Living in the Universe

An Astrobiology Cornucopia

Fourth Week of April 2008

Ladies and Gentleman, boys and girls, earthlings and aliens, I just came back from AbSciCon, the astrobiology science conference in Santa Clara, and my head is so full of astrobiology that I think it might explode. Three days, six hundred and fifty papers, two thousand authors total, twenty-eight countries represented. I gave an education talk on my Second Life work, but the breadth of research results made it an incredible meeting. I can barely give you a sense of what was involved, but I’ll select three papers to talk about in particular.

The keynote address at the beginning of the first day was a wonderful overview of the cosmic context of life given by Lord Martin Rees. Yes, if you weren’t aware of it, over in Britain there’s a scientist who’s so famous he not only was knighted and became Sir Martin Rees but he is now in the House of Lords. Even Isaac Newton didn’t go beyond a knighthood. Martin Rees is also the Astronomer Royal, and he made a joke about the fact that his primary duty there involves casting the queen’s horoscope. He’s the president of the Royal Society, and he holds Newton’s Chair of Astronomy hundreds of years later. He also happens to be a really nice guy.

Rees a brilliant and preeminent cosmologist, and he talked about the setting for life in the universe on the largest scales. He reminded the audience that we expect the universe to be fecund and have material that can form life and biology because of the way carbon has been created and flung out from stars through cosmic time. He also—unusually for most scientists—was strongly supportive of SETI, pointing out that it’s an important philosophical experiment to actively look for extraterrestrial intelligence, though he noted that we’re only likely to detect a small fraction of all the possible brains out there. He made several references to science fiction and in one aside said that he preferred first-rate science fiction to second-rate science any day, but mostly he was talking about cosmology.

He homed in on the six numbers that describe the universe on the largest scales and the fact that some of those numbers are poised at values that permit the existence of life. These cosmic coincidences have begged an explanation by cosmologists, and the most popular one involves the fact that we live in a multiverse, a “small” pocket of space-time that could be part of a much larger construct. Most of these universes in the multiverse are sterile because their physical properties would not permit stable atoms or long-lived stars or biology of any kind, but ours of course is not. He also gave a sense of how vast the totality of the universe could be, so vast that it’s kaleidoscopic in proportion and so vast that all the possible probability outcomes may occur somewhere in space and time. It was a head spinning talk, and it really set the scene for all the work that would follow.

The second talk I want to highlight was given by Richard Muller at the University of California, Berkeley. He gave a wonderful overview of a new signal seen in the extinction of marine creatures on Earth in the past half billion years, that shows a strong periodicity. We know there have been mass extinctions in the history of life on Earth, but it’s mostly been thought that they were random, probably caused by cosmic impacts from space or some sort of climate catastrophe. But Muller has used an enormous compendium by the late Jack Sepkoski of fossil marine data to do a new analysis, and he’s found a very strong evidence for a sixty-two million year cycle in the death of species.

His new analysis involves a lot of new data that he was willing to share with anyone in the audience, making available his Excel spreadsheet. It involves tens of thousands of marine species. The sixty-two million year cycle only leaps out when a new age calibration is used. It turns out that the ages for fossil dating over the past half billion years had errors of up to ten or twenty million years, and that was enough to smear out this signal. But with the new age calibration it was obvious in all his graphs. It’s seen separately in trilobites, bivalves, porifera, and brachiopods, less strongly in gastropods, cephlopods, and fish. He also sees weaker evidence for a hundred and forty million year cycle. The existence of two periodicities in the extinction of marine creatures over half a billion years begs for an astronomical explanation because something that’s periodic is probably coupled to orbits or gravity in some way.

The potential explanation of these two cycles was provided by a pair of talks that followed by Mikhail Medvedev and Adrian Melott. The hundred and forty million year cycle, for which the evidence is still fairly weak, is probably caused by the periodic passage of the Sun and the Solar System through the spiral arms of the Milky Way galaxy. The sixty-two million year cycle exactly matches the period of the Sun’s motion up and down in the plane of the Milky Way galaxy.

