Given how much we do not know about everything from abiogenesis to the lifetime of technological civilizations, what can we say about SETI's chances for success? Henry Cordova, a Centauri Dreams regular, is a long-time SETI enthusiast who has nonetheless been revising his thinking on the discipline's prospects. Our one useful sample, Earth, tells us how long it took for life just to become multi-cellular, much less to reach the tiny window opened by our technological society. And need we assume that intelligence will inevitably arise even with complex biology to support it? A retired geographer and mapmaker currently living in southeast Florida, Henry served in the US Navy and was originally trained as an astronomer and mathematician. Amateur astronomy, celestial navigation and collecting star atlases occupy his time when he's not pondering questions like how civilization might arise without technology, or whether Dysonian strategies -- looking not for beacons but evidence in the...

Harmonizing with yesterday's post about a NASA grant to study technosignatures is word from Breakthrough Listen, which has released a catalog of what it calls 'exotica' or, to cite the accompanying paper: "an 865 entry collection of 737 distinct targets intended to include "one of everything" in astronomy." The idea is to produce a general reference work that can guide astronomical surveys and, in the case of Breakthrough, widen the search for technosignatures. Brian Lacki (UC-Berkeley), who is lead author of the new catalog, notes that it's not meant to be restricted to SETI, though its uses there may prove interesting. Here are the four categories of exotica the catalog defines: 'Prototypes.' Here the intent is to list one example, perhaps more, an archetype of every known type of non-transient object in the sky. According to the paper, "We emphasize the inclusion of many types of energetic and extreme objects like neutron stars..., but many quiescent examples are included too."...

What a pleasure to see -- after three decades -- a grant from NASA for a SETI project, and on technosignatures at that. NASA's history with SETI has been a challenging one given the subject's reception in Congress. It was in 1971 that the agency funded Barney Oliver's study on the huge array called Project Cyclops, whose price-tag would have been astronomical, but the report in which it was described provided numerous insights into the SETI effort. NASA's engagement with SETI later came under fire from William Proxmire in the Senate, resulting in the termination of SETI funding in 1982. Proxmire would later change his mind on SETI's value. Even so, the NASA Microwave Observing Program (MOP) planned as a search of 800 nearby stars in the early 1990's was again targeted in Congress and canceled shortly thereafter. The SETI effort developed in the ensuing years without government funding through efforts like Project Phoenix, which picked up the Mobile Observing Program under the...

Yesterday we looked at a new paper from Robert Gray on the possibility -- even likelihood -- that the kind of signal SETI is looking for would be intermittent in nature rather than continuous. The numbers tell the story: In Gray's calculations, an isotropic transmission with a range of 1,000 light years -- i.e., a continuous beacon broadcasting in all directions -- requires on the order of 1015 W to produce the kind of signal-to-noise ratio that would allow us to pick it up with facilities like those used in current SETI searches. 1015 is a big number, going beyond the current terrestrial power consumption of 1013 W by orders of magnitude and reaching 1 percent of the total power received by Earth from the Sun. Reduce the desired range of the signal to 100 light years and the requirement for isotropic broadcasts is still daunting, demanding something like 1013 W, or 10,000 1,000 MW power plants. As Gray puts it: The large power required for continuous isotropic broadcasts could...

My guess is that most people think of SETI as doing a 'long stare' at a given star, on the theory that it may take time to acquire a possible signal from an extraterrestrial civilization. But in reality observations take place over short time periods. The Mega-channel ExtraTerrestrial Assay, known by its acronym as META, led by Harvard's Paul Horowitz and aided by The Planetary Society, could only devote a few minutes to any particular star. The same was true of the follow-on BETA (Billion-channel Extraterrestrial Assay), while targeted searches like Phoenix, led by Jill Tarter and using facilities at Green Bank (West Virginia), the Parkes 64-meter dish in Australia and the 300 meter radio telescope at Arecibo, still observed targets for less than an hour. The problem with this is that there are numerous reasons why an extraterrestrial signal might be intermittent. We've looked at this issue before, particularly in terms of 'Benford beacons,' as discussed by Greg and Jim Benford in...

