by Paul Gilster | Jun 16, 2009 | Culture and Society |
Life Beneath the Ice
Three kilometers down in the Greenland ice sheet is what I call an extreme environment. Even so, Penn State researchers have been able to bring a bacterium called Herminiimonas glaciei back to life after a dormancy of 120,000 years in these conditions. The work involved incubating the samples at 2 degrees Celsius for seven months, then at 5 degrees Celsius for a further four and a half, a patient process rewarded by the appearance of the purple-brown bacteria.
Ten to fifty times smaller than E. coli, Herminiimonas glaciei evidently used its size to survive in liquid veins amongst the ice crystals. Jennifer Loveland-Curtze describes the find:
“These extremely cold environments are the best analogues of possible extraterrestrial habitats. The exceptionally low temperatures can preserve cells and nucleic acids for even millions of years. H. glaciei is one of just a handful of officially described ultra-small species and the only one so far from the Greenland ice sheet; studying these bacteria can provide insights into how cells can survive and even grow under extremely harsh conditions, such as temperatures down to -56?C, little oxygen, low nutrients, high pressure and limited space.”
Europa, anyone? Or how about the polar caps of Mars? We can’t rule out microbes evolved from the icy conditions present in such places. And as to longevity, this new find is out-done by the eight-million year-old bacterium found beneath the surface of a glacier in Antarctica (although questions have been raised about possible contamination in that sample). The paper on the Greenland find is Loveland-Curtze et al., “Herminiimonas glaciei sp. nov., a novel ultramicrobacterium from 3042 m deep Greenland glacial ice,” International Journal of Systematic and Evolutionary Microbiology 59 (2009), pp. 1272-1277 (abstract).
A New Look at Space Elevators
The old saying has it that if you can get to low Earth orbit (LEO), you’re halfway to any destination in the Solar System. That makes my interest in Michel van Pelt’s new book rather keen, because the space elevator described here is just the ticket for getting large payloads into space on a continuing basis, the sort of thing we’ll have to do as we build a true system-wide infrastructure for our species. Space Tethers and Space Elevators (Copernicus, 2009) gathers the thoughts of this European Space Agency analyst on the practicality and promise of a technology that seldom seems to get the press it deserves.
But as the technology evolves, we’ll be experimenting with numerous tether concepts less demanding than the elevator, ranging from generating electricity in a magnetosphere to braking and accelerating spacecraft. So-called ‘momentum exchange’ tethers may have a significant role to play as we consider alternatives to chemical rocketry for exploring near-Earth space all the way to Mars. As far as I know, this book is the first full-length popular treatment of the tether concept. More on tethers and elevators as I get into the book (have to finish Alastair Reynolds’ Revelation Space first).
A Carnival Look at Betelgeuse
UC-Berkeley astronomers have noticed that Betelgeuse has lost fifteen percent of its diameter within the last fifteen years. And as Ian O’Neill notes on Space Disco, it took all the resources of the Infrared Spatial Interferometer (ISI) on Mt. Wilson to make such a precise measurement of a star that has undergone no variation in its luminosity. Are we looking at a perfectly normal phenomenon — the star has varied in size in the past — or is the shrinkage itself an illusion, brought about by our observation of a star that is not spherical?
The latter seems reasonable, and O’Neill notes that simulations point to Betelgeuse, which is shrouded by clouds of gas and dust, as a potato-shaped object. But O’Neill’s real point is to attack the ginned up media coverage of the UC-Berkeley news release, which was perhaps triggered by a New Scientist story called Betelgeuse: The incredible shrinking star?, in which UC-Berkeley’s Charles Townes speculated “Maybe there’s some instability in the star and it’s going to collapse or at least go way down in size or blow off some material, but who knows.”