Imagine the Milky Way and its disk as an old style phonograph record, a 33 record, warped by heat so it is corrugated and the Sun travels up and down and in and out of the plane of the galaxy as it goes round, with a two hundred and fifty million year orbit and a sixty-two million year cycle for the up and down motion. At its maximum excursion from the plane of the Milky Way, the Earth and the Solar System sees an increased flux of cosmic rays, and this increased flux of cosmic rays causes mutation of DNA, climate change, and the combination is a one-two punch that kills species. So we have a very neat explanation for the periodicity of extinctions. It’s caused by our large-scale astrophysical environment, and we might wonder if other life bearing planets in the Milky Way galaxy are subject to similar periodicities.

The last talk I want to mention was by Denise Herzing from the Wild Dolphin Project in Florida. The Wild Dolphin Project is just what you might imagine. This woman has an incredible job. For nearly twenty-five years she’s spent five months of the year out in the Bahamas tracking, playing, and working with Atlantic spotted dolphins. She’s a behaviorist, and they try to be as least intrusive as possible in the dolphin culture. For that span of time they’ve studied two hundred individuals over three generations, and they know many of these individuals by sight and behavior after that length of time.

Remember, these are wild dolphins. This is not a controlled situation, and yet they’ve managed to record sounds to correlate behavior and vocalization and learned an enormous amount about dolphins that wasn’t known before. As Carl Sagan noted some years ago, we’ve managed to train dolphins to speak about two hundred words of English by tapping out symbols on a keyboard but we still speak exactly zero words of dolphin. So who’s smarter? Denise’s presentation made it clear that these incredible creatures display fantastically complex behavior and socializations.

She and her colleagues were able to train the dolphins to use a portable underwater keyboard to tap out symbols and essentially communicate with the humans. The dolphins that participated were mostly the young females. It seems that the young males were off fighting, as in other species, and what she summarized was a rich tapestry of subtle behavior, plus evidence of substantial intelligence and problem-solving abilities and of distinct personalities amongst the dolphins. That’s perhaps a good way to leave the idea of astrobiology from this major recent gathering of astrobiologists—while we look for intelligent, interesting creatures out in space, we should remember that we share a planet with extraordinary creatures that we don’t yet fully understand.

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Your Next Vacation?

 Third Week of April 2008

The way Will Whitehorn tells it, the story began in 2003 in Mojave California on a visit to Scaled Composites, a company with a reputation for designing futuristic aircraft. Whitehorn is one of the top executives in Richard Branson’s Virgin Group, and Virgin Atlantic, Sir Richard’s airline, was sponsoring Global Flyer, a Scaled Composites creation, on a non-stop voyage around the world. On his way out of the factory, Whitehorn saw something unusual and asked what it was. Burt Rutan, head of Scaled Composites, told him it was a spaceship. He was building it for another customer, but he couldn’t say any more.

Rutan’s customer turned out to be Paul Allen, one of the Microsoft founders.  When Spaceship One, as the aircraft was called, reached space for the second time on October 4, 2004, it won the ten million dollar Ansari X Prize. The craft was taken to high altitude by White Knight, a more-or-less conventional aircraft, and then dropped whereupon its engines ignited to shoot it a hundred kilometers above the planet and thus officially into space. It reentered the atmosphere and glided onto a conventional runway.

This was an epochal moment in the history of space because it was the first time space travel began to move from the realm of governments to the realm of private enterprise. But Mr. Allen is a billionaire only interested in proving that spaceship technology would work, not in exploiting it commercially himself, and this left Rutan a problem: he had a very cool spaceship on his hands but no way of making money from it. That’s where Sir Richard Branson came in. Virgin Galactic, the company in the Virgin stable headed by Mr. Whitehorn, decided to license the technology for Spaceship One and White Knight. Virgin Galactic wants to offer sub-orbital flights to paying passengers by the end of the decade.

