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....

Readers who know of Centauri Dreams' fascination with 'deep time' will not be surprised that I am working on a side project involving past, not future time. Specifically, a study of the Eocene, that remarkable period beginning some 55 million years ago during which the ancestors of most modern mammals -- including the higher primates, such as apes, monkeys and man - appeared. And if the Eocene, 2/3 of the way back to the age of the dinosaurs, seems like a long reach from interstellar travel, ponder this: the more we learn about how life adapts to changing planetary environments, the better we'll be able to carry out the hunt for life around other stars. On that score, it's interesting to see that a team supported in part by NASA's Exobiology program has determined that Earth's continents were in place soon after the planet formed. The Earth was not, in other words, a purely ocean world in that era, or a barren, inhospitable place like the Moon. Analyzing the occurrence of a rare...

"We may never find other life away from Earth, but we have already made aliens on this planet and we will continue to do so at an increasing pace," says Peter Ward, author of Life As We Do Not Know It: The NASA Search for (and Synthesis of) Alien Life (Viking, 2005). "In the last five years we've come to realize that we can make microbial life in a lot more ways than Mother Earth did." Aliens on this planet? Ward is talking about laboratory work here on Earth that has modified life as we commonly understand it. That includes creating microbes with at least one amino acid beyond the 20 found in the DNA of native Earth life. Genetic modification also constitutes, in Ward's view, the creation of an alien lifeform, as does modifying a lifeform to reduce its complexity. Ward, a paleontologist who studies these matters within the University of Washington's astrobiology program, is perhaps best known to Centauri Dreams readers as the co-author (with Donald Brownlee) of Rare Earth: Why...

Yesterday we looked at Milan ?irkovi?'s paper “The Temporal Aspect of the Drake Equation and SETI" (Astrobiology Vol. 4 No. 2, pp. 225-231), and pondered whether there might not be a 'communications window' -- an interval for any society between when it reaches the technological capacity for interstellar communication and the point when it becomes a 'supercivilization' unlikely to use conventional SETI methods to contact us or anyone else. If so, that 'window' would have a profound effect on how many civilizations we might be able to contact via SETI, and would thus change our answers to the Drake Equation. But there are other kinds of assumptions built into the equation that may be problematic. ?irkovi? notes that the equation assumes a more or less uniform physical and chemical history of our galaxy, but uniformitarianism doesn't work well in astrophysics or cosmology (think of the Steady State theory -- uniformitarian -- vs. the Big Bang, which introduced the concept of epochs...

The famous Drake Equation was developed as a way to estimate how many technological civilizations might exist and thereby be targets for SETI research. Conceived in 1961 as astronomer Frank Drake worked at the National Radio Astronomy Observatory (Green Bank, WV), the equation exists in a variety of forms depending on which authors you consult (see, for example, this SETI Institute discussion of the equation). But all variants draw on the same idea: to study extraterrestrial civilizations, you must consider such factors as: the mean rate of star formation in the Galaxy; the fraction of stars that can support life; the fraction of stars that have planetary systems; the number of planets per system with conditions suitable for life; the number of planets where life does originate and evolve; the fraction of planets where intelligent life forms develop; the fraction of planets where intelligent life develops technology; and a final, crucial measure: the mean lifetime of a technological...

To make life happen you need organic molecules that contain nitrogen. Now new work at NASA's Ames Research Center, to be reported in the October 10 issue of the Astrophysical Journal, reveals that organic molecules found throughout the galaxy do, in fact, contain nitrogen. "Our work shows a class of compounds that is critical to biochemistry is prevalent throughout the universe," said Douglas Hudgins, an astronomer at NASA Ames and principal author of the study. The studies combined laboratory experiments and computer simulations. We already knew, thanks to the Spitzer Space Telescope, that complex organic molecules called polycyclic aromatic hydrocarbons (PAHs) are all but ubiquitous. Learning that PAHs contain nitrogen implies that the building blocks of life are seeded everywhere in the universe. From a NASA Ames news release, quoting astrochemist and team member Louis Allamandola: "Chlorophyll, the substance that enables photosynthesis in plants, is a good example of this class...

If you're looking for a terrestrial analogue to one part of the Martian environment, you could do worse than the ice vents inside a frozen volcano on the Norwegian island of Svalbard. There, in a one million year old volcano called Sverrefjell, a team of researchers has found a community of microbes both living and fossilized. Ice-filled volcanic vents are believed to occur on Mars and may well be a potential habitat for life on the planet. Behind the Svalbard investigations is AMASE, the Arctic Mars Analog Svalbard Expedition, which is designing devices and techniques that may one day be used by automated landers to search for life on Mars. And thus far the findings are promising. The team has been able to perform its tests while maintaining scrupulous sterility, a key factor in ensuring that 'life' detections on another planet aren't simply the result of Earthly microorganisms being introduced into the local ecology. Examining 780-million year old sedinmentary rocks, the team also...

The search for extraterrestrial intelligence (SETI) has seen a great deal of publicity, from television programs interviewing involved scientists to blockbuster movies like Contact. But the idea that there might be signs of extraterrestrial life closer to home has received relatively short shrift. Nonetheless, SETA (the search for extraterrestrial artifacts) has spawned interesting work, from Gregory Matloff's examinations of anomalous Kuiper Belt objects to Robert Freitas' surveys of 'halo orbits' around the Lagrangian points. So far both kinds of search -- SETI and SETA -- have come up short, but a few curious things have been observed on each side. One interesting SETA investigation involved an object called 1991 VG, which made a close approach to Earth in 1991 (thanks to Adam Crowl for bringing this one to my attention). Discovered by Jim Scotti using the University of Arizona's Spacewatch telescope (normally used to detect small asteroids near the Earth), 1991 VG seemed to be...

Space artist Jon Lomberg, whose work illustrated yesterday's entry on the white dwarf star GD 362, wrote recently with a comment on Centauri Dreams' September 8 story on Titan. The story discussed new theories on Titan as an abode for life, citing a presentation at the recent Division of Planetary Sciences meeting in Cambridge and quoting Southwest Research Institute scientist David Grinspoon on the possibilities inherent in Titan's abundant hydrocarbons and acetylene, which might help power a metabolism. Titan, of course, is a very cold place, which would seem to inhibit the needed chemistry. But Lomberg points out a way around the problem: "Consider the organic superconductor dimethyltetra-thiofulvalene tetracyano-quinodimethane. Discovered in the 1970s, this was the first organic superconductor found, and it remains superconductive at [relatively] high temperatures. More have been discovered since. When Carl Sagan and I were working on my Encyclopedia Galactica series of...