Living in the Universe

Life at the Red Edge

Last Week of February 2008

My topic this week is a story based on a press release from up the I-10 freeway at Arizona State University. They’re our deadly rivals in sports, but in science we all get along. Researchers from ASU and Washington University are reporting in an online edition of the Proceedings of the National Academy of Sciences that they have sequenced the genome of a cyanobacterium called Acaryochloris marina. Through its production of chlorophyll d, this microbe can absorb “red edge” or near-infrared long-wavelength light, light with such a long wavelength that it’s invisible to the naked eye.

Acaryochloris marina has a massive genome of over 8.3 million base pairs, and it’s among the largest of fifty-five known strains of cyanobacteria in the world. It’s the first organism containing chlorophyll d to be sequenced, and the data will help scientists understand how it and its unique genes have evolved over time. For a recap on photosynthesis: in this process, plants convert energy from the Sun into chemical energy in the form of glucose or sugar. The chlorophyll in plants, mostly of the a and b varieties, absorbs more blue and red light from sunlight and less green light. It reflects the green light, and so plants appear green. That’s normal chlorophyll. Chlorophyll d harvests light from a region of the spectrum that few other organisms can, and this enables the organism to carve out its own special evolutionary niche.

There are major implications of this work for agriculture. One could imagine the transfer of this biochemical mechanism to other plants where they can then use a wider range of the light spectrum and thus become plant powerhouses, deriving increased energy by employing a new photosynthetic pigment. There’s also a bioenergy link. Chlorophyll d could be used for crops that are turned into fuels or to generate biomass. It may also have interesting implications for space science, helping develop productive crops for use in space stations or settlements where energy efficiency is very important.

The leader of the study is Robert Blankenship from Washington University. He says that with every gene of Acaryochloris marina now sequenced and annotated the immediate goal is to find the enzyme that causes a chemical change that makes chlorophyll d different not only from the more common a and b forms but also from the nine other forms of chlorophyll. “The synthesis of chlorophyll by an organism is complex, involving seventeen different steps,” said Blankenship. “Somewhere near the end of this process, an enzyme transforms a vinyl group to a formyl group to make chlorophyll d. This transformation of chemical forms is not known in any other chlorophyll molecules.”

The researchers said that harvesting solar power through plants or other organisms that could be genetically altered with the chlorophyll d gene could make them solar power factories that could generate and store solar energy. Imagine a seven-foot tall corn plant genetically engineered with the chlorophyll d gene to be expressed at the base of the stock. While the rest of the plant is synthesizing chlorophyll a, and absorbing short wavelength light, the base is absorbing red edge light at seven hundred nanometers. Energy could be stored at the base without competing with any other part of the plant for photosynthesis. The altered corn using that synthetic chlorophyll d gene would be a super plant because of its extra ability to harness energy from the Sun.

This model actually may be similar to how Acaryochloris marina operates in the South Pacific, specifically Australia’s Great Barrier Reef. Discovered just eleven years ago, the cyanobacterium lives in a symbiotic relationship with a sponge-like marine animal popularly called a sea squirt. Acaryochloris marina lives underneath the sea squirt, which is a marine animal that lives attached to rocks just below the surface of the water. The cyanobacterium absorbs red edge light through the tissues of the nearly transparent sea squirt. “The genome,” says Blankenship, “is fat and happy. Acaryochloris marina lies down there using far red light that no one else can use. The organism has never been under strong selection pressure to maintain a modest genome size. It’s in a sweet spot. Living in this environment allowed it to have such a dynamic genome expansion.”

The general conclusion for this work for astrobiology is important. If energy from the invisible infrared can be harnessed by normal biological mechanisms familiar on Earth, that means life doesn’t need a Sun-like star, one that puts out most of its energy as visible light. Biology could be happy on a planet around a very dim red star, and most stars in the universe are just like that. The real estate that we should consider habitable just got a whole lot larger.

