by Paul Gilster | Feb 13, 2008 | Astrobiology and SETI |
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).
by Paul Gilster | Feb 12, 2008 | Deep Sky Astronomy & Telescopes |
By Larry Klaes
2008 marks the 45th year of operation for the Arecibo Observatory, the largest single radio telescope on Earth. Maintained and operated by Cornell University since its opening in 1963, Arecibo has definitely made its share of contributions to our knowledge of the cosmos.
To cite but a few examples, astronomers beamed powerful radar signals from the one thousand foot wide radio telescope onto the planet Mercury in 1965 to determine its rotation rate and again in 2007 to demonstrate that the world’s core is molten. Arecibo confirmed the existence of neutron stars, the remains of massive suns that had become supernovae, in 1968; in 1990 it found the first known exoplanets around a type of rapidly rotating neutron star called a pulsar. The first deliberate electromagnetic message aimed to any technological alien intelligences in the Milky Way was broadcast from Arecibo in 1974. In 1989, the observatory’s radar returned the first images of a passing planetoid, revealing its shape and dimensions to scientists.
For six months in 2007, workers gave the giant radio telescope’s platform and focal-point structure, which hangs high above the Puerto Rican jungle where Arecibo resides, its first serious paint job in four decades. This project was designed to keep Arecibo operating efficiently for many years to come, even as its near-term future is being threatened by a loss of funding from the National Science Foundation (NSF), which operates the observatory in a cooperative agreement with Cornell University.
Arecibo’s first assignment after its makeover was to examine the space object known as 3200 Phaethon, named after the son of the Greek Sun god Helios – an appropriate designation, as this relatively small celestial object comes closer to our yellow star than any other known member of the Solar System.
Image: Arecibo’s ongoing work not only teaches us about the cosmos but provides critical planetary defense by identifying Earth-crossing asteroids. Credit: NAIC/Arecibo Observatory, a facility of the NSF.
The first planetoid to be discovered by a spacecraft (the InfraRed Astronomical Satellite, IRAS, in 1983), Phaethon may actually be an extinct comet, as debris from this body is also the source of the Geminids meteor shower, which appears in Earth’s sky every mid-December.
A team of scientists working with and at Arecibo, which include Cornell University assistant professor of astronomy Jean-Luc Margot, bounced radar beams off Phaethon last December. The team wants to know more about how solar energy affects planetoids that travel near the Sun, which can have their orbits and rotation rates gradually changed over time through long exposure to sunlight. What the scientists learn from these observations will help in our understanding of the many small space bodies that continually cross Earth’s orbit, some of which may one day be on a collision course with our planet and threaten all life upon it.
Arecibo’s impressive capabilities were also in evidence at the American Astronomical Society’s (AAS) 211st meeting in Austin, Texas, last month, when astronomers announced the discovery of methanimine and hydrogen cyanide, two types of molecules which form the amino acid glycine when combined with water. Amino acids are the building blocks of proteins, which are large organic compounds that perform many important functions in the cells of every living being on Earth.
These molecules were found in a galaxy named Arp 220 located some 250 million light years from our Milky Way galaxy. The starlight emitted from Arp 220 currently being witnessed by astronomers on Earth took 250 million years traveling at the speed of light (186,000 miles per second) to reach our planet across intergalactic space. When that light left the far-off island of stars all those ages ago, dinosaurs had yet to appear on Earth.
“The fact that we can observe these substances at such a vast distance means that there are huge amounts of them in Arp 220,” said Emmanuel Momjian, one of the Arecibo astronomers who made the find. “It is indeed very intriguing to find that the ingredients of life appear in large quantities where new stars and planets are born.”
The Arecibo astronomers utilized the telescope’s main spectrometer to make the discovery of these molecules (a spectrometer is a device that measures light properties at specific frequencies of the electromagnetic spectrum). Team member Tapasi Ghosh noted that they were not searching for any particular molecule in that active galaxy, so their finding was “incredibly exciting.”
Another astronomical find involving Arecibo announced at the same AAS meeting in Texas regards a new determination about neutron stars and black holes, two types of aging massive suns that collapse and crush themselves into incredible densities. Arecibo Observatory astronomer Paulo Freire and his team studied the binary pulsar M5 B in the globular star cluster Messier 5, located in the constellation of Serpens the Snake, where the galaxy Arp 220 also resides. Using the facility’s spectrometer from 2001 to 2007 to measure the rotating beams of powerful radiation emitted from the neutron star’s poles, Freire was able to determine the mass of this dense stellar remnant accurately.
