Thoughts on Enceladus as a home to life have kept astrobiological debate lively, an unexpected but welcome development from the Cassini mission. The interest is understandable: Cassini has shown us plumes that seem to be the result of some kind of geothermal venting, with liquid water and geothermal energy sources all possible drivers for the formation of life. We don't exactly know what's going on here, but the possibility of a hydrological cycle -- liquid, solid, gas -- has kept theorists active, as witness a research note by Christopher Parkinson (Caltech) and team. The early Earth serves as a possible model for life elsewhere. With photosynthesis not available, life would depend on abiotic sources of chemical energy. It's believed this would have come in the form of oxidation-reduction processes driven by factors like hydrothermal activity, impacts, electrical discharges, or solar ultraviolet radiation. Organics may have been synthesized from inorganic molecules near submarine...

Just off the phone with Seth Shostak, I can report that the KTVU story discussed below about a possible SETI reception is bogus. Apparently the reporter involved misinterpreted the conversation, as we had surmised. We may get a successful reception of an extraterrestrial civilization's signal one of these days, but this wasn't it.

This looks like a case of extremely poor science reporting, but because I've already received e-mail about it, I will point you to a report from KTVU, a San Francisco television station, claiming that a mystery signal has been received at Arecibo, with obvious SETI implications. Cosmic Variance has also picked up on this and seems as skeptical as I am. A quick call to the SETI Institute revealed there is absolutely no buzz about any sort of successful reception making the rounds there. I have a voicemail in to Seth Shostak in hopes of a comment.

Our recent discussions of active SETI, otherwise known as METI (Messaging to Extraterrestrial Intelligence), highlighted many of the key issues involved while demonstrating just how controversial the topic has become. But is there a way to look at METI experiments more objectively? The San Marino Scale has been widely suggested as a method for assessing the risks we incur with deliberate transmissions from the Earth to other stars. Introduced by Iván Almár in 2005, the Scale is a work in progress that draws on the model of the Richter Scale, which quantifies the severity of earthquakes. The IAA SETI Permanent Study Group continues to work on it, hoping to measure "...the potential exposure of employing electromagnetic communications technology to announce Earth's presence to our cosmic companions, or replying to a successful SETI detection." More on the background of the Scale here. Hungarian theorist Tibor Pacher has been calling my attention to the San Marino Scale for some time,...

When it comes to understanding possible extraterrestrial civilizations, I'm with Freeman Dyson, who had this to say: "Our business as scientists is to search the universe and find out what is there. What is there may conform to our moral sense or it may not...It is just as unscientific to impute to remote intelligences wisdom and serenity as it is to impute to them irrational and murderous impulses. We must be prepared for either possibility and conduct our searches accordingly." As quoted in a 2005 essay by Michael Michaud, Dyson saw two alternatives: Intelligent races may rule their domains with benign intelligence, occasionally passing along the knowledge they have accumulated to a universe eager to listen. Or intelligence may be purely exploitative, consuming what it encounters. We don't know which of these alternatives prevails, if either, and that's one reason that Michaud, a former diplomat who became deputy assistant secretary of state for science and technology, resigned...

Lately I've been thinking about cosmic killers, the kind of extinction events that could destroy an entire ecosphere and any civilization living within it. It's a natural enough thought given our speculations about life elsewhere in the universe. Just how hostile a place is the Milky Way? We're beginning to learn that planets are abundant around stars in our region of the disk, with the encouraging expectation that habitats for evolving lifeforms must be widespread. But maybe there are natural caps other than technological suicide that could end a civilization's dreams. You can't help pondering this when you run into the recent news about a long duration gamma-ray burst (GRB) that took astronomers by surprise. GRBs are normally thought to flag the death of a massive star, but in this case the burst seems to come out of nowhere. What caused the event in a region of space where the nearest galaxy is 88,000 light years away? And no question about GRB 070125's credentials. It was...

One thing I'm always asked when I talk about interstellar topics is how long it would take a spacecraft like Voyager to get to the nearest star. After explaining how far away Proxima Centauri and the slightly farther Centauri A and B really are, I tell the audience that Voyager, if headed in that direction, would be facing a travel time of over 70,000 years. That usually shifts the conversation considerably, because many people assume that if we can get to the outer planets, the nearest stars can't be that far behind. If only it were so. The Centauri stars are, of course, only the closest known (and who knows, perhaps there's a brown dwarf a bit closer). Assume a space technology able to travel at close to the speed of light and you're still dealing with travel times that amount to years, although time for the crew would be shorted according to those interesting Einsteinian effects that cause the crew of a vehicle traveling at 86 percent of lightspeed to experience half the elapsed...

By Larry Klaes Larry Klaes' look at the Allen Telescope Array reminds us of the power of philanthropy at getting serious projects funded. It's a topic we'll be re-visiting as the Tau Zero Foundation comes online early in the coming year. I'm reminded also of the One Laptop Per Child project, which is seeing private donations for these educational tools supplanting government shortfalls in some developing countries. Properly targeted, the philanthropic dollar is a powerful thing, and think of the results if the ATA finds a genuine signal! Cornell astronomer and science popularizer Carl Sagan left quite a legacy in a number of science fields, including and especially those which were considered to be somewhat fringe at one time. One prime example of his support of a science field that was not universally accepted in earlier eras was SETI, the Search for Extraterrestrial Intelligence. At a time when many astronomers did not seriously consider the possibility of other beings existing...