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There’s No Place Like Home, Yet

Fourth Week of February 2008

There’s no place like home, yet, but astronomers are getting that much closer. Somewhere over the rainbow astronomers anticipate finding analogs of the solar system and clones of the planet Earth. Since 1995, over two hundred and fifty planets have been found beyond the solar system—exoplanets as they’re called—but very few of them are in systems that even faintly resemble our own. In many cases giant Jupiter-like planets whirl around in orbits that are closer to their star than Mercury is to the Sun. But are these really typical of what’s out there in the universe? Also, almost all of these planets were discovered by a Doppler wobble method in which astronomers measure the gravitational tug of planets on their parent star as they whirl around it. This technique is particularly sensitive to massive planets close to their stars.

So there was great excitement last week when astronomers said they had found a miniature version of our own solar system five thousand light years away across the galaxy. It’s the first planetary system that really looks like our own, with outer giant planets and room for small inner planets, although no terrestrial planets have been found yet. Scott Gaudi, assistant professor at Ohio State, led the international team of 69 professional and amateur astronomers who announced the discovery in a big news conference. He said, “It looks like a scale model of our solar system.” Their results are being published in the journal Science.

They say it means that our solar system may be more typical of planetary systems across the universe than have been thought. In this new system a planet about two-thirds the mass of Jupiter and another about ninety percent of the mass of Saturn are orbiting a reddish star about half the distances that Jupiter and Saturn circle our own Sun. The star itself is about half the mass of the Sun, a little cooler and a little redder. Neither of these two giant planets is a likely abode for life as we know it, but Dr. Gaudi and the team say that warm, rocky planets suitable for life could easily exist undetected in the inner parts of the system.

One of the exciting things about this discovery is the way it was made. It used a different technique than the Doppler technique, one that favors planets more distant from the star. It’s based on a trick of gravity called microlensing. If as stars and planets move to-and-fro in space two of them should become almost perfectly aligned with the Earth, the gravity of the nearby star can bend and magnify the light from the more distant one, causing it to get brighter for a few weeks or months. If the alignment is perfect, any big planets attending the nearby star will also be part of this process, adding their own little boost to the distant starlight. You never actually see the distant planet or the distant star. This is an indirect technique for finding planets and it’s a one-off; the signal never repeats.

That’s exactly what happened on March 28 a year or so ago (with the research paper just being published last week), when a star 5000 light years away in the constellation Scorpius began to pass in front of one twenty-one thousand light years more distant, causing it to brighten and then fade. The event was picked up by OGLE, the Optical Gravitational Lensing Experiment, which is a worldwide collaboration of observers who watch out for such rare events. OGLE immediately issued a worldwide call for anyone who could point a telescope at what is one of their best candidate stars around which to find a planet.

For the next two weeks the pace was frenetic. Among those who provided crucial data, and who appear as lead authors on the paper in Science, are a pair of amateur astronomers from New Zealand, Jennie McCormick and Grant Christie, both of whom are members of another group called the Microlensing Follow-Up Network, or MicroFUN. Jennie McCormick had already been involved in the discovery of a planet several years ago by the microlensing technique. She’s both an amateur astronomer and a full-time mom, and she was quoted as saying, “It just goes to show you can be a mom, you can work full-time, and you can still go out there and find planets.” Exactly.

To the experimenter’s surprise, by clever manipulation of their data, they were able to dig out not just the masses of the star and its 2 planets but rough approximations of their orbits, which confirmed its similarity to our solar system. Microlensing is poised to become a new, powerful tool in the planet hunter’s arsenal. These two planets are only the fifth and sixth to be discovered by microlensing so far, and the Scorpius event is the first where the alignment of the stars was close enough for astronomers to detect more than one planet at once. But this success indicates that microlensing is a technique for the future, and it may just become the way we find places like home.

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Life in the Lost City

Third Week of February 2008

The topic today is Life in the Lost City. I’m not referring to Atlantis but to another subterranean world. In the 1970s, deep under the ocean, just when we thought we knew everywhere life was on Earth, entire ecosystems were found living in total darkness where magma superheated water and emerged into frigid water at the bottom of the ocean. There were microbes, blind krill and translucent fish, and all sorts of living organisms this far from the Sun’s energy.

