Two Stars, Two Systems?

by Administrator on July 2, 2009

Imagine what space exploration would look like if the Sun were a member of a binary system. Suppose we had another star a few hundred AU away, one that had built its own planetary system. The second star, a thousand times brighter than any other star in our night sky, would be an object of obvious interest, its planets visible to our astronomers and reachable targets for early space technology. The question of life on a planet in that star’s habitable zone would be relatively easy to resolve, and the imperative to study that world first-hand would surely drive space science.

Now we learn that a binary system some 1300 light years from Earth may be evolving in a similar direction. Located in the Orion Nebula, a region rich in star-birth, the stars are about a third the mass of the Sun, considerably cooler and redder in color. One is known to be an M2 dwarf, while the other’s spectral type hasn’t been precisely identified because of obscuration by the disk. The stars are 400 AU apart, so that a single orbit around their common center would take 4,500 years. As this news release from the University of Hawaii at Mânoa points out, that’s about the length of recorded human history.

Researchers have been able to study the pair in the extreme infrared, using the Submillimeter Array on Mauna Kea. That adds to earlier Hubble work showing the presence of one of the disks, visible only as a shadow. The Hawaii researchers have now confirmed the existence of the second. Studies of binary protostars in other regions have generally discovered protoplanetary disks (proplyds) around only the primary star, making this binary system, called 253-1536, an intriguing find.

From the just published paper on this work:

The binary proplyd 253-1536 stands out as the first example of two optically visible stars each with sufficient mass to form a Solar System. Their separation, > 440 AU in projection, is large enough that both the evolution of the disks and their prospects for planet formation can be considered independently of each other.

Remember, too, that at least twenty percent of exoplanets found thus far have been in binary star systems. We’ll learn more about how planets form around binaries — and about how the mass ratio of the stars involved contributes toward the result — as we sample more disks. A key issue considered in this paper is the effect of ionizing radiation from nearby massive stars on the viability of emerging circumstellar disks.

The paper is Mann and Williams, “Massive Protoplanetary Disks in Orion beyond the Trapezium Cluster,” in Astrophysical Journal 699 (June 15, 2009), L55-L58 (abstract).

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Of Technological Lifetimes and Survival

by Administrator on July 1, 2009

Is the movement toward ever more sophisticated technology irreversible? If you’ve studied history, the answer is obviously no. Various speculations arise from this — Carl Sagan once opined that without the intervening collapse known as the Dark Ages, we might have seen a Greek civilization exploring near-Earth space a thousand years ago. It’s also likely that no law prevents another collapse into technological and scientific somnolence, perhaps sparked by war, or disease, or economic catastrophe.

This is why I always hedge my bets when asked about timetables for space exploration. How long until we get humans to the outer system? How long until we launch a fast starship? Everyone is in a hurry, but so much depends on whether we keep growing our technology. Nanotechnology, for example, could change everything, but it’s one thing to be using molecular assemblers by the end of the century, and quite another to see the fruition of this work stalled for a millennium by external events.

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In my grad school days as a medievalist, I found myself examining ancient manuscripts, documents assembled during the interregnum between the end of Roman hegemony in Europe and the first stirrings of the European renaissance. Vellum, which is treated sheep or goat skin, proved to be long-lived, and you can go to places like the British Museum or the Háskóli Íslands in Reykjavik and see some of the glories of the Middle Ages, illuminated manuscripts transcribed in a beautiful hand, conveying the art and wisdom of our species (and not coincidentally, rescuing it from oblivion).

Image: Detail of 14th-century manuscript of Dante’s Commedy (MS Trivulziano 1080).

Today the notion of preserving precious documents seems remote, given the speed with which we digitize and multiply things. But therein lies a trap, and it’s helpful to know that Japanese researchers have developed a form of memory that can store data for over a thousand years. After all, conventional hard disks are subject to magnetic influences that can destroy their information within decades. And if you’re relying on optical disks of various kinds, be aware that a lifetime of a century seems profoundly optimistic.