Virgin Galactic has accumulated a number of commercial rivals in the space tourism market so free enterprise is working. One of them is led by billionaire Jeff Bezos, the founder of Amazon, who is building a competing sub-orbital spaceship at a ranch in Texas. His space company Blue Origin is so secretive that it won’t even answer questions about its logo. But Virgin Galactic has passed an important milestone. At an event held at the American Museum of Natural History in New York in January, the company unveiled the design of its new generation of space vehicles and said the first examples have almost been finished out at Mr. Rutan’s factory. White Knight II, as it’s called, is due to roll out of the hanger soon. Test flights of Spaceship Two will start towards the end of 2009.

How does this space technology work? The combination of a carrier aircraft and a spaceship to get into space is sort of like building a two-stage rocket. Air launch rockets have a long history. Spaceship One and White Knight are essentially vastly improved and cheaper versions of the X-15 rocket plane that set speed and altitude records in the 1960s, and the B-52 Bomber that carried the Rocket Plane under its wings. However, pure rockets such as the ones that lifted the Space Shuttle won out because the space race between America and Russia emphasized speed over cost. Rockets were a cheap and proven technology, having already been developed as intercontinental ballistic missiles.

Rockets were a dead-end for the space program because they consume a huge amount of power as they claw their way up through the Earth’s thick atmosphere, and they spend most of that power lifting the fuel itself. By contrast, a rocket lifted by an airplane with wings before being launched can be made much smaller and lighter. The plane itself is light because engines breathe air. It thus needs to carry less fuel than a rocket and no chemical oxidant to burn that fuel as a rocket would. That also makes it safer, since chemical rockets are essentially giant firecrackers.  Each craft, the plane and the rocket, can therefore be optimized to do its own job. It’s also easier than designing a single vehicle with a lot of compromises to be able to do both jobs.

Virgin Galactic’s second generation of craft are based on Spaceship One and White Knight, but there are plenty of differences. White Knight II has been redesigned wholesale to lift a much larger spaceship with eight people on board instead of three. It has a wingspan similar to a Boeing 757. It’s three times larger than its predecessor and is the largest aircraft ever made from purely composite materials like carbon fiber. It has engines by Pratt & Whitney—tested and mature technologies, and with its twin boom and long wing it looks more like Global Flyer than its predecessor.

The new spaceship has been engineered to give the thrill of passengers having zero gravity swoops on the way down after they’ve watched the spaceship be released for its trip into space. There will be two pilots up front and six passengers who will have enough room to bounce around in the zero gravity. The spaceship is fueled by a hybrid rocket; called that because it contains both liquid and solid propellants. These rockets are cheaper to develop and operate, and the fuel is safer to store than purely liquid fuel ones. Spaceship One used as materials rubber and laughing gas, or nitrous oxide. Scaled Composites is studying alternatives to rubber that may improve performance. All of this pioneering technology leaves NASA and its European equivalent, ESA, in the dust.

Work is now beginning on another factory to start turning out these spacecraft in significant numbers. Virgin Galactic has ordered five spacecraft and two carrier aircraft. The spaceships will take longer to refuel for their next flight than the carrier aircraft do so thinking just as an airline would the firm has concluded it needs more spaceships than carriers. Each spaceship would eventually be capable of making two trips into space every day and the launch aircraft three or four flights. Rutan says they could operate from a number of airports and spaceports around the world. Virgin Galactic believes the fleet it has ordered should be large enough to furnish its space tourism business in the early years. Trips are expected to cost some two hundred thousand dollars each to start with, and hundreds of people have put down a total of thirty million dollars in deposits. Space travel is becoming real. As the price comes down, could this be your next vacation?

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Living in the Outer Solar System

 Second Week of April 2008

What would it be like to live in the outer solar system? It turns out to be not too bad and so life out there might not be as unlikely as we once thought. Past the orbits of Jupiter and Saturn, the Sun is a feeble dot in the sky. Temperatures are extremely cold, and yet under the surface of Titan, Saturn’s large moon, a vast ocean of water and ammonia may be lurking.