Two papers recently have brought to light a place called the Lost City, a contender for one of the places where life may have started four billion years ago deep under the ocean. Hydrocarbons, the molecules critical for life, are being generated in this region by the interaction of seawater with the rocks at the Lost City hydrothermal vent. This place is located in the middle of the Atlantic Ocean.

The lead authors on the paper, Giora Proskurowski and Deborah Kelley, say that they’ve ruled out carbon from the biosphere as a component of the hydrocarbons in Lost City vent fluids. Hydrocarbons, molecules with different combinations of hydrogen and carbon, are key to cellular life. For example, cell walls can be built from simple hydrocarbon chains, and amino acids are short hydrocarbon chains hooked up with nitrogen, oxygen, or sulfur. According to Proskurowski, “The generation of hydrocarbons was the very first step. Otherwise, Earth would have remained lifeless.”

There are two hypotheses for how life on Earth started. Some researchers still believe that the building blocks of life made their way from outer space. Others hypothesize that the right ingredients were generated by geological processes on Earth, perhaps at hydrothermal vent systems where seawater seeps into the seabed, picks up heat and minerals, until the water is so hot it vents back into the ocean. The hydrothermal vents in the Lost City were discovered by Deborah Kelley and her colleagues during an expedition in 2000 and they are very different from the black smoker vents that scientists have known about since the 70s. Black smokers are called this because it looks like smoke is billowing from them. The smoke is in fact dark iron and sulfur rich minerals precipitating when the super hot vent waters, they can be as hot as 800° F, meet the icy cold depths. The spires and mounds that form from the superheated water are modeled mixtures of sulfide minerals.

By contrast, the Lost City structures are nearly pure carbonate, the same material as limestone in caves, and they range in color from white to cream to grey. The structures and the cliffs in the Lost City range from the size of little mushrooms to an eighteen-story column called Poseidon that dwarfs most of the black smoker vents by hundreds of feet. The field was named Lost City in part because it’s on top of a submerged mountain named Atlantis, and it was discovered by chance during an expedition on board the research vessel Atlantis. The water venting at Lost City is 200° F. The fluids don’t get as hot as the black smokers because the water isn’t heated by magma but rather by heat released by chemical processes.

Natural occurring carbon dioxide is locked in mantle rocks, and at Lost City the reaction between rock and seawater produces ten to a hundred times more hydrogen and the hydrocarbon methane than a typical black smoker system. That’s why it makes excellent raw materials for life. Analysis of the rocks from Lost City shows that the hydrocarbons are not coming from the living biosphere. Rock in contact with seawater has a very consistent ratio of carbon dioxide to helium, but the rock at Lost City had a strikingly different ratio. It turns out that the depleted amount of carbon dioxide in the rocks roughly equals the amount of hydrocarbons being produced in the fluids. “Lost City is exceptional,” as Deborah Kelley says, “Because chemical reactions in the sea floor produce acetate, formate, hydrogen, and alkaline fluids. All of these substances may have been key to the emergence of life on Earth.”

In addition, acetate and formate found in the Lost City fluids may have been an important energy source for the ancestors of methanogens, the microorganisms that live off the methane at places like Lost City. It’s one more bit of evidence about where life may have originated. Where is this bizarre place? It’s about 2300 miles east of Florida on the Mid-Atlantic Ridge at a depth of 2600 feet. Microorganisms there thrive in alkaline vent fluids, some of which are nearly as caustic as liquid drain cleaner. The Lost City microbes live off methane and hydrogen instead of the carbon dioxide that’s a key energy source for life at the black smoker vents. In the early Earth there were probably plenty of places where mantle rock may have met the bottom seawater and produced complex and interesting chemical reactions, so Kelley is sure that there are other Lost Cities waiting to be found.

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Follow the Energy

Second Week of February 2008

If you want to find life elsewhere in the universe, follow the water according to NASA and many astrobiologists. The Earth is a water world, and in addition to the Earth it’s likely that Mars may liquid water kept under pressure on its surface, and also perhaps half a dozen moons in the outer solar system. As far from the Sun as they are, moons of gas giant planets may have liquid water under a crusty surface.

