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Life Under Infrared Skies

So far we know of only one place in the cosmos that has life, our own Earth. That makes the study of interesting organisms, and in particular the so-called ‘extremophiles’ that stretch our understanding of livable habitats, a key part of astrobiology. Finding an organism living around a deep-water vent on the ocean floor doesn’t prove life exists in such environments on other worlds, but by understanding the limits of the possible, we’re learning more about where and how to look.

And sometimes we find unusual life forms in seemingly benign places like Australia’s Great Barrier Reef, which brings us to Acaryochloris marina. That tongue twister identifies a bacterium that is unusual because it uses a rare type of chlorophyll — chlorophyll d — to take advantage of near infrared long wavelength light. Acaryochloris marina is actually a cyanobacterium, meaning a bacterium that use photosynthesis to derive its energy. Its huge genome (8.3 million base pairs) has now been sequenced for the first time, with interesting implications for plant research and, conceivably, astrobiology. Thanks to Vincenzo Liguori for sending a link to Astrobiology Magazine‘s coverage of this work.

Jeffrey Touchman (Arizona State), lead author of the paper in question, sees applications in various forms of plant research:

“Chlorophyll d harvests light from a spectrum of light that few other organisms can, and that enables this organism to carve out its own special niche in the environment to pick up far-red light. The agricultural implications could be significant. One could imagine the transfer of this biochemical mechanism to other plants where they could then use a wider range of the light spectrum and become sort of ‘plant powerhouses,’ deriving increased energy by employing this new photosynthetic pigment.”

Space applications? Productive crops for space stations are one possibility. But looking outward, the gaze is inevitably drawn to the 75 to 80 percent of stars in the Milky Way that are M-dwarfs. Speculation about habitable planets around these stars heated up with the controversy over Gliese 581’s planets, but the broader issue addressed by finds like this is that Earth life adapted to the near infrared may be showing us the directions life could take in other exotic environments. After all, most of the radiation an M-dwarf emits is in the infrared.

Just how chlorophyll d is formed depends upon an enzyme that causes the needed chemical changes to distinguish it from the more common chlorophyll a and b, among other types of chlorophyll. The research team, working at Arizona State and Washington University (St. Louis) will test to see if organisms can be induced to produce chlorophyll d with candidate genes inserted. If so, genetically altered plants could result that take advantage of a wider range of available light. In the meanwhile, our ideas about habitable zones get another nudge.

It would be tricky to come up with a form of life, even on a planet circling a red dwarf, more unusual than Acaryochloris marina. The cyanobacterium lives in symbiosis with the sea squirt, a marine animal something like a sponge that attaches itself to rocks below the water’s surface. Our cyanobacterium lives beneath the sea squirt, absorbing its needed infrared through.the creature’s tissues. Now that’s exotic!

The paper is Touchman et al., “Niche adaptation and genome expansion in the chlorophyll d-producing cyanobacterium Acaryochloris marina,” Proceedings of the National Academy of Sciences Vol. 105, No. 6 (12 February, 2008), 2005-2010 (abstract).

Comments on this entry are closed.

  • Kevin A. February 13, 2008, 15:42

    Huge agricultural space stations orbiting M-dwarfs to grow food for humans as they spread through the galaxy…. hm. Neat idea.

  • andy February 13, 2008, 16:06

    I wonder how difficult it would be to set up a light source that mimics the spectrum of an M dwarf, and attempt to grow various kinds of organisms under that light source. Might be an interesting experiment to try.

  • Colin Weaver February 13, 2008, 17:50

    Why stop at M class? Karl Schroeder touches on the subject of infrared adapted plants in his novel “Permanence”, in which an Earth size world orbiting what I take to be a T-class Brown Dwarf sustains infrared adapted plants genetically engineered from Earth life.

  • Administrator February 13, 2008, 19:15

    Colin, I agree. Permanence is quite a good read, and should be on the agenda of anyone with an interest in life around diminutive stars.

