by James and Gregory Benford Interstellar beacons continue to draw discussion, and the Benford brothers now return with further thoughts on the matter in response to reader comments here. How to distinguish a beacon from a natural source, and why consider it in terms of cost? The answer is below, as is an interesting twist on the Fermi paradox. We proposed making cost a useful, perhaps universal, standard because it is a quantitative constraint. Our aim is to help observers look for plausible beacons that may exist. Using transient events seen by observers is an economic way to ask these next, exploratory questions. Speculations always yield to data, and at its 50th anniversary SETI needs a vital data point: first detection. In our latest work, we point out that researchers should be aware of the likely properties of beacons. In particular, beacons may mimic pulsars in repetition rate. But they would distinguish themselves in some way, such as amplitude modulation, varying pulse...

Recently we looked at James and Gregory Benford's thoughts on interstellar beacons, noting that using cost as a likely constraint allowed the authors to discuss how cost would affect design, and therefore the parameters of any beacon we would be likely to observe. But what is it about interstellar beacons that sets them apart from transient phenomena? After all, it was no longer ago than 1963 that Nikolai Kardashev proposed that the radio source CTA 102 could be evidence of a Type II or III extraterrestrial civilization (i.e., one that is able to use the entire energy output of its star, or in the most extreme case, of its entire galaxy). When Gennady Sholomitskii announced his observation that CTA 102's radio emission was varying, something of a sensation ensued. Those of us of a certain age can recall Roger McGuinn's song 'CTA 102,' written and performed by McGuinn's group The Byrds. It was on their Younger Than Yesterday LP, released in 1967. A sample: CTA 102 Year over year...

by James & Gregory Benford Talk of interstellar beacons invariably heats up the discussion, and I was fascinated to read not only Bob Krekorian's take on the concept, but the follow-up comments of James and Gregory Benford, whose work on beacons has been examined previously in these pages. See A Beacon-Oriented Strategy for SETI, as well as Jim Benford's Regarding METI and SETI Motives and Jon Lomberg's Interstellar Beacons: A Silence in Heaven? for our treatment of this topic. Meanwhile, what about putting some constraints on how an interstellar beacon would operate? Here are the Benford brothers with a look at one way to proceed. Bob Krekorian's ideas invite comments. He takes a simple model which has the virtues of minimizing Doppler shifts in SETI beacons: an outward-facing array in an AU scale orbit around a star, fed by solar panels and radiating outward. The concept isn't fleshed out quantatively, so can't be compared to approaches such as ours. And of course he couldn't say...

If we're going to get lucky with SETI, it's probably going to be through the reception of an interstellar beacon rather than the chance detection of an electronic emission from space. Sure, chance catches are possible, and for all we know odd receptions like the WOW! signal of 1977 might be cases in point. But we can't confirm such signals because they're one-shot affairs, whereas a beacon, designed to be received over interstellar distances, just might give us other options. Understanding the Interstellar Beacon So what can we say about beacons? In a guest editorial for the SETI League, former NASA SETI signal detection analyst Bob Krekorian takes a shot at the problem. Krekorian assumes a space-faring species will put its transmitter inside the habitable zone, designed to exist as close to the parent star as feasible to take advantage of the huge amounts of energy available there. If we were building such a beacon, we might decide to place it between the orbits of Earth and Venus,...

What are the odds for survival of a technological society? We don't know yet, having but one example to work with, but it's interesting to speculate, as Ray Villard does in a recent online post, about the kinds of intelligence that may evolve in the universe. All too often we equate technology with intelligence, which may skew our view of projects like SETI. Energized by the American Association for the Advancement of Science meeting in San Diego last week, Villard is thinking that intelligent life may have appeared on our planet not once but twice, and one of those life-forms is never going to be found by listening to radio wavelengths. The case for cetaceans seems strong. Here's Villard on the matter: Physiologically, dolphins have a brain architecture and brain mass-to-body mass ratio that is closer to that of humans than for any other species on Earth. Many years of experiments on captive dolphins show that they are self-aware, have a sense of self-identity, do detailed problem...