Water is one of the most abundant molecules in the universe so it’s sensible to follow the water as a strategy for looking for life, but as we were reminded late last year in a report for the National Academies of Science, we should also to loosen the envelope of what we consider life. That report, titled The Limits of Organic Life in Planetary Systems, said that there are so many ways that life might evolve and so many chemical and biochemical bases for life that we should be generous in considering what is a minimum requirement. Following on from that, a paper in Astrobiology Magazine recently says we should follow the energy in looking for life. The opening paragraph of the paper which summarizes the rationale and the approach:

“A key challenge in astrobiology is to comprehend life and its interaction with the environment at a level sufficiently fundamental to embrace alternative biochemistries that may be encountered in a search for life elsewhere. Life on Earth presents us with a single, albeit highly diversified, biochemical model around which to build this comprehension. This model is extremely valuable in providing an empirical starting point for understanding metabolic potential and environmental tolerance and as a continuing reality check on whatever generalized concepts of life may be developed. Reference to this single example, however, also carries the risk of narrowing our sense of possibility of leading us to define biochemistry, habitability, and biosignatures in terms so specific that they may exclude different forms of life.”

Sixty years ago Nobel Prize winner Erwin Schrödinger brought life’s definition down to its fundamental elements. Life consumes and transforms energy, and so energy is perhaps more fundamental to the definition of life than water, which is simply an ingredient. Water is a very useful solvent and clearly essential to life on Earth but maybe not elsewhere.

The study of terrestrial life in terms of its energy usage reveals several common principles. First, the core metabolic processes function across all organisms from human beings to the tiniest microbes. Second, energy usage encompasses two fundamental ideas: power, or how energy is used over time, and something that’s called voltage, which is the amount of energy in a metabolic event. There seem to be minimum values of power and voltage in the way that life uses energy; below these values life is simply not possible on Earth. Finally, there is a direct and obvious link from environment to biology by a small number of biochemical schemes in molecules, and every form of life on Earth uses one of these small number of biochemical schemes.

So while water is important in general, and essential on Earth and maybe other locations, there is energy everywhere including places where there’s no water. If we think of energy as fundamental, life could get it in many ways. It could get it from gravity. It could get it from starlight or geothermal energy deep within a planet. Most importantly, life on Earth and probably elsewhere gains energy by rearranging molecules. There is abundant free chemical energy simply waiting to be tapped in many environments. Some terrestrial microbes get their energy from metals that we would consider toxic, for example, and since molecules will exist elsewhere in the universe in different concentrations and in very different physical forms than the Earth, there’s an abundance of ways life could gain its energy. The most general way to look for life is to follow the energy in the universe, and that may be the bottom line for astrobiology.

To close, here’s a tag on a story from a few weeks ago about the best message to send ET. Perhaps sending the classics is the best idea. No I don’t mean classical music; I mean the Beatles. On Monday, NASA broadcast the Beatles song Across the Universe a little ways across the galaxy to Polaris, the North Star. The first ever beaming of a radio song by the space agency directly into deep space is driven by nostalgia for the most part, not science. It celebrates the fortieth anniversary of the song, the forty-fifth anniversary of NASA’s deep space network, and the fiftieth anniversary of NASA. Paul McCartney told NASA through a Beatles historian, “Send my love to the aliens. All the best, Paul.” The song, written by McCartney and Lennon, may have a ticket to ride and will be flying at the speed of light, but it will still take 431 years to reach its destination because Polaris is 2.5 quadrillion miles away.

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The Non-Story Behind UFOs

First Week of February 2008

UFOs: alien visitors or mundane terrestrial phenomena? You be the judge. This week’s morality play takes place in three acts. Act One was back on January 8 in the small farming community of Stephenville, Texas, where nightfall usually only brings clear skies and starry nights. Three weeks ago, residents were abuzz over reported sightings of UFOs. Several dozen people, including a pilot, a county constable, and several business owners say they saw a large, silent object with bright lights flying low and fast. Some people reported seeing fighter jets chasing it. Listen to Steve Allen, a freight company owner and pilot. He said, “People wonder what in the world it is because this is the Bible Belt and everyone is afraid it’s the end of times.” He said the object that he saw was a mile long and half a mile wide. “It was positively, absolutely nothing from these parts.”