Freire discovered that this particular neutron star remained in its current state at 1.9 times the mass of our Sun. Astronomers previously thought neutron stars would collapse into black holes at less massive states.
“[This find] means that to form a black hole, more mass is needed than previously thought,” Freire told the Cornell Chronicle. “Thus, in our Universe, black holes might be more rare and neutron stars slightly more abundant.”
The above stories represent just some of the dozens of astronomical projects currently being conducted at the observatory. No doubt even more amazing things will be learned about our cosmos in coming years, thanks to that giant dish sitting on a distant island in the Caribbean Sea.
by Paul Gilster | Feb 11, 2008 | Exoplanetary Science |
We have a long way to go in the study of circumstellar disks, especially around smaller stars. Given the difficulty of making such observations, work at the Subaru Telescope has focused on stars more massive than the Sun in hopes of studying the more apparent structure of the disks around such stars. But FN Tauri is an exception. The young star is a tenth of the Sun’s mass, its disk seven times lighter than the lowest mass disk previously imaged, which was around the star TW Hydrae. The hope is to extend our knowledge of planetary formation more broadly across stellar types to learn what kind of worlds they form and where.
The team of Japanese researchers performing this work used the Coronagraphic Imager with Adaptive Optics (CIAO) at the Subaru Telescope. What they’ve learned about FN Tauri is that the thick, roughly circular disk, with a radius of 260 AU, is relatively featureless at this point in the star’s evolution (FN Tauri is thought to be a mere 100,000 years old). Thus far it seems that the more massive protostellar disks are those more likely to show asymmetries. With a mass estimated at 6 percent of the star, the FN Tauri disk becomes thicker with increasing distance, making it appear brighter than expected.
Image: FN Tauri captured by CIAO instrument mounted on the Subaru Telescope. This infrared image taken at 1.6 micron shows an almost face-on circular disk structure. The light from the central star FN Tauri itself is blocked by the coronagraph mask. Somewhat symmetrical darker areas are the blocking by the secondary mirror support. Credit: Subaru Telescope/NAOJ.
In the class of stars known as T Tauri, FN Tauri is powered by the contraction of its disk as it moves toward the main sequence and thus offers a look at early stellar formation. Based on current models, the protoplanetary disk around the star could produce no planets larger than Earth and could form smaller worlds within 30 AU. New adaptive optics at the Subaru site (located on the summit of Mauna Kea in Hawaii) should make still more detailed observations of disk structures possible, along with analysis of the material within them. That makes work like this valuable not only in itself, but also in terms of target gathering for the more powerful telescopes planned for next generation exoplanet hunting.
The paper is Kudo et al., “Discovery of a Scattering Disk around the Low?Mass T Tauri Star FN Tauri,” Astrophysical Journal 673 (January 20, 2008), L67-L70 (abstract).
by Paul Gilster | Feb 9, 2008 | Culture and Society |
‘Closed time-like curves’ are just the ticket if you want to travel in time. Theoretically, a sufficient distortion of spacetime could make a time machine possible, but Irina Aref’eva and Igor Volovich (Steklov Mathematical Institute, Moscow) take the idea out of the purely theoretical by suggesting that the Large Hadron Collider set to debut this summer at CERN may provide sufficient energy to create a tunnel through time. A tiny tunnel, to be sure, sufficient solely for subatomic particles, but a possible demonstration of wormhole concepts that on a far larger scale could one day prove productive for fast transportation to distant places and remote times.
But as to the argument that the LHC’s operations could establish Year Zero for time travelers (creating the needed first instance of a time machine to which future travelers would be able to return), I’ll take a pass. Surely if massive energies are what it takes to establish such a wormhole (itself a purely theoretical concept, and one that requires yet another theoretical idea — phantom energy — to hold it open), then the universe has supplied us with previous instances of ‘closed time-like curves’ in highly energetic events reaching back to the Big Bang. Does that mean a time traveler could only travel back 13.7 billion years? If so, that’s plenty of temporal territory to play in, but the Fermi question equivalent for time travelers is, where are they?
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Every time I run an Enceladus story, another one emerges, this time a demonstration that that on-again, off-again subterranean ocean may actually be there. Or maybe, given the size of the Saturnian moon, we should call it a subterranean ‘lake.’ Cassini team member Jürgen Schmidt (University of Potsdam) and team have been studying the process by which ice particles from the moon’s geysers form and work their way through cracks in the crust to reach the surface. Says Schmidt:
“Since Cassini discovered the water vapor geysers, we’ve all wondered where this water vapor and ice are coming from. Is it from an underground water reservoir or are there some other processes at work? Now, after looking at data from multiple instruments, we can say there probably is water beneath the surface of Enceladus.”