The researchers note, however, that if you keep the humidity at less than two percent, you can use a semiconductor device to keep data intact for a period approximating that between Alaric’s entry into Rome and the writing of Dante’s Divine Comedy. They’re calling this Digital Rosetta Stone (DRS), a nod to the trilingual artifact that opened up our understanding of Egyptian hieroglyphs. The Rosetta Stone was a way of transmitting ideas (in this case, a decree from Ptolemy V) that contained a multilingual key to a long dead form of writing.

I see that the Long Now Foundation has picked up on the DRS work with a useful suggestion: “If someone finds this disk 1,000 years from now, how will they know how to access the information? We think a microetched instruction manual might do very nicely.” Indeed. As we figure out ways to extend the life of our digital artifacts (and in the process, build one key technology for extremely long-duration spaceflight), we have to remember that future researchers may not approach what we leave behind with the assumptions, or tools, needed to decode it.

We don’t know how long technological societies live — this is a key term in the Drake Equation. Hoping for the best means anticipating a future in which downturns, or even collapse, can be followed by resurgence and renewed growth. We sometimes speak in these pages of a planetary backup plan in case of external catastrophe, but we need one as well for self-inflicted emergency, something history tells us our species is prone to inflict upon itself. And while I’m generally an optimist, I feel better knowing that new ways of preserving information are coming online.

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‘Blobs’ Flag Early Galaxy Formation

by Administrator on June 30, 2009

Look back far enough in time (and hence far enough in distance) and you see things that don’t correspond to nearby cosmic objects. The so-called ‘Lyman-alpha blobs’ that astronomers have found associated with young, distant galaxies are a case in point. Huge collections of hydrogen gas (some of them the largest single objects yet found in the universe), they’re bright at optical wavelengths, raising the question of what powers the glow and how they factored into the galaxy formation process.

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New research may be offering an answer. The key is something called ‘feedback,’ a stage in galaxy formation that shows the interplay between galaxies and the intergalactic medium. Here, the cooling of gas within the dark matter halos enshrouding a young galaxy is countered by heating from active galactic nuclei (think supermassive black holes), which helps to enrich intergalactic space and also slow down star formation.

Image: An artist’s representation showing what one of the galaxies inside a blob might look like if viewed at a relatively close distance. The spiral arms of the galaxy are seen in yellow and white. A two-sided outflow powered by the supermassive black hole buried inside the middle of the galaxy is shown in bright yellow, above and below the galaxy. This outflow illuminates and heats gas surrounding the galaxy, enabling this blob to be seen across billions of light years. Credit: CXC/M. Weiss.

The instrument at work here is the Chandra X-ray Observatory, which has pinpointed the effects of supermassive black holes that, even as they grow, are obscured by the dense layers of gas and dust around them. Also implicated as a power source is the contribution of intense star formation found in these regions. The Lyman-alpha blobs found in an area of sky known as SSA22 are produced by galaxies that are ending their era of rapid growth, and now offer us an insight into how galaxies form.

Bret Lehmer (Durham University, UK), a co-author of the paper on this work, explains the process:

“We’re seeing signs that the galaxies and black holes inside these blobs are coming of age and are now pushing back on the infalling gas to prevent further growth. Massive galaxies must go through a stage like this or they would form too many stars and so end up ridiculously large by the present day.”

Thus the radiation and outflows from black holes and bursts of star formation are powerful enough to illuminate the hydrogen gas of the blobs in which they reside. That’s no small feat, considering that these blobs of gas are several hundred thousand light years across. We’re looking at them at a time when the universe was roughly two billion years old. Rather than galaxies in their infancy, we are evidently seeing galaxy formation as it begins to move away from the period of early rapid growth.