While federal officials said at the time there was a logical explanation, locals swore that it was larger, quieter, faster, and lower to the ground than an airplane. They also said the object’s lights changed configuration, unlike those of a plane. People in several other towns offered similar descriptions. Machinist Ricky Sorrells’ friends made fun of him when he told them he saw a flat metallic object hovering three hundred feet over a pasture behind his Dublin, Texas, home, but he heard of several accounts so he came forward. Sorrells said he had seen the object seven times. He watched it through his rifle’s telescopic lens and described it as very large and without seams, nuts, or bolts.

At the time, Major Karl Lewis, spokesman for the 301st Fighter Wing at the Joint Reserve Base Naval Air Station in Fort Worth, said no F-16s or other aircraft from his base were in the area on the night of January 8 when most people reported the sightings. “I’m ninety percent sure this was an airliner,” said Lewis. “With the sun’s angle, it can play tricks on you.” Officials at the region’s two Air Force bases also said that none of their aircraft were in the area. The Air Force no longer actively investigates UFOs but there are about 200 UFO sightings reported each month, mostly in California, Colorado, and Texas according to the Mutual UFO Network. Fourteen percent of Americans, or roughly one in five, saw a UFO at some time in the past according to the Associated Press.

That was the story a few weeks ago, and people dove right into it. Two weeks later on the web “UFO photos” was the third fastest moving search item on all web sites according to Hitwise, an online measurement company. Among news and media sites, “UFO sightings” was number four of all searches in the US, and “Texas UFO” was number five. Obviously search term behavior is a good indicator of what’s on people’s minds. So this was one of the hottest stories a few weeks ago.

Now for Act Two. Just last week the bubble burst, or did it? Ten Air Force reserve F-16 fighter jets were the cause of the lights seen over parts of central Texas earlier this month, according to CNN. Many had believed them to be UFOs according to an Air Force reserve news release. “The F-16s were on a nighttime training mission over the Brownwood Military Operating Area near Stephenville, Texas,” the statement said. A military operating area is airspace designated for military training. People had seen lights moving fast across the night sky, and the Air Force originally reported it had no aircraft flying that night. But on Wednesday last week an Air Force Reserve statement said that it made a mistake in its initial reporting and that there were planes in the area that night.

Here’s what the release actually said. “In the interest of public awareness, Air Force Reserve Command Public Affairs realized an error was made regarding the reported training activity of military aircraft.” Spokesman Karl Lewis said that the error in the reporting resulted from an internal communications problem between offices at the base. He said he received the flight information earlier this week, confirmed it with officials at the base, and sent a news release out on Wednesday. The release said, “The planes were in the area from 6 pm to 8 pm, just the time when many people had reported seeing the lights.” Lewis said the planes were from the 457th Fighter Squadron based at the Reserve Naval Base outside of Fort Worth, Texas.

So you’d think that was the end of the story, wouldn’t you? Well, I did a little Google News search, and found an interesting thing. There were ten times more news releases across the Internet on the original story than there were on the story last week that corrected the fact that these were not UFOs but fighter jets. That’s a big part of why the idea of UFOs persists. The reports are made, people speculate, they draw conclusions, and when new evidence comes in later, people’s attention has moved on and so the error is never corrected. That was Act Two.

What about Act Three? You’d think it would all be over at this point? Well not according to Kenneth Cherry, the Texas Director of the Mutual UFO Network which took more than fifty of the reports from locals at the original January 8 sighting. The announcement from the Air Force that fighter jets were training that night also did little to satisfy Texas town residents who swear that what they saw on January 8 was no airplane. Some even said it bolstered their claims because several people reported seeing at least two fighter jets chasing a strange object. According to Cherry, “This supports our story that there was UFO activity in that area. I find it curious that it took them two weeks to fess up. I think they’re feeling heat from the publicity.” So there you have it. It’s a cover up. And even when the evidence comes in, people like Mr. Cherry can always believe what they wanted to believe. And so UFOs live on. And on and on and on.

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