According to Schmidt’s study, an internal lake at a temperature of about 273 degrees Kelvin (O degrees Celsius) is the best way to make sense of what we see coming out of Enceladus’ geysers. The model invokes ice grains condensing in a vent following evaporation from a liquid body of water, consistent with the steady production of ice particles Cassini sees. The possibilities for life within Enceladus seem to shift with every passing paper, but that’s to be expected as we work out a model that multiplies conceivable biospheres in the outer Solar System. The paper is Schmidt et al., “Slow dust in Enceladus’ plume from condensation and wall collisions in tiger stripe fractures,” Nature 451 (February 7, 2008), pp. 685-688 (abstract).
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Speaking of outer planet moons, I see that NASA will be running tests on a robotic probe called the Environmentally Non-Disturbing Under-ice Robotic Antarctic Explorer (ENDURANCE) in a few days at Lake Mendota (on the campus of the University of Wisconsin). The long-range goal is to establish whether the autonomous vehicle’s systems might be suitable for operating under the ice of Europa, mapping the local environment and taking samples of microbial life. The plan is to ship the probe to Antarctica for further tests later in the year. All of which takes on growing significance as we work out the huge theoretical question of whether life may not take hold in environments once thought barren, with implications that are obvious for what is going on around other stars.
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Orbiting Frog has the 40th Carnival of Space, and while I usually try to point to stories of particular interest for interstellar purposes, the highlight of this week’s carnival may well be the collection of space wallpapers on the Orbiting Frog site itself. Most are simply gorgeous, reminding me that in addition to the beauties of theory, a deeper response to the glories of the cosmos must also include simple awe.
by Paul Gilster | Feb 8, 2008 | Exoplanetary Science |
When you have assets in space, the thing to do is redeploy them as needed. That creates what’s called an ‘extended mission,’ and the latest spacecraft to get one is Deep Impact, the vehicle whose impactor made such a splash when it was driven into comet Tempel 1 in the summer of 2005. That July 4 explosion was memorable enough, but under the name EPOXI the doughty craft leaves its vaporized impactor behind and moves on to two other missions, one of which has direct extrasolar applications.
For one of EPOXI’s twin goals is to observe five nearby stars known to have transiting exoplanets. Observations began on January 22. The ‘hot Jupiters’ around the five stars have been confirmed previously, but EPOXI’s mission is to see whether any of these transiting gas giants is accompanied by other worlds in the same stellar system. Perhaps the most intriguing aspect of the investigation is summed up by Drake Deming (NASA GSFC): “We’re on the hunt for planets down to the size of Earth, orbiting some of our closest neighboring stars” (italics mine).
Such worlds might be making transits of their own, but transit timing of the known gas giants will tell the tale, the gravity of the unseen world perturbing the transit of the larger. Deep Impact may not have been designed for this work, but the prospects are exciting. What stands out about recent exoplanet findings from space is the success of COROT, once thought to be a relatively modest mission compared to efforts like Kepler and the much more ambitious Darwin, yet a spacecraft that is producing results far beyond what many of us had expected. Can Deep Impact, under its new name, make a successful transition and surprise us again?
Nor is exoplanet hunting the only goal of the extended mission. EPOXI is actually a conflation of two missons: Extrasolar Planet Observation and Characterization, as just discussed, and the Deep Impact Extended Investigation, aimed at taking a close look at comet Hartley 2 with a flyby on October 11, 2010. So the cometary challenge remains, but wouldn’t it be extraordinary if we turn what had been Deep Impact into the platform that flags the first Earth-sized exoplanet? We’ll also learn much about those hot Jupiters, including information about their atmospheres and the possibility that one or more may have moons or rings.
Keep your own eyes on EPOXI’s blurry vision. As discussed in these pages back in July, the Deep Impact telescope is out of focus, which actually makes for better photometry, allowing the system’s CCD to collect more photons before it becomes saturated. Drake Deming explained this puzzling point to Emily Lakdawalla last summer: “With a defocused image, we have about 75 pixels collecting light for us, so we can collect lots of photons in each exposure without saturating, and that gives us the high signal-to-noise ratio that we need.”
A blurry view, then, may be just the ticket as we go hunting for planets of Earth size and above. A final EPOXI aim: To observe the Earth in visible and infrared wavelengths. Looking back at our own terrestrial world provides useful data points when we begin to collect information about such worlds around other stars. All this from a mission that’s clearly a long way from exhausting its useful life, making the case that if you build the hardware right, the mission possibilities continue to grow.