When Ken Wisian and John Traphagan (University of Texas at Austin) published "The Search for Extraterrestrial Intelligence: A Realpolitik Consideration" (Space Policy, May 2020), they tackled a problem I hadn't considered. We've often discussed Messaging to Extraterrestrial Intelligence (METI) in these pages, pondering the pros and cons of broadcasting to the stars, but does SETI itself pose issues we are not considering? Moreover, could addressing these issues possibly point the way toward international protocols to address METI concerns? Ken was kind enough to write a post summarizing the paper's content, which appears below. A Major General in the USAF (now retired), Dr. Wisian is currently Associate Director of the Bureau of Economic Geology, Jackson School of Geosciences at UT. He is also affiliated with the Center for Space Research and the Center for Planetary Systems Habitability at the university. A geophysicist whose main research is in geothermal energy systems, modeling,...

If we could somehow rewind time to the earliest days of the Solar System and start over again, would life -- and intelligence -- reappear? It's an experiment science fiction authors are able to try, but it defies real world science. Nonetheless, we can make approaches to the problem through the analysis of probabilities. In particular, we can use statistics, and the technique known as Bayesian inference, which weighs probabilities updated by new evidence. This is a helpful exercise given that so often I hear people referring to the idea that intelligent life must be everywhere because the universe is so vast and there are so many opportunities for it to arise. But does life inevitably emerge on what we might consider habitable worlds? What if this process of abiogenesis is rare? The question points to the fact that we have absolutely no idea what the likelihood is, and therefore assumptions about intelligent life based solely on numerical opportunity are nothing but speculations....

In our continuing look at biosignatures that could flag the presence of life on other worlds, we've sometimes considered the so-called 'red edge,' the sharp change in reflectance of vegetation that shows up in the near-infrared. It's worth remembering that vegetation is the largest reflecting surface on Earth (about 60 percent of the land surface), with an increase in reflectance that shows up around 700 nm. As Alex Tolley explains below, the red edge may shift depending on the evolution of plant life and the variables, including light intensity but comprising many other factors, that would affect life on M-dwarf planets. These are the first whose atmospheres we'll be seriously examining for biosignatures, and the question of how to extrapolate from Earth life to environments as exotic as these is complex. A Centauri Dreams regular, Alex reminds us that vegetative life may prove adaptable in ways that will surprise us. by Alex Tolley Artist’s conception of Proxima Centauri b. Credit:...

Is seeding life into the universe to be a part of the human future? Space probes conceivably could be doing this inadvertently, and the processes of panspermia also may be moving biological possibilities between planets and even stars. Robert Buckalew has his own take on what humans might do in this regard, as discussed below. Robert has written fiction and non-fiction since 2013 under the pen name Ry Yelcho for the blog Yelcho's Muses. In 2015 he received the Canopus Award for Excellence in Interstellar Fiction from 100 Year Starship for the story "Everett's Awakening." His short story "The Interlopers" appears on Literally Stories. What follows draws on his speculative science article "Microbots—The Seeds of Interstellar Civilization," which was awarded the Canopus Award for Original Non-Fiction. The essay that follows is based on his presentation at the Icarus Interstellar Starship Congress 2019. by Robert Buckalew The series of pivotal events that led to the development of...

Reykjavik is an old haunt of mine, a favorite place to which I have not returned in all too long. I was delighted, then, to hear from Angelle Tanner, who in August attended the Extreme Solar Systems IV conference there. I had the pleasure of getting to know Dr. Tanner in Knoxville when we both spoke at a biosignatures session at the 2017 symposium of the Tennessee Valley Interstellar Workshop. Dr. Tanner received her PhD at UCLA, did postdoc work at both Caltech and Georgia State, and is now an associate professor at Mississippi State University. Her work specializes in exoplanet detection and programs devoted to understanding the properties of stars that host planets, as well as the architecture of the systems that evolve around them. It's a pleasure to turn today's essay over to Dr. Tanner for a look at exoplanetary events in Iceland's capital. by Angelle Tanner Mid-August marked the fourth meeting of the Extreme Solar Systems conference -- this one in Reykjavik, Iceland - touted...