Galaxies in their adolescence? SSA22 offers powerful evidence for that belief. That points to a future where, rather than forming stars, the gaseous blobs will contribute to the gas found between the galaxies. This striking stage of galaxy formation, so unlike the mature galaxies we see in later eras, offers clues to the still earlier era when the flow of gas is inwards and the infant galaxy cools as it emits radiation.

The paper is Geach et al., “The Chandra Deep Protocluster Survey: Ly-alpha Blobs are powered by heating, not cooling,” accepted by the Astrophysical Journal and available online. A Chandra X-ray Observatory news release is also available.

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Finding Life in the Ice

by Administrator on June 29, 2009

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.

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Image: I love Iceland, but pushing as far north as Svalbard would really bring out the adventurer in me. Here we see rough seas in the Arctic Ocean with mountains and glaciers in the distance. Credit: NASA/AMASE/Kirsten Fristad.

Here’s Liane Benning (University of Leeds) discussing the procedures under examination:

“For SLIce, we applied the protocol we had developed to take ice cores, process them and analyze them in the field just as would happen on a rover on Mars, and then of course we took them back to the lab and did a much wider range of tests, so we really knew what we had found. There could be microbes living in the ice, but there could also be the dead bodies of microbes that used to live there, and there could be biological molecules that blew in from dust and micrometeorites. We need to identify what we’ve got, so that we know what it’s telling us.”

And if that earlier image didn’t make you think of Mars, at least the non-aqueous part of the image below should. Here’s we’re looking at the Redbeds in Bockfjorden. These are layered sediments in northern Svalbard that may be similar to layered sedimentary deposits on Mars (credit: Kjell Ove Storvick/AMASE).

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An early SLIce result, described at the Goldschmidt2009 geochemistry meeting in Davos last week: The best place to look for microorganisms in ice is in the layers close to the surface. That’s good to know, because a planetary rover is going to be able to sample such environments much more readily than those several meters beneath. Also helpful is the team’s discovery that cleaning the rover’s sample scoop is harder than it looks, leaving dead micro-organisms on it even after it had apparently been sterilized. New procedures have resolved the problem, ensuring we don’t inadvertently ‘discover’ Earth organisms that have found their way along for the ride.

What happens as we move further out in the Solar System? It’s interesting to speculate on the status of microorganisms near the surface in a radiation-withered environment like that of Europa. But as Richard Greenberg has convincingly demonstrated in his book Unmasking Europa (Springer, 2008), the movement of ice on that world should bring material to the surface — search in the right place and life’s remnants may be close at hand. Now all we have to do is find the funding for a Europa lander (which may be harder to do than flying the mission itself), while developing sufficient radiation shielding to make it feasible. Astrobiology offers no shortage of challenges.

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A Cometary Closeup for NExT

by Administrator on June 26, 2009

By Larry Klaes

Apropos of yesterday’s story on the possible cometary origin of the Tunguska Event in 1908, Tau Zero journalist Larry Klaes looks at the NExT (New Exploration of Tempel) mission, which gives us a second crack at observing comet Tempel 1. Ancient artifacts of the early Solar System, comets can tell us much about its earliest days, but as Larry points out, getting data out of the Deep Impact mission proved to be unexpectedly complicated. NExT is a useful re-purposing of an earlier mission that may unlock further cometary secrets when it returns to Tempel 1 in 2011. If a comet did cause Tunguska, here’s hoping such events continue to be rare, but in the meantime, garnering all the information we can about how comets are made is as important for planetary security as it is for the study of Solar System origins.

An Impact to Remember

Late on the Fourth of July in 2005, while fireworks brightened the sky across the United States, another group of American citizens were making another type of explosion millions of miles away on a small alien world, a form of fireworks being done in the name of science. A robotic space probe, aptly named Deep Impact, lobbed a heavy copper ball at an ancient comet called Tempel 1, smashing into its surface and creating a crater over 300 feet across and almost 100 feet deep in the icy crust.