As a coda to our recent SETI discussion, two newspaper stories on the subject ran over the weekend. I follow how the media handle this subject because public interest in SETI seems to remain high, and the cultural expectations that show forth in these articles may give us a glimpse of what would happen in the event of an actual detection. Moreover, the Allen Telescope Array has re-focused attention on this quixotic endeavor. Sometimes it seems that we humans give ourselves too much importance in the cosmic scheme of things. After all, what would our little planet have to offer in a galaxy that, as The Age (Melbourne) notes, is made up of 100 billion stars (and there's that number again, 100 billion, which reminds me that estimates of our Galaxy's stellar population range from this low-ball figure all the way up to Timothy Ferris' whopping one trillion). Aren't humans, we ask, just one more backward species trying to evolve? Maybe, but the problem is that we have no way of knowing the...

When Alexander Zaitsev presented his recent paper at the International Astronautical Congress in Hyderabad (India) recently, he spoke from the center of a widening controversy. The question is straightforward: Should we broadcast messages intentionally designed to be received by extraterrestrial civilizations, thereby notifying them of our existence? Zaitzev, chief scientist at the Russian Academy of Science's Institute of Radio Engineering and Electronics, addressed the question by seeing a necessary relationship between SETI (the search for ETI) and METI (messaging to other civilizations). Indeed, the Russian scientist, working at the Evpatoria Deep Space Center in the Ukraine, has the experience to discuss METI from a practical standpoint. Evpatoria has already transmitted a number of messages, the so-called 'Cosmic Call' signal (1999) being made up of various audio, video, image and data files submitted by people around the world. The later 'Teen-Age Message,' aimed at six...

The Allen Telescope Array, devoted both to SETI and astronomical observations, has begun operations. With 42 radio dishes now active, the array ultimately will be used to scan several billion stars in the Milky Way looking for the signals of an extraterrestrial civilization. That's a staggeringly broad survey, and one that will be followed up by detailed examinations of a million star sample. The ATA is known as Paul Allen's project, but he's joined in philanthropy by the SETI Institute and UC Berkeley, among others. Says Seth Shostak (SETI Institute): "For SETI, the ATA's technical capabilities exponentially increase our ability to search for intelligent signals, and may lead to the discovery of thinking beings elsewhere in the universe. It is the first major telescope in the world built specifically for undertaking a search for extraterrestrial intelligence." It's always interesting to track how the press handles such stories, and this Seattle Times' article plays it straight, with...

Tau Ceti has always been an interesting star, one of two (the other being Epsilon Eridani) that Frank Drake chose as targets for his pioneering Project Ozma SETI observations. The astrobiological interest is understandable. We're dealing with a Sun-like star relatively close (11.9 light years) to Earth. But recent thinking downplays Tau Ceti as a potential home for life. Ponder this: The dust disk around the star seems vastly larger than what we find in our own Kuiper Belt, with deadly implications. Or are they? Let's look more closely. A model of Tau Ceti's disk shows that the mass of small objects up to ten kilometers in size may total 1.2 Earth masses. Compared to our Kuiper Belt's 0.1 Earth masses, this is one massive disk, with ten times the amount of cometary and asteroidal material found in our own system. This despite the fact that Tau Ceti seems to be twice the age of Sol. You might reasonably assume that any Earth-like planet in this system has been bombarded far more often...

Does adenine, a key organic molecule, occur in interstellar dust clouds? If so, those clouds could have delivered the molecule to Earth billions of years ago, a possibility interesting not only in terms of life's formation on this planet but, of course, on other worlds as well. And as University of Missouri chemist Rainer Glaser notes, the idea of space-borne adenine is not implausible, for adenine is known to occur in meteorites and was identified in 1986 in the organic mantle surrounding comet Halley's core. Could adenine have been synthesized on the early Earth? Perhaps, but there are reasons for finding an outside delivery mechanism provocative. Note this from the paper on this work, which appeared in the journal Astrobiology (internal references omitted for brevity). HCN refers to hydrogen cyanide, which can flag the presence of adenine: The idea of prebiotic adenine synthesis on Earth remains controversial. The HCN-based syntheses rely on the presence of a reducing atmosphere,...

James Brown continues to run SETI.net, a privately-funded SETI search program using off-the-shelf components and software created by himself. Brown's work may well be unique, for there seems to be no other working station collecting data that is run by amateur radio astronomers, and that poses a problem for observations like the recent series Brown has made at the frequency and coordinates of the so-called 'Wow Signal,' which was received just over thirty years ago on August 15, 1977. The problem, of course, is that when Brown notes something of interest, he needs corroboration. If you are in the ranks of amateur SETI or radio astronomy enthusiasts and can coordinate observations with SETI.net, you'll want to check Brown's recent work (scroll to the bottom of the page) and contact him for further information. The Wow Signal was detected by Jerry Ehman at the Ohio State University Radio Observatory (known as the Big Ear). The signal, strong enough to elicit Ehman's inscribed comment...