A Fox News story on a potential supernova shot to the front page of Digg. Comments O’Neill: “Everyone loves a supernova. As for the “shrinking star” reports, not so much… This may not have the makings of the next, great doomsday movie plot, but it is an example how definite conclusions (i.e. a supernova) can be made from a fairly benign, yet interesting astronomical ‘mystery.'” O’Neill’s comments are part of the most recent Carnival of Space, now available on the fine Innumerable Worlds site.
by Paul Gilster | Jun 15, 2009 | Astrobiology and SETI |
If we can find a way to double the lifespan of Earth’s biosphere, we’ll have changed the odds for finding extraterrestrial civilizations. After all, the amount of time an advanced culture can exist is one of the variables in the famous Drake equation, which estimates how many intelligent civilizations there are in the Milky Way. Lengthen potential habitability and you give any civilization that much more chance to spread into the cosmos.
Thus recent work out of Caltech intrigues us in several directions. Joseph Kirschvink and colleagues look at effects that could add a billion years on to our planet’s projected habitability. Consider: Earth took some four billion years to develop intelligent life, leaving us about a billion before our planet becomes uninhabitable. That result would be caused by a brighter and hotter Sun, the loss of carbon dioxide in the atmosphere through the weathering of rocks, and the eventual evaporation of water from the oceans, leaving nothing alive.
Reducing the amount of carbon dioxide in the atmosphere helps to ease the warming effect, and indeed, according to this Caltech news release, the pressure of carbon dioxide in the atmosphere has dropped 2,000-fold over the past 3.5 billion years, with man’s industrial activities serving to offset only a fraction of the decrease. Kirschvink believes “…we’re nearing the point where there’s not enough carbon dioxide left to regulate temperatures following the same procedures.” That points to a hot and uninhabitable future in a billion years or so.
Reducing atmospheric pressure could be a way around this outcome. The scientists say that removing massive amounts of molecular nitrogen, which already makes up 78 percent of the atmosphere, would allow us to regulate surface temperatures, ensuring that carbon dioxide will remain in the atmosphere and adding 1.3 billion years to Earth’s habitable life. It sounds like a science fictional solution relying on some vast future technology to re-tune the atmosphere, but Kirschvink’s team thinks the process may actually happen naturally.
After all, nitrogen is incorporated into the cells of growing organisms and gradually removed from the atmosphere as they die. Nitrogen reduction may be an ongoing process, suggesting that Earth’s atmospheric pressure may be lower now than in earlier epochs. One way to examine this, say the scientists, would be to study gas bubbles in ancient lavas, which could provide a reading on the change in atmospheric pressure over time.
Could exoplanetary studies give us clues to our own future? Grad student Kaveh Pahlevan, who worked with Kirschvink on this paper, sees a strong possibility:
“Hopefully, in the future we will not only detect earth-like planets around other stars but learn something about their atmospheres and the ambient pressures. And if it turns out that older planets tend to have thinner atmospheres, it would be an indication that this process has some universality.”
What would we do with an additional billion or so years of life? If technological civilizations are not in fact self-destructive, longer lifespans should give them a much greater chance of finding each other. The paper is Li et al., “Atmospheric Pressure as a Natural Regulator of the Climate of a Terrestrial Planet with Biosphere,” Proceedings of the National Academy of Sciences, published online June 1, 2009 (abstract).
by Paul Gilster | Jun 13, 2009 | Culture and Society |
The bet between Tibor Pacher and myself continues to draw emails, proving that my friend Tibor was right when he saw an interstellar wager as a teaching opportunity. I still maintain that an interstellar mission will not be launched anywhere near as early as 2025, but Tibor does have his advocates, as you can see on the Long Bets site. Moreover, it’s been useful to plug in distances and velocities for a 2000-year mission to a place like Proxima Centauri when I speak to audiences about how large the distance between the stars really is. 2000 years is a long time, but we’re still talking 650 kilometers per second, and just 20 years to the Oort Cloud!
And as a guy who used to build model airplanes back in my youth, first in plastic and then from balsa wood (wonderful memories of working with kits of World War I and II aircraft from Guillow), I can relate to Tibor’s latest venture. MiniSpaceWorld is an attempt to create, at a European site still to be determined, a wide-ranging exhibit covering the state of the art in rocketry and pointing toward a future that encompasses missions to extrasolar planets. Tibor’s inspiration for this was the amazing Miniatur Wunderland in Hamburg, an exhibition that may be the most spectacular gathering of model railway talent ever assembled in a single place.
