to biological cells." And although they...

Optical SETI has generally adopted the conventions of conventional SETI by targeting nearby, Sun-like stars. It's a strategy that makes sense, but given the number of potential transmitting stars and the need for broader surveys, what we'd ultimately like to find is a strategy for optimizing our chances, a way of looking for optical signals from other civilizations that both we and the transmitting civilization could deduce. That's the challenge Seth Shostak (SETI Institute) and Ray Villard (Space Telescope Science Institute) take on in a paper called "A Scheme for Targeting SETI Observations." So what makes immediate sense as a method of star targeting? Something that is sufficiently repeititive to be used as a kind of pointer. Shostak and Villard argue for planetary transits as a way of providing temporal synchronization between distant civilizations. A transmitting society could time its signal to be sent during the transit as observed from the transmitter, or timed to arrive when...

I see that SETI@home is concerned about being able to continue its matching funds program from the University of California and is actively soliciting donations. It's a terrific project, of course, and the numbers are staggering: with early expectations of raising 100,000 participants, SETI@home wound up with 5.4 million volunteers who donated 2.4 million years of processing time. A new data recorder at Arecibo and juiced up operating software make the program more potent than ever, and certainly worthy of support. Also on the SETI front is the Planetary Society's dedication of the first telescope exclusively devoted to optical SETI (OSETI). The Harvard-based observatory includes a 72-inch primary mirror that is larger than any U.S. optical telescope east of the Mississippi. Performing one trillion measurements per second and expanding existing optical searches by 100,000-fold, the new installation will search for laser signals that can far outshine the light of a nearby star even...

For years now, we've had our eye on Mars rocks that are known to occasionally fall to Earth, blown off their planet of origin in some primeval impact. But recent computer modeling suggests that a reverse process may also occur: rocks from Earth, potentially carrying life, could reach environments as distant as Europa and Titan. The numbers are surprising. As presented by Brett Gladman (University of British Columbia, Vancouver) at the Lunar and Planetary Science Conference, from 30 to 100 objects from Earth would hit Europa after a period of 5 million years. Titan receives 20 hits. The question then becomes, can bacteria survive such a journey, given the violent heat and acceleration that would be involved in blasting them off the Earth? Relevant work at the conference suggests that they can. As summarized by Mark Peplow in a Nature.com article, scientists at the University of Florida (Gainesville) have fired marble-sized pellets into plates containing bacterial spores in water....

Robert Carrigan (Fermi National Accelerator Laboratory) drew quite a bit of attention last summer when he suggested that SETI signals could contain harmful information, perhaps created by a so-called 'SETI hacker.' Carrigan's article has now appeared in Acta Astronautica, and it's stuffed with beguiling ideas even if you find the premise unlikely. "...will a SETI signal be altruistic, benign or malevolent?" Carrigan asks. "It would help to understand the motivations of a message before reading too much of it. Like Odysseus, we may have to stuff wax in the ears of our programmers and strap the chief astronomer to the receiving tower before she is allowed to listen to the song of the siren star." That's fascinating stuff, recalling Fred Hoyle's A for Andromeda and Carrigan's own The Siren Stars, written with Nancy Carrigan and serialized in Analog in 1970. But this new paper is worth reading for reasons other than the hacker hypothesis; its author speculates widely on SETI itself....