Mission members had hoped to peer into the crater they made with Deep Impact’s camera eyes to study the deeper and therefore older layers of Tempel 1’s surface. However, they were surprised to discover that the debris kicked up from the impact made a very fine dust cloud that hovered over the crater long after Deep Impact had left the vicinity of the comet, heading back into interplanetary space.

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Image: Deep Impact’s impactor collides with Tempel 1. Credit: NASA/JPL-Caltech.

Inventing a New Mission

Meanwhile, another comet probe named Stardust was winding its way back home after successfully collecting particles from an ice ball named Wild 2 over one year earlier. Stardust would return those priceless samples of an alien world to Earth in early 2006 using a small capsule craft. Then Stardust, its primary mission complete, would swing back out into the void, presumably forever.

Thus the dilemma: Deep Impact had not been able to image the crater it made on Tempel 1 as originally planned and could not return to that comet, while Stardust became a still-functioning spacecraft with plenty of onboard fuel, but with nowhere to go. So some clever folks with the US space agency proposed to reroute Stardust to see what its sister vessel had actually done to Tempel 1 and achieve some other important science goals. NASA approved this mission on July 3, 2007 and Stardust was rechristened NExT, which stood for New Exploration of Tempel 1.

Though NExT will not encounter its cometary target until Valentine’s Day in 2011, mission scientists are already hard at work planning every little detail of the space probe’s one shot at Tempel 1 less than two years from now. Scientists from all over the country met at Cornell University on June 8 and 9 to discuss NExT with the astronomy department’s Joe Veverka, who is the Principal Investigator, or PI, for the mission and a veteran of space expeditions throughout the Solar System.

A New View of a Cometary Crater

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One of those who traveled far to be at this meeting was H. Jay Melosh, a professor of planetary science at the University of Arizona at Tucson. A former member of the Deep Impact team, Melosh is a renowned expert on impact cratering and is naturally quite interested to see what that probe did create on the surface of Tempel 1 almost four years ago.

“We want to get there when the crater made by Deep Impact is in view of NExT’s cameras,” says Melosh, who also emphasizes the importance of precisely timing when the robot explorer would fly by the comet. NExT will be moving so fast on its arrival day that the space probe will zip past Tempel 1 in just 20 minutes.

Image: Comet Tempel 1 just ninety seconds before the 2005 impact. The image was taken by the targeting sensor on Deep Impact’s impactor. Credit: NASA/JPL-Caltech/UMD.

Melosh and his team members also want to see how the comet’s surface may have changed both from the Deep Impact probe crash and natural cosmic effects during its five year orbit around the Sun. Although Tempel 1 is a fairly quiet comet compared to some of its more geologically active brethren, professional astronomers from around the globe monitoring Tempel 1 have noted that its 42-hour rotation rate has changed since humans first visited that little world in 2005. Melosh wants to know exactly how fast the comet is spinning on its axis now and when NExT arrives in 2011.

“Comets vent gas all the time,” explains Melosh, “so they have changing rotation rates as a result. Tempel 1 is a low activity comet, but its rotation rate still changed.”

On to Another Battered World

Though Melosh is now a geophysicist at his university’s Lunar and Planetary Lab (LPL), his first college degree from Princeton was in physics. When he attended Caltech in the early 1970s as a graduate student, Melosh became interested in glaciology and Earth science. He also got a chance to participate in the Mariner 10 space mission, the first vessel to encounter the planet Mercury. Melosh became fascinated with impact craters, which are widely found on this smallest of our system’s terrestrial worlds, during that time.

The scientist plans on exploring another battered celestial object in the near future with a mission labeled GRAIL, which stands for Gravity Recovery and Interior Laboratory. Launching the same year that NExT encounters comet Tempel 1, GRAIL consists of two identical craft that will study our Moon’s gravity field in detail both for science and to assist future lunar spacecraft navigating our neighboring world.