Panspermia, the idea that life might travel through space to seed other planets and even other star systems, is a fascinating topic for conjecture, and our understanding of the survival of various forms of life in extreme environments only adds to its appeal. But just as SETI has an active counterpart that seeks to send rather than simply receive interstellar messages, so panspermia has its own advocates for a new kind of mission: To seed the stars from Earth. A group called SOLIS (Society for Life in Space) has sprung up around the notion. Its goal: To propagate our family of organic Life throughout the Milky Way Galaxy and beyond. We propose to seed young planetary systems in star-forming interstellar clouds. We shall design and launch directed panspermia missions carrying the microbial representatives of Life by the year 2050. So says the SOLIS Web site and so says society coordinator Michael Mautner, who is a research professor in chemistry at Virginia Commonwealth University....

Suppose a civilization somewhere in the cosmos is approaching Kardashev type III status. In other words, it is already capable of using all the power resources of its star (4*1026 W for a star like the Sun) and is on the way to exploiting the power of its galaxy (4*1037 W). Imagine it expanding out of its galactic niche, turning stars in its stellar neighborhood into a series of Dyson spheres. If we were to observe such activity in a distant galaxy, we would presumably detect a growing void in visible light from the area of the galaxy where this activity was happening, and an upturn in the infrared. Call it a 'Fermi bubble.' That's the term used by Richard Carrigan (Fermi National Accelerator Laboratory) in his latest work on what he calls 'interstellar archaeology,' the search for cosmic-scale artifacts like Dyson spheres or Kardashev civilizations. A Fermi bubble would grow as the civilization creating it diffused through space. Carrigan notes that, as Carl Sagan and others...

As I'm just finishing up Richard Holmes' The Age of Wonder (Pantheon, 2009), the Royal Society had been on my mind even before the two-day conference on SETI that concluded yesterday made the news. If you haven't read the Holmes book, by all means do so. It's a fascinating study of the development of science and the imagination in the late 18th Century and into the Romantic era, with cameos by the likes of Shelley and Keats and in-depth discussions of everyone from Pacific voyager Joseph Banks to the chemist Humphry Davy. It's a cliché to say I couldn't put the book down, but this one fully deserves the compliment. With the Royal Society now in its 350th year, a conference steeped in SETI and questions of astrobiology seems made to order as we track the data from our far-flung space observatories. I wanted to mention that Paul Davies' public lecture at the conference, called "The Eerie Silence: Are We Alone in the Universe," will be made available at the Royal Society video...

We've long speculated about astrobiology on planets around stars like the Sun, and lately the thinking has moved to M-class dwarfs and whether or not they could be circled by habitable planets. But what about massive stars, classes A and B, where we're looking at two to fifteen times the mass of the Sun? New work from the Harvard-Smithsonian Center for Astrophysics (CfA) and the National Optical Astronomy Observatory (NOAO) tells us that planets form readily around such stars, leading Xavier Koenig (CfA) to tell a press conference at the AAS meeting this week in Washington, "We see evidence of planet formation on fast forward." Make no mistake, massive stars present a challenging environment for planet formation. Their disks may be packed with useful material for building worlds, but the intense stellar radiation and winds from these stars work to destroy the disks in relatively short order. Koenig and colleagues looked at the star-forming region W5, some 6500 light years away in the...

by Joe Davis Yesterday we followed Joe Davis' adventures in Puerto Rico as he arranged for the transmission of a message to the stars near the 35th anniversary of the famous message to M13, sent from the same site in 1974. Today Davis concludes the story, with a look at how the 'RuBisCo' message was put together, and thoughts on the ins and outs of getting unusual projects approved in today's scientific climate. I had a sort of showdown with Arecibo's interim Director, Dr. Michael C. Nolan at the last minute and Danielle Hofmans' detailed notes have made it possible for me to recount that conversation here. Nolan's main problem was about politics. Arecibo once received a "Golden Fleece" award from Senator Proxmire for its involvement with the search for extraterrestrial intelligence, including its role in the Sagan-Drake transmission of 1974. That recollection has special resonance now since there are very serious ongoing concerns about future funding for the observatory. Nolan...

