How big can an insect get? One night a few years back, I opened the door onto our patio to let the dogs out and an enormous flying, buzzing thing came through the door. When I say 'enormous,' I simply mean it was big enough to startle both dogs enough that they ran upstairs, causing me to grab for a flyswatter as it flitted and hummed around the room. I lost sight of it and suddenly all was silent. Our cat had sprung, and the bug was quickly dispatched. We dubbed it 'Mothra' and added it to our dog lore. After all, where were our Border Collie and Sheltie when we needed them? Peering down at us from the upstairs landing, while the cat did the dirty work. 'Mothra' was probably no more than an inch long -- he was noisier than he was big. But there was a time when 'enormous' really meant something. Meganeura is a genus of insects dating to the Carboniferous period when creatures related to our own familiar dragonfly boasted wingspans of two feet or more. Meganeura monyi is considered...

by James Benford We recently looked at a paper by Duncan Forgan and Robert Nichol on the question of detecting extraneous emissions from an extraterrestrial civilization using technology like the Square Kilometer Array. James Benford (Microwave Sciences) has some thoughts on the issue growing out of his own work with brother Gregory on interstellar beacons and SETI reception in general. No one has put the question of interstellar beacons to tighter scrutiny than the Benfords, with particular regard to bringing the SETI discussion, as Jim puts it, "onto a quantitative basis, as opposed to rampant speculation, as is typical of the playing-tennis-without-a-net approach taken previously." The Benfords' work on interstellar beacons appears this month in Astrobiology. I give full citations at the end of this post. The Forgan & Nichol paper on detection of leakage radiation does neglect our continuing use of microwave beams not only for radar, but also for likely future beaming of power for...

Take a look at the frequency range of our SETI searches and you'll see that we are probing into new territory. Project Phoenix, which ran from 1995 to 2004, used radio telescopes at Arecibo, Parkes (NSW, Australia) and Green Bank (WV, USA), working in a frequency range of 1.2 to 3 GHz. The BETA project used a 26-meter radio telescope to examine the so-called 'waterhole' frequencies between 1400 and 1720 MHz, which seemed a likely place to look for an extraterrestrial beacon because this range covers an unusually quiet band of the electromagnetic spectrum between the hydrogen spectral line and the strongest hydroxyl line. With the Allen Telescope Array coming online, we can look forward to a search of 250,000 stars in the 'waterhole' region, but new facilities like LOFAR (Low-Frequency Array) are pushing into the megahertz area in pursuit not only of SETI but also astrophysical studies of the early universe. LOFAR makes me think back to my shortwave radio days, tuning around these...

We often speak in these pages about extinction events, and cite such examples as the Cretaceous-Tertiary event some 65.5 million years ago, when the mass extinction of dinosaurs and numerous animal and plant species occurred. Whether caused by an incoming asteroid or comet or through a series of catastrophes including volcanic eruptions (the Deccan traps), the K-T event is the classic reminder of the perils that confront life. But perhaps the largest extinction event of all was the so-called 'oxygen catastrophe,' an environmental change that caused oxygen to become widely available in the atmosphere and shallow ocean water. The oxygen catastrophe occurred around 2.4 billion years ago and doomed the bulk of Earth's anaerobic inhabitants. Astrobiologists are fascinated with how life adapts to changing environments, so we'd like to learn much more about how these events proceeded. Now comes news of fossils in black shale formations in Africa that are apparently 200 million years older...

Are planets common around brown dwarfs? We aren't yet in a position to say, but the question is intriguing because some models suggest that the number of brown dwarfs is comparable to the number of low-mass main sequence stars. That would mean the objects -- 'failed' stars whose masses are below the limit needed to sustain stable hydrogen fusion -- could be as plentiful as the M-dwarfs that far outnumber any other type of star in the galaxy. If planets form around brown dwarfs, then we have to add them to our list of possible abodes for life. Evidence for Brown Dwarf Planet Formation But first, to the planet question. We can find suggestive analogs to planet formation around brown dwarfs in nearby space. The star Gl 876, some fifteen light years away, is not a brown dwarf, but this M-dwarf is only 1.24 percent as luminous as the Sun, with most of its energy being released at infrared wavelengths. We now know that at least three planets, two of them gas giants similar to Jupiter,...

Long-term thinking means planning for the consequences of things that are beyond our current capacity. What happens on the farside of the Moon is a case in point. Getting humans back to the Moon is going to happen sooner or later, and one day we will have bases there, as well as a human or robotic presence at the L4 and L5 Lagrangian points of the Earth-Moon system. That means an ever growing blanket of electromagnetic radiation from our various activities. At the same time, we want to protect the farside, which is ideal for future radio telescope or phased array detectors. What to do? Italian physicist Claudio Maccone has brought this issue to Vienna, speaking before the United Nations Committee on the Peaceful Uses of Outer Space. Maccone is proposing a radio-quiet zone on the farside that will guarantee radio astronomy and SETI a defined area in which human radio interference is impossible. It's an idea with a pedigree, going back to 1994, when the French radio astronomer Jean...