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Comet Implicated in Tunguska Blast

by Administrator on June 25, 2009

Back in my flying days, I found myself becoming absorbed with meteorology, enough to wind up teaching the subject in various flight school settings. I was no expert, but looking for clues on flying conditions in the next few hours by studying cloud formation and movement was fascinating. In all that time, the one cloud phenomenon I always wanted to see but never did was the noctilucent cloud, an unusual, lovely formation made up of ice particles that occurs at extremely high altitudes.

‘Noctilucent’ means ‘night-shining,’ and that’s just what these clouds do when they’re illuminated by sunlight from below the horizon. Space Shuttle launches have been found to generate them as the vehicle pumps about 300 metric tons of water vapor into the thermosphere, the layer of atmosphere beginning at about ninety kilometers above the surface, just above the mesosphere. Photographs of such clouds show a unique beauty, though it’s one that might also seem eerie, at least in certain settings.

Noctilucent_clouds_over_saimaa

For just after the huge explosion that occurred in Siberia in 1908 night skies shone brightly for several days across Europe, particularly Britain, fully three thousand miles away. The Tunguska Event leveled 830 square miles of forest land and has been ascribed to various causes, but a new study concludes that the bright skies following the explosion are a clue to the true culprit, a comet. Those Shuttle-induced noctilucent clouds are the key.

Image: Noctilucent clouds over Lake Saimaa in Finland. Credit: Mika Yrjölä.

Michael Kelley (Cornell University), who led this work, likens it to figuring out a 100-year-old murder mystery. Kelley thinks the evidence strongly supports the comet theory. Such a comet would have started to break up at roughly the same altitude as the release of the exhaust plume from the Space Shuttle. Moreover, water particles from launches have been found to travel as far as the polar regions, where they form noctilucent clouds after settling into the mesosphere.

The Shuttle plume, in other words, parallels what we would expect from a comet, but the wild card has been how water vapor could travel large distances without diffusing. We’re talking about moving this material thousands of kilometers, and quickly. Noting that there is no model that would predict this movement, Kelley calls the result “totally new and unexpected physics.”

Such new physics would involve, the researchers believe, so-called ‘two dimensional turbulence’ — counter-rotating atmospheric eddies packed with extreme energy, powerful enough that when the water vapor becomes involved with them, it travels at more than 90 meters per second. The problem is that the structure of winds in the boundary areas between the mesosphere and the thermosphere is not well understood. Noctilucent clouds may be giving us clues to the nature of this tricky region.

The paper is Kelley et al., “Two-dimensional turbulence, space shuttle plume transport in the thermosphere, and a possible relation to the Great Siberian Impact Event,” in press at Geophysical Research Letters. More in this Cornell University news release.

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Enceladus: Riddle of the Plumes

by Administrator on June 24, 2009

Is there really an underground ocean on Enceladus? The Cassini spacecraft’s striking images have created a cottage industry in speculation, with spectacular glimpses of erupting plumes composed of ice and water vapor. This week, however, we get two contrasting views on what all this means. In one, a paper in Nature by a European team led by Frank Postberg (Universität Heidelberg), studies of sodium salts in dust ejected by the Enceladus plumes reveal telltale signs of a salty ocean deep below the surface.

Postberg was working with data from the Cosmic Dust Analyzer (CDA) instrument aboard Cassini, and the results imply a level of sodium chloride that may be as high as that found in Earth’s oceans. The data come from ice grains in Saturn’s E-ring, which is thought to consist largely of material from Enceladus. Thus we seem to be gathering direct evidence for the presence of the hypothesized ocean, which should be salty from long contact with the rocky core.

enceladus_geyser_plumes_pia08386_big

But not so fast. The same issue of Nature delivers a report from Nicholas Schneider (University of Colorado at Boulder), whose own team examined sodium emission in the plumes erupting from Enceladus. Using the 10-meter Keck 1 telescope and the 4-meter Anglo-Australian telescope, the researchers found no sign of sodium emission, a result that suggests alternative solutions to the riddle of the plumes. One possibility is the presence of deep caverns from which water evaporation is slow, or warm ice vaporising into space. “It could even,” says Schneider, “be places where the crust rubs against itself from tidal motions and the friction creates liquid water that would then evaporate into space.”