by Joe Davis We've looked before at the work of MIT biology research affiliate Joe Davis, whose passion is the melding of science and art. Among his many ideas are the creation of an 'infogene,' engineering a sign of human intelligence into the genome of bacteria that could be flung into the heavens by the trillion, and a three-masted Gulf Coast tower that would discharge laser beams into the sky. In 1986, Davis used MIT's Millstone radar to beam a signal to Epsilon Eridani, Tau Ceti and two other stars. His most recent adventure takes him to the great telescope at Arecibo. It involves the 35th anniversary of the Drake/Sagan transmission to M13, a messaging strategy based on molecular biology, and the emergence of the coolest iPhone in the world. What follows is a narrative describing events that took place just over one week ago: I traveled from Boston to Puerto Rico on 03 November to deliver a lecture for the University of Puerto Rico's Biology Colloquium (Rio Piedras campus) in...

Habitability is always a matter of definition. Is it a measure of suitability for human life? Or do we take the larger astrobiological view that it's based on suitability for microbial life, in which case we go from a narrowly defined habitable zone here in our Solar System to one that could potentially stretch from the upper atmosphere of Venus to the suspected subsurface aquifers on some Kuiper Belt objects. But these qualitative definitions have thus far lacked a quantitative counterpart, a method to quantify and compare potentially living worlds. The matter has drawn the attention of Abel Mendez (University of Puerto Rico, Arecibo), who discussed his quantitative evaluation of planetary habitability at the Division for Planetary Sciences meeting this week in Fajardo, Puerto Rico. One of his results stands out immediately. Using finely tuned planetary models, Mendez found that among Mars, Venus, Europa, Titan and Enceladus, the latter has the highest subsurface habitability. That...

by James Benford I first talked to Jim Benford back in 2003, discussing his work (wih brother Gregory) on microwave beam propulsion. He had already run experiments at the Jet Propulsion Laboratory demonstrating acceleration on a lightsail using these techniques, and was then hoping to run an experiment on The Planetary Society's ill-fated Cosmos 1. The founder of Microwave Sciences, Benford's earlier work at Physics International led to the development of the largest high power microwave experimental facility in the country. Along with continuing work on sail beamed propulsion concepts, the physicist has been actively studying questions of SETI and METI, musing on the kind of beacons we might find and the motivations for building them. Herewith some thoughts inspired by recent discussions in these pages. We explored the motives for a civilization broadcasting to the galaxy at large (which I call Beacons, as they're not targeted at specific stars) in one of the two papers we did last...

by Jon Lomberg It seems fitting that we should be in the midst of a three-part series on SETI and METI issues. As Larry Klaes reminded me in a recent comment, September 19th was the fiftieth anniversary of the paper that began the modern SETI era, Morrison and Cocconi's "Searching for Interstellar Communications" (available here). Artist, lecturer and polymath Jon Lomberg now adds his own take on the discussion. Pay particular attention to the question of signal duration -- would a METI signal be continuous or intermittent? Much rides on the answer. Lomberg is a familiar figure to Centauri Dreams readers. Creator of the Galaxy Garden (Kona, Hawaii), Jon is an astronomical artist working in many media whose work is known throughout the space community and beyond. Viewers of COSMOS will know that he was chief artist on that project, serving as Carl Sagan's principal artistic collaborator for many years. His splendid work on CONTACT, where he storyboarded many of the film's astronomical...

?by Larry Klaes About a decade ago while attending a SETI conference, I was listening to a researcher give a talk about detecting messages from other galaxies such as the giant elliptical galaxy Messier 87 and the immense Virgo galactic cluster it resides in. Since M87 is about 60 million light years from the Milky Way, I later asked him why would someone send a message that they could not hope to get a reply to for 120 million years at the least. His reply was rather vague and dissatisfying to me. It was along the lines of they would do it for the sake of being able to sending such a message across such a vast distance and time. I was left with the impression he did not fully think out why any intelligence would send messages across millions of light years of intergalactic space with even less hope of a reply than our token METI (Messaging ExtraTerrestrial Intelligence) effort with Messier 13 in 1974 via Arecibo, for which we will need to wait 50,000 years for the quickest reply...