Life seeded throughout the cosmos makes for a satisfying vision, but what are the odds that some kind of panspermia could really happen? Rutgers researchers cast a bit of cold water on the concept recently with data showing what happens to DNA from microbes frozen for millions of years in Antarctic ice. The upshot: Radiation bombardment in the interstellar depths makes survival unlikely. That makes the Fred Hoyle-style delivery of life via cometary bombardment look improbable. Antartica makes a good testbed for such studies because the polar regions receive more cosmic radiation than anywhere else on the planet, as well as containing its oldest ices. The DNA in the five samples studied by the research team showed marked decline after 1.1 million years. Rutgers' Kay Bidle notes that "There is still DNA left after 1.1 million years. But 1.1 million years is the 'half-life' - that is, every 1.1 million years, the DNA gets chopped in half." Bidle's team doesn't completely rule out life...

George Dvorsky's ongoing series on the Fermi Paradox, which appears on his Sentient Developments site, is drawn from a recent conference presentation about the implications of Fermi's question. 'Where are they?' indeed, and what factors could explain our inability to find other sentient life forms? Two parts have already run, and I commend them to you. Dvorsky presents a thorough backgrounder on why the 'great silence' is puzzling, and goes on to discuss the things we can be sure that advanced extraterrestrial intelligences do not do. This by way of examining assumptions that may flag wrong directions in our thinking. The first of these statements is interesting: "Advanced civilizations do not advertise their presence to the local community or engage in active efforts to contact." At least, we might say, in any ways that we've so far been able to determine, and it should be fairly straightforward for an alien species that does want to make itself known to us to manage the feat....

Theories that explain Earthly cataclysms through astronomy are always fascinating. The notion that a dwarf star dubbed 'Nemesis' orbits the Sun and occasionally stirs up cometary debris in the Oort Cloud emerged in the 1980s, published by two independent teams, one of which included Richard Muller. A UC-Berkeley physicist, Muller has since given up on Nemesis, but he's still looking for the cause of what he sees as a 62-million year cycle (plus or minus 3 million years) in mass extinction events. Berkeley's James Kirchner, quoted in this 2005 story on Muller's work, thinks the evidence Muller and graduate student Robert Rohde have assembled on such extinction cycles "simply jumps out of the data." Says Kirchner: "Their discovery is exciting, it's unexpected and it's unexplained. Everyone and his brother will be proposing an explanation -- and eventually, at least one or two will turn out to be right while all the others will be wrong." Muller and Rohde used a huge fossil database of...

I'm glad to see Universe Today's review of Michael Michaud's new book Contact with Alien Civilizations: Our Hopes and Fears about Encountering Extraterrestrials (Springer, 2006), since I haven't gotten to it yet despite a promise early in the year. Those hoping for a thorough analysis of the Drake Equation are in luck, since Michaud evidently tweaks every parameter to see what happens as a result. Many of the issues raised here are things we've kicked around on Centauri Dreams, as is apparent in this excerpt from the review: Are we alone; does the universe revolve around our species; and, is everything in existence for the use of humans? As well, should humans be trying to contact aliens; with what urgency should we start populating outer space; and, how should we react to alien contact? As an example, what would we do if it came to our attention tomorrow that aliens were colonizing Mars? These questions about our actions, our purpose and ourselves serve hopefully, to make the reader...

UK science minister Malcolm Wicks met yesterday with leading British astronomers in a London gathering whose subject was life in the universe. The researchers, drawn from UK universities and research institutes, proved quite optimistic about the chances of intelligent life elsewhere. An article in this morning's Guardian quotes Glenn White, head of astrophysics at the Open University: "You can be pretty sure that if there's life out there, we've a good chance of being able to say so." White's optimism doubtless stems from his work on the Darwin project. The mission, scheduled for a 2015 launch, will deploy a set of telescopes to look for terrestrial worlds around other stars. And although the technology is still in the development stage, the hope is that Darwin's capabilities will extend to conducting spectral analyses on the most interesting planets it finds. That makes detecting biomarkers like large amounts of oxygen along with methane or nitrous oxide a real possibility. Of the...

The early Earth presents us with a conundrum. 3.75 billion years ago, the Sun is thought to have been 25 percent fainter than it is today. Yet liquid water existed on Earth's surface instead of the ice we would expect. How? The answer may be carbon dioxide in the atmosphere, a conclusion drawn from work on ancient rocks in northern Quebec. Says Stephen Mojzsis (University of Colorado at Boulder), "We now have direct evidence that Earth's atmosphere was loaded with CO2 early in its history, which probably kept the planet from freezing and going the way of Mars." The rocks studied by Mojzsis and team show the presence of iron carbonates that are thought to have precipitated from oceans of that distant era. And they could only have formed in an atmosphere that contained CO2 levels far higher than we see today. Thus we witness carbon dioxide's role as a climatic thermostat, raising Earth's temperatures by holding in the weaker heat provided by the Sun. The area of Hudson's Bay under...