Image: Geysers near the south pole of Enceladus. Are we seeing evidence of a subsurface ocean, or are there other explanations? Credit: NASA/JPL/Space Science Institute.

Enceladus comes out of this as enigmatic as ever, the existence of its ocean still debated. If there is a reservoir of salty water on the moon, what are the mechanisms regulating the escape of sodium, and how do we account for the sodium salts of the E-ring? More to come, but for now, the CDA paper is Postberg et al., “Sodium salts in E-ring ice grains from an ocean below the surface of Enceladus,” Nature 459 (25 June 2009), pp. 1098-1101 (abstract). The Schneider paper is “No sodium in the vapour plumes of Enceladus,” in the same issue of Nature, pp. 1102-1104 (abstract).

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SETI: A Detectable Neutrino Signal?

by Administrator on June 23, 2009

Somehow I never thought of the IceCube neutrino telescope as a SETI instrument. Deployed in a series of 1,450 to 2,450 meters-deep holes in Antarctica and taking up over a cubic kilometer of ice, IceCube is fine-tuned to detect neutrinos. That makes it a useful tool for studying violent events like galactic collisions and the formation of quasars, providing insights into the early universe. But SETI?

Perhaps, says Zurab Silagadze (Novosibirsk State University), who notes that most SETI work in the past has focused on centimeter wavelength electromagnetic signals. Says Silagadze:

Here we question this old wisdom and argue that the muon collider, certainly in reach of modern day technology… provides a far more unique marker of civilizations like our own [type I in Kardashev’s classification… Muon colliders are accompanied by a very intense and collimated high-energy neutrino beam which can be readily detected even at astronomical distances.

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Image: The IceCube array in the deep ice, with Eiffel Tower suggesting scale. The dark cylinder is the AMANDA detector, incorporated into IceCube. Credit: NSF.

Muons are elementary particles that, like all such particles, have a corresponding antiparticle of opposite charge. Because they have no known substructure, muons and antimuons offer interesting opportunities for a collider. Their advantage over protons is that the effective collision energy is about ten times higher than for proton beams with the same energy. Moreover, muons are much heavier than electrons and produce less synchrotron radiation. You get higher energy levels with a cheaper collider that is shorter in circumference. Here’s a short backgrounder from Physics World on this.

So it makes sense that, if we can get around formidable practical challenges, we’ll eventually want to develop a muon collider. So, presumably, would an extraterrestrial civilization. And indeed, Silagadze discusses the practical uses of a high-energy neutrino beam in, for example, the study of the inner structure of a planet, or the use of collimated neutrino beams for communications. A 1979 paper by Mieczyslaw Subotowicz went so far as to argue that advanced cultures might deliberately choose neutrino channels for interstellar communications to shut out immature emergent civilizations from the ongoing conversation.

For that matter, is it possible that neutrinos could be used to set interstellar time standards? Note the following from Silagadze’s paper, which places these ideas in the context of the Kardashev scale for measuring the growth of technological civilizations:

Neutrino SETI was also proposed earlier with somewhat different perspective… It was suggested that type II (which have captured all of the power from their host star) and type III civilizations, spread throughout the Galaxy, may require interstellar time standards to synchronize their clocks. It is argued that mono-energetic 45.6 GeV neutrino pulses… produced in a futuristic dedicated electron-positron collider of huge luminosity may provide such standards. If there is an extraterrestrial civilization of this type nearer than about 1 kpc using this synchronization method, the associated neutrinos can be detected by terrestrial neutrino telescopes with an effective volume of the order of km3 of water…

IceCube, anyone? The beauty of neutrino SETI is that it can readily run in the background of concurrent neutrino-based astrophysical studies. Thus keeping an eye out for possibly artificial high-energy neutrino signals produced in muon colliders light years away makes a certain degree of sense. Will it succeed? Silagadze quotes Cocconi and Morrison’s classic paper: “The probability of success is difficult to estimate: but if we never search, the chance of success is zero.”