SETI, the Search for Extraterrestrial Intelligence, has kept its focus on the stars, through examination of electromagnetic wavelengths from optical to radio signals. But Jim Benford has been advocating that we consider near-Earth objects as potential SETI targets, prompted by Ronald Bracewell's thoughts in a 1960 paper advancing the 'sentinel hypothesis.' A Bracewell probe could linger in a target system for millions of years, monitoring developments on worlds with the potential for life. Couple that thought with the rarely studied co-orbital' objects that approach the Earth both frequently and closely and you have a map for a realm of SETI that is only now coming into investigation. What follows is a news release from The Astrophysical Journal covering Benford's new paper, one we discussed on Centauri Dreams back in March [see A SETI Search of Earth's Co-Orbitals]. I want to get this out now because Benford will be delivering the 2019 Eugene Shoemaker Memorial Lecture tomorrow,...

Centauri Dreams regular Alex Tolley here examines a new paper with a novel take on Saturn’s moon Enceladus. Tempting us with its geysers and the organic compounds Cassini detected in their spray, Enceladus offers the prospect of life within its internal ocean. But are there other explanations for what we see, pointing to what may be a prebiotic environment? For that matter, what features of life’s chemistry could emerge on such a world without yet maturing into what we would recognize as living organisms? The paper Alex examines offers us quite an interesting take on a possible origin for life not just on Enceladus but elsewhere in the universe. by Alex Tolley Image: "Snow on Enceladus.” Credit: David Hardy. The discovery of subsurface oceans in the icy moons of Europa and Enceladus has increased interest in the exploration of these moons. The logic of the mantra “Follow the water” implies that there may be extant life in these oceans, most excitingly from a unique genesis at...

Breakthrough Listen has just announced a new optical SETI effort in partnership with the VERITAS Collaboration. The news took me by surprise, for VERITAS (Very Energetic Radiation Imaging Telescope Array System) generally deals in high-energy astrophysics, with a focus on gamma rays, which signal their presence through flashes of Cherenkov radiation when they strike the Earth's atmosphere. Here, the array is being used to look for technosignatures, as Andrew Siemion (UC- Berkeley SETI Research Center) explains: "Breakthrough Listen is already the most powerful, comprehensive, and intensive search yet undertaken for signs of intelligent life beyond Earth. Now, with the addition of VERITAS, we're sensitive to an important new class of signals: fast optical pulses. Optical communication has already been used by NASA to transmit high definition images to Earth from the Moon, so there's reason to believe that an advanced civilization might use a scaled-up version of this technology for...

A useful exercise for learning how to look for life elsewhere is to try to find it right here on Earth. Thus Carl Sagan’s observations of our planet via data taken during the 1993 flyby of the Galileo spacecraft, which was doing a gravity assist maneuver enroute to Jupiter. Sagan and team found pigments on the Earth’s surface with a sharply defined edge in the red part of the spectrum. What he was looking at was the reflection of light off vegetation. The ‘red edge’ has become well known in astrobiology circles and is considered a potential biosignature. On Earth, vegetation is the most abundant reflecting surface indicating life (vegetation covers about 60% of present-day Earth’s land surface). The increase in reflectance shows up at about 700 nm, varying in strength depending upon the species of plant. But as Jack O’Malley-James and Lisa Kaltenegger (Cornell University/Carl Sagan Institute) point out, photosynthetic structures containing chlorophyll are found not just in vegetation...

Remember 'Nemesis'? The idea was that mass extinctions on Earth recur on a timescale of between 20 and 40 million years, and that this recurrence could be accounted for by the existence of a faint star in a highly elliptical orbit of the Sun. Put this object on a 26 million year orbit and it would, so the theory ran, destabilize Oort cloud comets, causing some to fall into the inner system at a rate matching the record of extinctions. Thus a cometary bombardment was to be expected on a regular basis, as were the mass extinctions that were its consequence. No one has found Nemesis, though other theories about recurring mass extinctions are in play, including recent work from Lisa Randall and Matthew Reece that explores dark matter as the trigger, with the Sun periodically passing through a disk of the stuff. Of course, finding dark matter itself continues to be a problem. Moreover, the wide range in the proposed recurrences gives rise to the possibility that these events are not...