Chalk up another win for the 'life is ubiquitous' school of thought. We now know that when the Stardust spacecraft passed through the gas and dust surrounding comet Wild 2 back in 2004, it captured samples that include glycine. Living things use glycine to make proteins, which made the preliminary detection of this amino acid a significant event, though one that had to be carefully analyzed. After all, terrestrial contamination could have accounted for the glycine gathered up by Stardust. Image: The comet Wild 2 as imaged by the Stardust spacecraft. Credit: NASA/JPL. Ensuing work, however, has ruled out the contamination scenario. The space-gathered samples show significantly more Carbon 13 than glycine from Earth, an isotopic marker that identifies the material as originating in the comet. That gets us back to a welcome thought, that life is common in the universe. Carl Pilcher (NASA Astrobiology Institute) has this to say: "The discovery of glycine in a comet supports the idea that...

When it comes to exoplanet speculations, we're still in the era when data are few and dominated by selection effect, which is why we began by finding so many 'hot Jupiters' -- such planets seem made to order for relatively short-term radial velocity detections. It's a golden age for speculation, with the promise of new instrumentation and a boatload of information from missions like Kepler and CoRoT to be delivered within a few years. What an extraordinary time to be doing exoplanetary science. The big questions can't be answered yet, but it shouldn't be long before we have an inkling about what kind of stars are most likely to produce terrestrial planets. And maybe a qualification is in order. M-dwarfs are so common in our galaxy -- some estimates run to seventy percent of all stars and up -- that finding habitable worlds around them would hugely increase the possible venues for life. But is there any way we could call planets around M-dwarfs 'Earth-like?' Maybe in terms of...

An exotic planetary environment right here in the Solar System may be a useful test for answering the key question of how common life is in the universe. So argues Jonathan Lunine (University of Arizona) in an upcoming paper. Lunine believes there is a plausible case for life to form on Titan, and that if we were to find it there, its very dissimilarity from Earth would make it a test-case for life in other extreme environments of the sort that may be common in the cosmos. We'd like to answer this question locally because it may be some time before we can answer it around other stars. After all, the best spectral signatures we can hope to get from the atmospheres of Earth-analogues elsewhere are quite possibly going to be ambiguous. Molecular oxygen can be a sign of photosynthesis but also of the abiotic escape of water from the upper atmosphere. Methane in the same atmosphere makes biology more likely but may be, Lunine thinks, difficult to detect from Earth. Image: One way to...

Does complex life emerge at a gradual, uniform rate? If so, we can come up with one answer to the Fermi paradox: We have not detected signs of extraterrestrial life because the time needed for complex life to appear generally exceeds the life of a star on the main sequence. But the assumption that intelligence appears over time with a gradual inevitability -- a key tenet of work by Brandon Carter, Frank Tipler and others in the 1980s, may not in fact be true. Solar system-wide events connect life with its stellar environment, while galaxy-wide events provide yet another context. Punctuated Evolution Among the Stars Milan ?irkovi? (Astronomical Observatory, Belgrade) and colleagues have much to say about this in a new paper in Astrobiology. It's a rich treatment of our older assumptions and newer thinking about punctuated evolution, the idea that life actually evolves in spasms rather than smooth ascents. Species remain relatively stable for long periods but endure sudden changes that...

As we contemplate using long-range tools like spectroscopy to examine distant exoplanets for life, we're also developing the hands-on equipment we'll need for seeking it out in our own Solar System. Project SLIce (Signatures of Life in Ice) is a case in point, an attempt to study how organic material behaves in ice on other worlds by using Earth settings as an analogy. On that score, the archipelago of Svalbard has proven to be a helpful testbed. Located in the Arctic Ocean between Norway and the North Pole, Svalbard is icy and spectacular. The image below conjures up memories of a nautical journey I took around Iceland in the 1970s, with white-capped seas pushing up against snow-clad peaks. The SLIce team sees Svalbard as a laboratory for looking for extant or extinct life, and a place to develop the protocols for working with rovers in operating environments like Mars. Image: I love Iceland, but pushing as far north as Svalbard would really bring out the adventurer in me. Here we...