The paper is Silagadze, “SETI and muon collider,” Acta Physica Polonica B39 (2008), pp. 2943-2948 (available online). The paper on neutrino channels for interstellar communications is Subotowicz, “Interstellar Communication by Neutrino Beams,” Acta Astronautica 6 (1979), pp. 213-220 (abstract).

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TESS Mission Fails to Make the Cut

by Administrator on June 22, 2009

NASA has made its choices, and TESS is not one of them. The Transiting Exoplanet Survey Satellite would have used six telescopes to observe the brightest stars in the sky, a remarkable 2.5 million of them, hoping to find more than 1,000 transiting planets ranging in size from Jupiter-mass down to rocky worlds like our own. An entrant in the agency’s Small Explorer program, TESS could have accelerated the time-frame for discovering another habitable world, assuming all went well.

Not that we don’t have Kepler at work on 100,000 distant stars, looking for transits that can give us some solid statistical knowledge of how often terrestrial (and other) planets occur. And, of course, the CoRoT mission is actively in the hunt. But TESS would have complemented both, looking at a wide variety of stars, many of which would have been M-dwarfs. Not long ago I referred to a Greg Laughlin post that noted a 98 percent probability that TESS would locate a potentially habitable transiting planet orbiting a red dwarf within 50 parsecs of the Earth.

Were that the case, the results could have been handed over to the James Webb Space Telescope, scheduled for launch near the end of the putative TESS mission, for further investigation. JWST, so the thinking goes, could then take a spectrum and tell us something about conditions in that planet’s atmosphere. Retrieving data from the atmospheres of such planets is crucial to astrobiology and we’ll get it done one day, but perhaps not as soon as we hoped.

Getting a mission into space is no easy matter in the best of times (see Alan Boss’ The Crowded Universe for vivid proof of this). Consider that the two Small Explorer (SMEX) finalists were chosen from an original 32 submitted in January of 2008. The SMEX missions are capped at $105 million each, excluding the launch vehicle. That cost would depend on the vehicle — the last time I looked, an Atlas V would command $130 million. We’re talking relatively small investment for a solid scientific return, even if that return doesn’t include exoplanetary results on this round.

One of the two proposals now to be developed into full missions is the Interface Region Imaging Spectrograph, which will use a solar telescope and spectrograph to look at the Sun’s chromosphere. The other is the Gravity and Extreme Magnetism SMEX mission, which will measure the polarization of X-rays emitted by neutron stars and stellar-mass black holes, as well as the massive black holes found at the centers of galaxies.

Given that one of NASA’s stated aims with the SMEX program is “…to raise public awareness of NASA’s space science missions through educational and public outreach activities” (see this news release), the agency may have missed an opportunity with TESS. We’re close to the detection, through radial velocity or transit studies, of a terrestrial planet around another star. That’s going to put the study of that planet’s atmosphere for life signs high on everyone’s agenda, including the public’s. From the PR perspective, TESS was a gold-plated winner.

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Brute-Force Engineering and Climate

by Administrator on June 19, 2009

The eruption of Mt. Tambora in Indonesia in 1815 pumped so much sulfur dioxide into the stratosphere that New England farmers found their fields frosted over in July. Climate change, it seems, can be quick and overwhelming, at least on short scales. The eruption of the Mt. Pinatubo in the Philippines in 1991 cooled global temperatures for several years by about half a degree Celsius. Sulfur dioxide works.