Astronomers have not directly observed this ocean, but recent observations with NASA’s Cassini spacecraft of Titan’s rotation and shifts in the location of surface features suggest a liquid ocean perhaps sixty miles under the surface. Titan is Saturn’s largest moon and the second biggest in the solar system, only slightly smaller than Jupiter’s moon Ganymede. It’s larger than Mercury and the recently demoted dwarf planet Pluto. Cassini has been looking at Saturn and its moons for several years and it has collected measurements using radar that penetrate Titan’s thick atmosphere, doing nineteen passes over the moon between 2005 and 2007.

Data from these early observations allowed researchers to locate fifty landmarks, including lakes, canyons and mountains on Titan’s surface. They looked at later radar data and found that prominent surface features had shifted by up to nineteen miles. That’s a lot. The spin of Titan’s crust is linked to winds that blow through its atmosphere, but this large a displacement of surface features would be hard to explain unless the crust were separated from its core by an internal ocean allowing the crust to essentially float. According to Ralph Lorenz of the Johns Hopkins University, who led the study, “It’s because Titan’s crust seemed so mobile that we infer this internal ocean.” He says the ocean is probably water, with a few percent ammonia, while the atmosphere is made up of nitrogen with other hydrocarbons that give Titan its orange color. Titan’s atmosphere consists of compounds that may have existed in the Earth’s primordial atmosphere, but Titan has more of the chemicals ethane and methane.

Titan is perhaps the most Earth-like landscape in the solar system and it probably has the most Earth-like weather. It’s much colder than the Earth, but the same processes that go on in our weather, particularly the formation of clouds and rain, happen on Titan, but in this case with liquid methane and not with water. Titan is thought to have hundreds of times more liquid hydrocarbons than all the known oil and gas reserves on the Earth. On Titan, these hydrocarbons rain from the sky and collect in vast deposits that form lakes and dunes.

Now the evidence of an underground ocean raises anew the possibility that life might exist deep under Titan’s surface. Similar underground oceans have been found on Europa, Calisto, Ganymede, and tiny Enceladus. Saturn’s tiny moon Enceladus is the subject of a second recent story. It has all the ingredients needed for life erupting in geysers beneath its surface and spewing into the atmosphere.  Instruments on the Cassini mission a few weeks ago revealed a concentration of water vapor, carbon dioxide, carbon monoxide, and organic material twenty times denser than expected, and the temperatures were higher than previously measured. Dennis Matson, the project scientist for Cassini, said, “Enceladus has got warmth, water, and organic chemicals, some of the essential building blocks needed for life.  We have quite a recipe for life on our hands.”

Saturn’s moons have long been of interest to scientists, particularly Titan with its enormous and significant atmosphere, but Enceladus’ chemical components are surprising because previously they’d only been found in comets. Cassini also measured surprisingly warm temperatures near the north pole. It doesn’t seem warm to us, but minus ninety-three degrees Celsius or minus a hundred and thirty-five Fahrenheit is tens of degrees warmer than scientists had expected. But it’s the liquid water that’s surprising, and those high temperatures near the surface make it likely that there’s liquid water not far below the surface.

There you have it. In the frigid depths of the outer Solar System, ranging from a large moon Titan to a tiny moon Enceladus, we have liquid water. We also have organic material, and we have energy: all the ingredients necessary for microbial life. Now, we just need a few billion dollars in NASA’s budget to send spacecraft out there with instruments that can make the careful measurements needed to be sure, and that’s at least a decade or more away. Astrobiology is not a subject for those in need of instant gratification.

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RNA World

 First Week of April 2008

This story for the first week of April 2008 is not a prank. Recent lab results have shed light on an era in the Earth’s history that’s been shrouded in darkness: the time, perhaps four billion years ago, when the motor of life first turned over. There’s essentially no physical evidence that comes down to us unaltered from four billion years ago, so we have to speculate on how life started.