Is there a 'Galactic Club' of civilizations to which our species might one day deserve admission? If so, the club's members are being mighty quiet about their existence. But David Schwartzman (Howard University) thinks it might be out there. In that case, he finds three possible explanations for the 'Great Silence,' our failure to detect any signs of extraterrestrial intelligence in the last fifty years. He rejects the first, the notion that we are alone in the galaxy -- life is, in his view, all but inevitable in the universe, and he's keen on the idea of high levels of intelligence developing on many worlds, as he tells us in this article in Astrobiology Magazine: I have argued that encephalization - larger brain mass in comparison to body mass -- and the potential for technical civilizations are not very rare results of self-organizing biospheres on Earth-like planets around Sun-like stars. Biotically-mediated climatic cooling creates the opportunity for big-brained multicellular...

Like astrobiology, SETI is a multi-disciplinary effort, one that pulls together our knowledge and speculation about everything from life's origins to the development of planetary systems and the evolution of civilizations. It's remarkable to remember that it was only fifty years ago that Frank Drake launched the enterprise by scanning a 400 kHz window for interstellar radio transmissions. Epsilon Eridani and Tau Ceti, his target stars, gave us no evidence of extraterrestrial life, but we're continuing to refine the tools for detection. The Allen Telescope Array is just one example of the radio telescope equipment being brought to bear. The Low Frequency Array (LOFAR) and the Square Kilometer Array (SKA) will offer new SETI options in a wide range of wavelengths. SKA will cover 70 MHz to 10 GHz, later extending up to 30 GHz, while LOFAR will survey the skies from 10 to 240 MHz. LOFAR is currently being built and will be the most sensitive radio observatory in the world until SKA comes...

Gliese 581 d seems to be emerging as the exoplanet to talk about in terms of possible life, at least for now. You'll recall that the initial furor was all about Gl 581 c, but that world now looks to be more Venus-like than anything else, while Gl 581 d may just skirt the outer region of the habitable zone in this interesting system. Thus Dirk Schulze-Makuch's contention at the recent astrobiology conference in Houston that this 'super Earth,' if it holds life, may have creatures on it that have adapted to the gravity of a planet at least seven times as massive as the Earth. That would probably produce a population that tends to crawl rather than fly, said the Washington State researcher, and we can let our imaginations go to work on the possibilities. As to Gl 581 d itself, its orbit around this red dwarf may place it in the same relative position that Mars is to our Sun, but throw in volcanoes, a magnetic shield and a thick atmosphere with water oceans below and you could have the...

Finding life on a world in the outer Solar System -- think Enceladus or Titan for starters -- would be an extraordinary step forward. Martian microbes, if they exist, might be evidence of contamination, or we might be evidence of ancient contamination from Mars, given the ready exchange of materials between our planets in the last several billion years. But the outer system offers the possibility of discovering life that originated entirely separately from anything we know. The problem is that we're a long way from having built the spacecraft that can make these detections. That's why places like Pitch Lake, on the island of Trinidad, are so useful. Other than the temperature, conditions here are about as close to what we might find on Titan as anything we know. The 114-acre lake is a cauldron of hot asphalt permeated with hydrocarbon gases and carbon dioxide. As you can see in the image below, it's hardly a hospitable-looking place. But this asphalt hell-hole defies expectation. As...

The Stephen Hawking controversy continues to bubble, with discussion on the Larry King show and the appearance of David Brin's essay The Other Kind of Aliens. It's all to the good to get such discussions widely circulated, even if it can be dismaying to find that so many respondents believe the answers about how alien cultures will behave are obvious and can be readily deduced from our own cultural experiences. But maybe that's because this is a new controversy, one that the search for exoplanets is only now bringing to a wider public in any serious way. There is plenty to ponder, and while we debate the nature of alien culture, let's look at something more immediate. The Protocols of SETI Success SETI continues to look for signals of extraterrestrial civilizations. What happens if a signal is actually detected? For the answer, we can look to the SETI Post-Detection Taskgroup, created by the SETI Permanent Study Group of the IAA (International Academy of Astronautics). The...