So how about this: We send a fleet of airships high into the stratosphere, attached to hoses on the ground that pump 10 kilos of sulfur dioxide every second. The airships then spew this mix into the upper atmosphere, a aerosolized pollutant that, turning the skies Blade Runner red, shields the planet from the Sun’s heat. Call it geo-engineering, an extreme form of human climate manipulation that is the subject of a recent story in The Atlantic.

Into the Anthropocene

Writer Graeme Wood notes that our activities have been transforming the planet for centuries now, leading some to dub our era the ‘anthropocene’ period. Says Wood:

…humans have reshaped about half of the Earth’s surface. We have dictated what plants grow and where. We’ve pocked and deformed the Earth’s crust with mines and wells, and we’ve commandeered a huge fraction of its freshwater supply for our own purposes. What is new is the idea that we might want to deform the Earth intentionally, as a way to engineer the planet either back into its pre-industrial state, or into some improved third state. Large-scale projects that aim to accomplish this… constitute some of the most innovative and dangerous ideas being considered today to combat climate change.

For it turns out that the sulfur dioxide idea is just one among many. Scottish engineer Stephen Salter discusses a strategy to use a fleet of 1500 ships to churn seawater, spraying it high into the clouds to add moisture and make the clouds more reflective. Roger Angel (University of Arizona) proposes a series of huge electromagnetic guns in the upper atmosphere that would launch a Sun-shield made up of millions of Frisbee-sized disks to the L1 Lagrangian point, effectively scattering sunlight.

Freelancing Global Climate Change

The danger here, beside the unintended consequences that could so quickly attend such schemes, is that international cooperation on climate change could quickly be rendered irrelevant. Solutions like sulfur dioxide are cheap enough — $100 billion would be enough, Wood says, to reverse anthropogenic climate change entirely, and it might cost far less — that a single country could take on the challenge itself.

Wood turns to geophysicist Raymond Pierrehumbert (University of Chicago) for thoughts on possible unintended consequences of the sulfur dioxide strategy. The geophysicist reminds him of the Greek legend of Dionysius II, who to make a philosophical point suspended a sword over Damocles’ head from a single hair:

According to Pierrehumbert, sulfur aerosols would cool the planet, but we’d risk calamity the moment we stopped pumping: the aerosols would rain down and years’ worth of accumulated carbon would make temperatures surge. Everything would be fine, in other words, until the hair snapped, and then the world would experience the full force of postponed warming in just a couple of catastrophic years. Pierrehumbert imagines another possibility in which sun-blocking technology works but has unforeseen consequences, such as rapid ozone destruction. If a future generation discovered that a geo-engineering program had such a disastrous side effect, it couldn’t easily shut things down. He notes that sulfur-aerosol injection, like many geo-engineering ideas, would be easy to implement. But if it failed, he says, it would fail horribly. “It’s scary because it actually could be done,” he says. “And it’s like taking aspirin for cancer.”

A Carbon-Cutting Alternative

Cutting carbon emissions seems like a far preferable solution, and it’s one that Freeman Dyson suggested in a geo-engineering strategy he designed as far back as 1977, one that would create forests of trees engineered to be more effective at drawing carbon from the air, trapping the carbon in the topsoil. Other carbon-withdrawing schemes call for creating large towers whose grids would be coated with a chemical solution that could bind carbon-dioxide molecules. That one, by David Keith (University of Calgary), stashes captured carbon deep underground.

Ponder the implications when any one of the 38 people on the planet who have $10 billion or more in private assets could try to reverse climate change single-handedly. There’s one more Fermi solution — technological civilizations run afoul of their own technology as the cost of tackling massive projects drops to the point where individuals or small groups can destroy an ecosystem while attempting to fix it. Is a game-changing technology to fix climate change worse than the problem? Perhaps a more judicious view is that a technological big fix is what Wood calls “…the biggest and most terrifying insurance policy humanity might buy — one that pays out so meagerly, and in such foul currency, that we’d better ensure we never need it.”

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