  • James M. Essig February 14, 2008, 9:16

    Hi Folks;

    Who knows what life forms we will find around other low temperature planets around low luminosity stars such as red dwarfs. Perhaps material such as methane, ethane, ethylene, and the like which are gaseous at STP could be the liquid backbone of organisms thriving at temperatures between 100 K and 150 K.

    Also, some planets around Red Dwarfs might have green house gases in their atmospheres sufficient to permit temperate climate organisms to evolve and flourish, perhaps even having temperatures simmilar to Earth’s ecosystems.

    In extreme cases, I have read of conjectured lifeforms that may have arisen from transient nuclear-strength-like (although not quite as strong as nuclear bonds) atomic bondings of and in the evolution and thermodynamic activities among the superdense atomic states matter such as may exist on the very outer surface of nuetron stars. These organisms accordingly would probably not be able to live at locations inside or above the surface of the neutron star because they would have evolved to exists in superdense atomic states which may only exist at the very surface of the star. If they were to leave the star, they would simply decompress and explode, if they where to travel into the star, they would be crushed into formless nuetronium.


    Your Friend Jim

  • ljk March 23, 2008, 19:14

    Scientists envision aliens who are strangely familiar


    Computer-generated climate models like those used on Earth are among the tools used in imagining the habitability of moons and other planets:

    • The Montreal exhibit’s imaginary Aurelia planet orbits a “red dwarf” star, dimmer than the sun, but close. Number-crunching suggests “a planet like Aurelia could end up with at atmosphere quite like Earth’s” – habitable, as water and carbon “cycle from the planet to its atmosphere and back again.”

    • Climate modelling for the exhibit’s Blue Moon, which orbits a giant gas ball, yielded a tropical carbon-dioxide-and-oxygen-rich atmosphere, with a greenhouse effect causing violent rainstorms.


    Creatures will look weird all right, say experts who have imagined some for a new exhibit. But inside they could turn out to be surprisingly like us

    Mar 23, 2008 04:30 AM

    Andrew Chung

    Staff Reporter

    If the prototypical alien is the gruesome monster that a crew of highly unfortunate humans found in a remote space outpost in the film Aliens, with Sigourney Weaver, you might say our future seems bleak.

    The aliens in that film – actually a series that began with Alien in 1979 – are terrifying and bloodthirsty, salivating from their two sets of jaws, bent solely on turning human bodies into wombs from which baby aliens violently burst.

    But come on, just how realistic – biologically speaking – is an alien whose blood is acidic enough to eat through several decks of a spaceship?

    Or what about the Martians in H.G. Wells’s The War of the Worlds, hideous blobs with Gorgon-like tentacles descending from their quivering mouths, pipetting victims’ blood into their own veins?

    Or, for that matter, the blob in the Steve McQueen movie of the same name?

    There has been no shortage of alien depictions in literature, comic books and film.

    But now scientists are putting some extra thought into the idea of aliens. They’ve come up with some interesting results.

    An exhibition, set to open April 10 at the Montreal Science Centre, intends to add scientific rigour to a subject heretofore solely the domain of human imagination.

    Using the expertise of a number of renowned scientists, the exhibition presents ideas on what aliens might look like, taking into consideration biology, astronomy, and the laws of physics and chemistry.

    “It’s fiction, yes, but it’s science-based science fiction,” says Louise Julie Bertrand, the head of exhibitions at the Centre. Such an exercise, she adds, will appeal to both kids and adults. “People are often attracted to the bizarre and intriguing and weird.”

    The stars of the exhibition are these alien forms envisioned by the scientists to fit the specific characteristics of two “planets,” such as carbon content, the temperature, the type of atmosphere.

    “It was a real attempt to come up with creatures, that, although fanciful, are plausible,” says Michael Meyer, an astrobiologist and the lead scientist for NASA’s Mars Exploration Program.