These are exciting times for planet hunters, with Kepler and CoRoT in the hunt, three ongoing searches for rocky worlds around Centauri A and B, and the continuing WISE mission, which may identify planet-bearing red and brown dwarfs that we haven't spotted yet, not to mention numerous radial-velocity, transit and microlensing projects. But stepping back to get the big picture is a bit sobering. Jean Schneider did that recently in a paper looking at the far future of direct imaging, wondering where we were headed after Kepler and CoRoT. Schneider (Paris Observatory) talks about a 'conceptual or knowledge horizon,' one we've discussed earlier, that limits us to detecting biomarkers and keeps us from going much further than that for centuries. Seeing Alien Life Up Close Why? A short article on Schneider's work in Astrobiology Magazine condenses the paper's argument. Suppose we do discover signs of life on a planet in the habitable zone of a nearby star. Huge space arrays could help...

NASA's teleconference from the Astrobiology Science Conference 2010 in Houston offered some interesting news about the discovery of microscopic fossils in gypsum from a period about six million years ago, when the Mediterranean Sea had all but dried up. Gypsum (calcium sulfate) precipitates out of sea water, and the find has implications for finding life on Mars, as I'll explain in a moment. What gave me a chuckle, though, was that after a discussion between four crack astrobiologists about life's appearance on Earth and the best ways to search for it elsewhere, the first question from reporters was about Stephen Hawking's views on aliens, and whether NASA had a policy on broadcasts to the stars. The answer is clearly no, and NASA's Mary Voytek noted the differences of opinion between the agency's scientists on the issue, prompting Steven Squyres (of Mars rover fame) to note that our signals are already in play in the form of TV broadcasts and planetary radar signals. I'm thinking...

What Stephen Hawking thinks about aliens made news this weekend, and Centauri Dreams readers will know from our past discussions more or less what Hawking has to say. Assuming we come into contact with an extraterrestrial civilization, it is widely assumed that one of two things will happen. Either an alien visit will be devastating, as has all too often happened when cultures with widely different technologies met, or a benign transfer of information will occur, in which case we benefit by our exposure to new science and revolutionary ideas. A Threat to Humanity? Hawking, who has been working on an upcoming program for the Discovery Channel, opts for the former, as this story in TimesOnline notes. Most life elsewhere in the universe, the physicist believes, will be relatively simple, microbial or primitive animals. But there will be exceptions: ...a few life forms could be intelligent and pose a threat. Hawking believes that contact with such a species could be devastating for...

Just as SETI is redefining its parameters, astrobiology has been going through a shift that widens our notion of habitable zones. Not so long ago, the concept seemed simple. Take a Sun-like star and figure out at what distance a planet could maintain liquid water on its surface. Assume, in other words, that the life you're looking for is more or less like what's found on Earth, and therefore needs the same conditions to persist. Now we're finding remote venues like Enceladus that remind us liquid water can turn up in unusual places, and we've parachuted a probe onto a world, Titan, where it's not inconceivable that exotic forms of life can develop. Throw in the possibility that objects as distant as the Kuiper Belt may contain subsurface liquids and what used to be a constrained habitable zone seems to be vast indeed. And perhaps we've already found another living planet, as astrobiologist Dirk Schulze-Makuch tells Lee Billings in a recent interview. Along with David Darling,...

Changing approaches to SETI are getting public attention these days, as witness a new article in The Economist that makes reference to the probable cause of the interest, the publication of Paul Davies' The Eerie Silence (Houghton Mifflin Harcourt, 2010). Sub-titled 'Renewing Our Search for Alien Intelligence,' Davies' book is making accessible to the general public the kind of discussion we've often had in these pages, looking at the question of whether our SETI strategies at radio and optical wavelengths aren't too limited for any chance of success. The Economist is just one sign of the new interest. After all, technologies like spread spectrum encoding are already masking straightforward radio communications, while conventional broadcasting is giving way to such heavy use of fiber-optics that a planet like ours may go dark at radio wavelengths within a relatively short time as civilizations go, and no more than an infinitesimal flicker in cosmological terms. Thus the interest in...

There is enough going on at the Royal Astronomical Society's 2010 meeting to keep us occupied for some time, but I don't want to go any farther without circling back to UGPS 0722-05, an unusually cool brown dwarf now thought to be the seventh closest star to the Sun. The parallax measurements of its distance are still being refined, but the dwarf is currently thought to be some 9.6 light years from Earth, roughly twice the distance of Proxima Centauri. With a temperature between 130 and 230 degrees Celsius, this is the coolest brown dwarf ever observed, its mass ranging somewhere between five and thirty times that of Jupiter. A number of readers sent links to this discovery, for which many thanks, and I note how interest seems to be growing in the idea that a brown dwarf may exist closer to us than the Alpha Centauri stars. Brown dwarfs are now thought to be relatively common in the galaxy, perhaps as common as normal stars, which suggests that missions like WISE may well discover...