With content ranging from the experiments of Galileo up to existing space installations worldwide and extending to showcase potential exoplanetary environments, MiniSpaceWorld aims to cover the gamut of space exploration, all in a miniaturized format that can pack an enormous amount of material into a small space, roughly 3500 square meters in two levels, with a potential for growth. The design contest soliciting ideas in all categories can be accessed through the MSW site, where details of contest entries and the format to be used are also provided. A jury including Tau Zero’s Marc Millis will judge the winners, with an award ceremony to be held in December in Budapest, organized in conjunction with Galaktika, the award-winning European science fiction magazine.
Image: One aspect of MiniSpaceWorld will be modeling of existing space installations around the world. Credit: Ferenc Gál.
The contest is open now and will run until October 15, a chance to contribute to a scale model world for space exploration that, Tibor hopes, will help to promote public interest and funding for future ventures. It’s an ambitious project that deserves support. I notice that the Miniatur Wunderland venue in Hamburg draws 700,000 visitors a year, a demonstration that small scale modeling can grow into a significant opportunity for education over time. Building the intellectual framework now — especially for the kids — can help us down the road once we emerge into a time of more robust funding for deep space missions.
by Paul Gilster | Jun 12, 2009 | Astrobiology and SETI |
Among the most interesting of the future missions now being weighed by NASA, TESS (the Transiting Exoplanet Survey Satellite) would help scientists using the James Webb Space Telescope know where to look for Earth-like planets around nearby stars. While the invaluable Kepler mission scans 100,000 distant stars, hoping to gain statistics on Earth-sized exoplanets, TESS would have a different aim, looking for transiting terrestrial worlds around only the brightest stars. A 2012 launch is possible if the mission is approved.
Here’s Greg Laughlin (UC-Santa Cruz) on TESS’ possibilities:
TESS… provides the cheapest, shortest, and most direct path to the actual characterization of a potentially habitable planet. Included in the 2.5 million brightest stars are a substantial number of M dwarfs. Detailed Monte-Carlo simulations indicate that there’s a 98% probability that TESS will locate a potentially habitable transiting terrestrial planet orbiting a red dwarf lying closer than 50 parsecs. When this planet is found, JWST (which will launch near the end of TESS’s two year mission) can take its spectrum and obtain resolved measurements of molecular absorption in the atmosphere.
And note this:
If TESS is selected for flight, we’re literally just five years away from probing the atmospheres of transiting planets in the habitable zone.
You can see how these missions could work together. Roughly one in every 200 Earth-like planets would be available through the transit method, according to Oliver Morton in Found in Transit, a guest column that ran Wednesday in the New York Times. We need to know which nearby stars offer transits because we’d like to look at planetary atmospheres when backlit by the star. A new paper in Nature goes a long way toward showing how effective this method can be at revealing the existence of life.
The work comes from the Instituto de Astrofisica de Canarias (IAC), where scientists thought to study the phenomenon of starlight passing through a planetary atmosphere close to home. This so-called transmission spectrum can be observed from Earth’s surface by examining light reflected from the Moon during a lunar eclipse. This news release claims the result is the first measurement of the Earth’s transmission spectrum, and it’s a revealing one at that.
Image: The moon during a lunar eclipse. Earth’s transmission spectrum measured during such an eclipse shows strong signs of life. Credit:Daniel Lopez, IAC.
IAC’s Enric Pallé notes that the spectrum showed unexpectedly strong life signs, including methane and oxygen carrying a recognizable signature. Moreover, as theory suggested, light passing through a planetary atmosphere seems to carry much clearer data on the atmosphere’s chemistry than light reflected directly off the surface of the planet. Says Pallé:
“Now we know what the transmission spectrum of a inhabited planet looks like, we have a much better idea of how to find and recognize Earth-like planets outside our solar system where life may be thriving. The information in this spectrum shows us that this is a very effective way to gather information about the biological processes that may be taking place on a planet.”
Methane and oxygen, as Morton notes in his essay, have been studied since the 1960s in terms of their stability. James Lovelock, the English chemist who later developed the Gaia theory of the Earth as a single organism, was the first to realize that a spectroscopic analysis of chemicals in a planetary atmosphere could tell us whether life is present.