The origin of life is the ultimate chicken and egg problem. On the one hand there’s DNA, the information storing molecule or the genetic code, and on the other hand there are the many proteins that facilitate life’s chemical reactions. The origin of life contains this enigma: How did the complex phenomenon of a working cell get started? Historically the explanation has revolved around DNA because that’s the molecule that serves as the pattern for building proteins. Proteins in turn can form enzymes, which catalyze or facilitate biochemical reactions including the crucial construction of DNA, and thereby is the paradox. Genes require enzymes, but enzymes require genes. Which came first?

Most scientists have focused on DNA, but other life scientists have focused on a concept called “RNA World” which postulates that life began with RNA. RNA, like DNA, is built of chains of molecules called nucleotides. Our understanding of RNA has come a long way since the 1960s when what is called the central dogma of molecular biology held that RNA was just a messenger boy that carried DNA’s information to ribosomes, the cellular factories where proteins get built. In the 1980s biologists realized that not only could RNA transfer information but like proteins it could also process chemicals; it could catalyze reactions. The ability to do both jobs suggested that RNA, and not DNA, could be the primary molecule of life. Much of this work was done by Thomas Cech of the University of Colorado, who won the Nobel Prize in chemistry in 1989 for these insights.

According to the lead scientist of the study under consideration, done by NASA and funded under the Exobiology and Evolutionary Biology program, DNA stores information like a computer hard drive. Niles Lehman, professor of chemistry at Portland State, says, “Beyond that, DNA doesn’t do anything. RNA on the other hand can fold into a 3-D structure that allows it to catalyze a chemical reaction.” Even if RNA can catalyze chemical reactions, in modern cells it gets information from DNA, so how could RNA have been assembled before DNA even existed?
The recent experiments by Lehman and others may have revealed the answer. Individual units or nucleotides of RNA can spontaneously self-assemble. Lehman and his colleagues started their experiments by removing from a bacterium an RNA molecule that works as a self-replicating enzyme. They cut it into chunks, each about fifty nucleotides long, and watched the chunks reassemble themselves into a working enzyme. He said, “We mix the fragments together in salt water at forty-eight degrees, have lunch, come back, and we have self-replicating RNAs in the test tube.” Obviously reassembling an enzyme you’ve stolen from bacteria and then sliced into pieces doesn’t prove that a working enzyme could have formed in the prebiotic world, but there was a method to the apparent madness of Lehman’s experiment. Fifty bases may be a magic number. Lehman quotes chemist James Ferris of Renssalaer Polytechnic Institute who’s been able to string together forty or fifty RNA nucleotides using clay as the catalyst. It’s conceivable that that could have happened in the prebiotic world too.

Summarizing the results these experiments, RNA World begins with three steps: prebiotic synthesis of the individual RNA nucleotides, assembly of intermediate chains, and then final assembly into longer chains. Ferris and Lehman between them have demonstrated steps two and three, but Ferris notes that nobody has yet demonstrated a prebiotic synthesis for individual nucleotide basis from which he constructs the RNA strands. Still, the new results are interesting enough to suggest that RNA can achieve enough complexity to transition from the chemical to the biological realms. The idea that RNA can begin to replicate itself from fragments is very exciting because it identifies the leap in complexity required to kick-start biology.

The astrobiological implications of this work are obvious. The raw materials, the chemical ingredients for life, are known to exist everywhere in the universe, and they will be present on the surface of planets, in many cases with the liquid medium of water available to dissolve them. Once you’ve gone up the first few steps to form fifty base nucleotides, nature and natural processes take over. Life will self-assembly and a replicating molecule will emerge from the chemical mix. If it happened on Earth four billion years ago, it probably could have happened on any similar location. Removing the mystery of the formation of life of Earth will give us a much clearer sense of how often the event can occur elsewhere in the universe.

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