A paper called “The Natural History of ‘Oumuamua,” just out in Nature Astronomy, puts the emphasis on the word ‘natural.’ We know how much of a stir in the media the interstellar visitor has made given its peculiarities, and the hypothesis put forward by Harvard’s Avi Loeb that it could be a technological object. Now we have a group of 14 astronomers, European as well as American, who have assessed the available data from all angles. This is a worthwhile effort, assembling a team at the International Space Science Institute (ISSI) in Bern, Switzerland that intends to meet once again later in the year. It considers the question of whether the extraterrestrial spacecraft hypothesis is supported by examination of all the peer-reviewed work that has thus far appeared. Matthew Knight (University of Maryland), working with Alan Fitzsimmons (Queen’s University Belfast) assembled the team. Knight believes that natural phenomena can explain ‘Oumuamua: "We put together a strong team of experts...

On Monday I was talking about the rise of open access scientific journals, using the European Space Agency's Acta Futura as just one example. The phenomenal arXiv service, not itself a journal but a repository for preprints of upcoming papers, is already well known in these pages. Now we have the largest public release of SETI data in the history of the field, a heartening follow-through on a trend that broadens the audience for scientific research. Breakthrough Listen is presenting two publications in the scientific literature (available as full text, citation below) describing the results of three years of radio and optical observations, along with the availability of a petabyte of data from its work at the Green Bank instrument in West Virginia and the Parkes Radio Telescope in Australia. This covers a sample of 1327 nearby stars (within 160 light years from Earth) and builds on the team's results on 692 stars as presented in 2017. No signs of extraterrestrial civilizations turn...

If you want to look for possible artifacts of advanced civilizations, as do those practicing what is now being called Dysonian SETI, then it pays to listen to the father of the field. My friend Al Jackson has done so and offers a Dyson quote to lead off his new paper: "So the first rule of my game is: think of the biggest possible artificial activities with limits set only by the laws of physics and look for those." Dyson wrote that in a 1966 paper that repays study today (citation below). Its title: The Search for Extraterrestrial Technology." Dysonian SETI is a big, brawny zone where speculation is coin of the realm and the imagination is encouraged to be pushed to the limit. Jackson is intrigued, as are so many of us, with the idea of using the Sun's gravitational lens to make observations of other stars and their planets. Our recent email conversation brought up the name of Von Eshleman, the Stanford electrical engineer and pioneer in planetary and radio sciences who died two...

I'll wrap up this three-part series on 'lurker' probes and ways of finding them with Keith Cooper's provocative take on the matter. A contributor to Centauri Dreams whose far-ranging ideas have fueled a number of dialogues here (see the archives), Keith is editor of Astronomy Now and the author of the upcoming book The Contact Paradox: Challenging Assumptions in the Search for Extraterrestrial Intelligence. I've read the manuscript and can tell you that you're going to want this one on your shelves. Today, Keith takes us into the practical realm. If we were to find a Bracewell probe in our Solar System, what would we do with it? Who might discover it, who would claim its technologies, and what, under international law, would be its legal status? Plenty of material for science fiction plots here as we embark on the search to see what's out there among Earth's co-orbitals. by Keith Cooper It's enough to keep me awake at night. Suppose that an extraterrestrial probe is discovered in our...

Because I've been re-reading Gregory Benford's Galactic Center sequence (now into Furious Gulf), I want to quickly mention the galactic center simulation available here, which offers a 360-degree, ultra-high-definition view based on Chandra X-ray observations as massaged by NASA supercomputers. It's lively stuff, showing "the effects of dozens of massive stellar giants with fierce winds blowing off their surfaces in the region a few light years away from the supermassive black hole known as Sagittarius A* (Sgr A* for short)." Just remember Greg got there first. But back to the probe question we've been examining. Jim Benford's take on a SETI search for 'lurkers,' probes that fit into the Bracewell category, examines targets known as Earth co-orbitals, as we saw on Friday. UCI physicist Greg Benford's comments about his brother's article examine the question of what the presence of such a probe in our system might imply. The possible scenarios take us into the realm of what Greg has...