The key is instability, meaning that the oxygen and methane we find in Earth’s atmosphere react with each other. It takes life to keep these reactions happening. Without it, the atmosphere would show an unmistakable stability. But we can pick up chemical disequilibrium in an atmosphere readily, assuming the IAC work is on target, and that tells us how productive TESS could be as a finder mission for the JWST, which could turn its formidable resources loose on making the relevant observations.
Some other interesting notes from Morton’s essay:
- Little of a star’s light actually hits any of its planets. Perhaps as little as half a billionth of the Sun’s output actually strikes the Earth.
- A telescope six times the size of the JWST (which itself will be the largest space telescope every launched when it sets out in 2014) would receive only one photon every ten seconds when looking at a planet sixty light years away.
No wonder we need transits, which in the case of an Earth-sized planet in front of a Sun-sized star, diminish the star’s light by about one twelve-thousandth. A tiny effect, but more than enough to measure and analyze. The paper, a significant one, is Pallé et al., “Earth’s transmission spectrum from lunar eclipse observations,” Nature 459 (11 June 2009), pp. 814-816 (abstract).
by Paul Gilster | Jun 11, 2009 | Exoplanetary Science |
Gravitational microlensing has been actively employed in the search for MACHOs (Massive Astrophysical Compact Halo Objects) in the galactic halo, although with ambiguous results. The idea here is to find large, dark objects by detecting the microlensing effects they produce on stars behind them. While these dark matter studies have looked toward the Large Magellanic Cloud, we are using the same technique elsewhere in the planet hunt, finding that exoplanets can magnify the light of stars behind them in the galactic bulge, producing a clear detection.
Remember, for this kind of work, you want a dense background field of stars because the alignment needed for microlensing is obviously rare. The Magellanics are ideal, as is the galactic bulge, and so, for that matter, is M31, the Andromeda galaxy.
And if our early exoplanet work, relying on radial velocity and transit methods, has naturally produced large planets in the Jupiter class, microlensing can be quite effective at smaller scales. Now a new paper examines yet another benefit of the technique, that it works better at large distances from the source star, giving us the chance to detect planetary systems not only here in the Milky Way but in other galaxies as well.
The paper, by Gabriele Ingrosso (INFN, Italy) and colleagues, notes that at these distances, only giant stars with large radii can produce detectable microlensing events. The work is tricky because the source stars cannot be resolved by ground-based telescopes. ‘Pixel lensing’ is the name used for gravitational microlensing in such situations, and applied successfully, it can tell us much about the distribution of matter in a galaxy like M31, showing us its own dark halo objects as they cause microlensing of starlight in the background disk.
Image: The M31 galaxy may be offering up evidence of planets in its halo, if pixel lensing data can be correctly interpreted. Credit: Space Telescope Science Institute.
In fact, there have been a small number of microlensing events already detected towards M31 by two different collaborations, and planets may well be in the mix. Note this from the paper, which explains how exoplanet discoveries tie in with ongoing work on compact dark matter objects in the galactic halo (I’ve deleted internal references for brevity):
…new observational campaigns towards M31 have been undertaken… and hopefully a few planets might be detected in the future, providing a better statistics on the masses and orbital radii of extrasolar planets. It is in fact expected, and supported by observations and numerical simulations, that almost any star has at least a planet orbiting around it… In other words… the rate of single lens events towards M31 may suffer of a strong contamination of binary lensing events, most of which are expected to be due to extrasolar planets.
Planets in Andromeda? The mind boggles at the thought of detecting such, not that we don’t assume they’re present, but who would have believed our technology capable of such a reach? One anomalous pixel-lensing event has already turned up, possibly indicating a planet some six times as massive as Jupiter. It’s too early to claim a planet in Andromeda’s halo, but the candidate event labeled PA-99-N2 looks suspiciously like one, and pixel lensing itself seems destined to flag more.
The paper is Ingrosso et al., “Pixel-lensing as a way to detect extrasolar planets in M31,” accepted for publication in Monthly Notices of the Royal Astronomical Society and available online.