    The exhibit opens with depictions that authors and filmmakers have dreamed up. A common theme is how aliens are viewed as the other, just as witches – and even Communists – have been.

    “Through the ages, they have always been something we feared,” Bertrand says. “Dragons, witches, aliens, this is a recurring (theme) through history. The stranger, the person different from us, this is who we’ll focus our fears on.”

    Full article here:


  • ljk March 31, 2008, 13:25

    Review: Beyond UFOs

    To many, life on other worlds means aliens and flying saucers. Jeff
    Foust reviews a book that tries to move beyond those perceptions to
    provide a solid scientific review of astrobiology.


  • ljk April 11, 2008, 11:24

    The Color of Plants on Other Worlds

    On other worlds, plants could be red, blue, even black

    By Nancy Y. Kiang

    RED EARTH, GREEN EARTH, BLUE EARTH: Type M stars (red dwarfs) are feeble, so plants on an orbiting Earth-like world might need to be black to absorb all the available light (first panel). Young M stars fry planetary surfaces with ultra?violet flares, so any organisms must be aquatic (second). Our sun is type G (third). Around F stars, plants might get too much light and need to reflect much of it (fourth).

    Key Concepts

    What color will alien plants be? The question matters scientifically because the surface color of a planet can reveal whether anything lives there—specifically, whether organisms collect energy from the parent star by the process of photosynthesis.

    Photosynthesis is adapted to the spectrum of light that reaches organisms. This spectrum is the result of the parent star’s radiation spectrum, combined with the filtering effects of the planet’s atmosphere and, for aquatic creatures, of liquid water.

    Light of any color from deep violet through the near-infrared could power photosynthesis. Around stars hotter and bluer than our sun, plants would tend to absorb blue light and could look green to yellow to red. Around cooler stars such as red dwarfs, planets receive less visible light, so plants might try to absorb as much of it as possible, making them look black.

    The prospect of finding extraterrestrial life is no longer the domain of science fiction or UFO hunters. Rather than waiting for aliens to come to us, we are looking for them. We may not find technologically advanced civilizations, but we can look for the physical and chemical signs of fundamental life processes: “biosignatures.” Beyond the solar system, astronomers have discovered more than 200 worlds orbiting other stars, so-called extrasolar planets. Although we have not been able to tell whether these planets harbor life, it is only a matter of time now. Last July astronomers confirmed the presence of water vapor on an extrasolar planet by observing the passage of starlight through the planet’s atmosphere. The world’s space agencies are now developing telescopes that will search for signs of life on Earth-size planets by observing the planets’ light spectra.

    Photosynthesis, in particular, could produce very conspicuous biosignatures. How plausible is it for photosynthesis to arise on another planet? Very. On Earth, the process is so successful that it is the foundation for nearly all life. Although some organisms live off the heat and methane of oceanic hydrothermal vents, the rich ecosystems on the planet’s surface all depend on sunlight.

    Full article online here:


  • ljk May 2, 2008, 13:35

    Non-Carbon Species: Will We Overlook Extra-terrestrial Life?

    A Galaxy Classic

    Carbon is great molecular glue—there’s not doubt about it. Just add water and you’ve got life. Well, maybe it’s not quite that simple, but carbon and water do seem to be a winning combo, at least on planet Earth. That may be why we’ve been limiting ourselves in our search for . The carbon/water combo has worked so well for our own conditions, that we simply can’t imagine anything else supporting life.

    Currently, our search for extra-terrestrial life forms has been focused on planets similar to ours. The perplexing idea exists, however, that what would be death to us on Earth, may be life to other beings. What we’re looking for may not lie in our version of the “sweet spot”.

    It is definitely worth considering that other options do exist besides water and carbon. Alternative biochemists speculate that there are several atoms and solvents that could potentially spawn life. It is also worth considering that because humans are carbon-based beings, who do their lab work under conditions on planet Earth, we may be a bit biased towards carbon thinking.

    Full article here: