Living in the Universe

Climate Change and Life

Fourth Week of January 2007

Last week I talked about climate change by human hands and the possibility that intelligent civilizations, maybe not even only our own, could cause their own demise through the destruction of a biosphere. This has an important implication for the ability of us to communicate with intelligent civilizations because if they self-destruct on timescales of thousands of years we will be isolated in time and space.

This week saw the publication of research that reminds us that whatever is happening with global warming and climate change now, the episodes of climate change in the geological past are even more extreme. In the mid-Permian era three hundred million years ago, the Earth was in an ice age. Miles thick ice sheets covered much of the southern continent, and the floating ice pack most likely covered the northern polar oceans. A thin band of the tropics were dominated by lush rain forests, which are now preserved as coal beds. Within forty million years all the ice was gone, and the world had turned into a hot, dry place with sparse vegetation and soils that were little more than drifts of wind-blown dust. This rapid transition was marked by dips and rises in carbon dioxide and extreme swings in climate and drastic effects on all the vegetation.

This research was published by lead author Isabelle Montañez, a professor of geology at UC Davis. She cautions that these findings cannot be applied directly to current global warming trends. Montañez and her coauthors derived records of atmospheric carbon dioxide from ancient soils that have been preserved as rocks from coal and from fossils of plants. They extracted a record of sea surface temperatures from the fossils of brachiopod shellfish and looked at the extensive records of past life from fossils of the ancient rainforests. To see how glaciers advanced and retreated they looked at the scars and clues left by the ice sheets that once covered the great southern continent of Gondwanaland which included most of the landmasses of the modern southern hemisphere. Then they put it all into a computer and modeled it.

The new data show that throughout millions of years, atmospheric carbon dioxide levels swung back and forth between two hundred and fifty parts per million, which is close to the present day level, to more than two thousand parts per million. At the same time southern ice sheets retreated as carbon dioxide rose and expanded again when levels fell, a pattern compatible with the idea that greenhouse gases caused the end of the late-Paleozoic ice age. Scientists had assumed that as climate warmed, a tipping point would be reached when the ice sheets would melt rapidly and for good. Instead the new data shows that climate went backwards and forwards between the extremes while the overall change was warming. By two hundred and fifty million years ago the ice sheets were gone. Records of fossil plants show rapid changes in tropical plant communities as the climate changed. On time scales of a few thousand years, lush forests of tree ferns in cool, wet periods alternated with conifers and other plants as they adapted to the harsher and drier climate.

Dramatic swings in climate on timescales of thousands of years, imbedded in even more dramatic changes on timescales of million years, may be quite typical of the Earth’s history. The Permian period of course saw the greatest mass extinction in the history of life on Earth, when ninety to ninety-five percent of all species were extinguished in a short period of time, probably due to dramatic climate change.

A second piece of research also published this week places us in the picture, well not quite us but our precursors. This new paper by researchers from the universities of Yale, Stony Brook, and Winnipeg reconstructs the base of the primate family tree by comparing skeletal and fossil remains representing more than eighty-five modern and extinct species. The team has pushed back the frontier of the early primates ten million years to fifty-six million years ago. They discovered the most primitive primate skeleton ever described.

This two-part study is an extensive evaluation of skeletal structures, and it provides evidence that a group of archaic mammals called plesiadapiforms, once thought to be more closely related to flying lemurs, are in fact the most primitive primates, our ancient ancestors. The team analyzed over a hundred and seventy characteristics of modern primates, tree shrews, and flying lemurs to determine their evolutionary relationships. They used CAT scans to see the invisible structures between the cells and inside the skulls. There are five major features that characterize modern primates: relatively large brains, enhanced vision and eyes that face forward, a specialized ability to leap, nails instead of claws on at least the first toes, and very specialized grasping hands and feet.

Plesiadapiforms have some but not all of these traits. The researchers article argues that these early primates may have acquired the traits over ten million years in small, incremental changes to better exploit their environment. This is fascinating work because it shows that primates, our direct ancestors, have existed almost since the age of the first mammals soon after the death of the dinosaurs in the KT extinction event. Mammals and primates evolved beside each other and our lineage, that includes the strain that now dominates the Earth, started a long time ago.

Climate change is a part of this story too because the development of large brains, which in our biology take about twenty-five percent of our function, and the development of large eyes and acute stereo vision, which occupies a large fraction of our brain capacity, is an important development, but it also makes us fragile. The use of such a large amount of energy for brains and eyes makes us dependent on this energy usage. Energy for brains can’t be used for anything else. It also means that we have to protect our fragile and delicate brains since they cannot survive temperature extremes. In a sense our development and our brain size makes us vulnerable to climate change, and yet our earliest ancestors survived climate fluctuations for over fifty million years to reach our present state.

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Earth’s Doomsday Clock

Third Week of January 2007

Today I want to take on a subject that doesn’t have an obvious relation to astrobiology: climate change. In fact it’s become an unfortunate political hot potato, often bounced around as if it is a red-blue issue. But among working scientists there’s actually very little controversy, and a recent report from the U.N. Intergovernmental Panel on Climate Change has said that it’s more than ninety percent likely that global warming since 1950 has been driven mainly by the buildup of carbon dioxide and other heat trapping greenhouse gases and that more warming and rising sea levels are on the way.

What’s the big difference here with previous reports? Well, first this is an international scientific organization so it represents the opinions of almost all scientists, and second, the shift in language from previous reports, the last one was in 2001, is significant. In 2001 the panel concluded only that there was a sixty-six to ninety percent chance that human activities caused recent warming. The change of moving up to ninety percent is some indication of confidence among scientists that other explanations are not viable. Back in the 1950s and 1960s there was evidence that smoking had something to do with lung cancer, but it wasn’t until the accumulation of medical research that the government decided that it was almost certainly causing lung cancer, with a probability ninety percent or higher in scientific terms, and thereafter putting warning labels on all packets of cigarettes.

Drafts of this new report project a most likely warming of four to eight degrees if the concentration of carbon dioxide in the atmosphere rises to twice the two hundred and eighty parts per million that it averaged for many centuries before the industrial revolution. The concentration now is about three hundred and eighty parts per million, and many climate experts say it would be very difficult to avoid hitting levels of four fifty or five fifty parts per million later this century, given the growth in populations and fuel use and the lack of non-polluting alternatives that can be exploited on a large enough scale to replace fossil fuels.

There’s a lot of activity this year on climate change. The report will be followed by one in April on adaptation, one in May on mitigation, and a final overview in November. There will be a European Union-United States summit in April focusing on energy security and a Group of Eight summit in early June to highlight energy and climate. World Bank economist Nicholas Stern said in October that urgent action on global warming was vital and that delay would multiply the cost twenty times. The Kyoto protocol is the only global pact obliging signatories to cut carbon dioxide emissions. But the United States withdrew from it, and the booming emitters China and India are not signing the treaty. It expires in 2012 and negotiations to find a way forward are sluggish.

In another aspect of this, the Bulletin of Atomic Scientists on Wednesday nudged the world closer to an environmental disaster with their doomsday clock. The doomsday clock has been kept for fifty years since the cold war, when it used to indicate nuclear holocaust and our proximity to blowing ourselves up, but now the doomsday clock also involves annihilation of humans or the destruction of our way of living by environmental catastrophe as well. They moved the clock forward from 11:53 to 11:55, five minutes to midnight and doom. This is the fourth time since the end of the cold war that the clock has been nudged forward. The organization says that the dangers posed by climate change are nearly as dire as those posed forty years ago by nuclear weapons. This Chicago-based organization was founded in 1945 as a newsletter and has since grown into an organization focusing more generally on man-made threats to the survival of human civilization.

Even Stephen Hawking has spoken out on this issue. “As scientists, we understand the dangers of nuclear weapons and their devastating effects, and we’re learning how human activities and technologies are affecting climate systems in ways that may forever change life on Earth,” he said. “As citizens of the world we have a duty to alert the public to the unnecessary risks that we live with every day and to the perils we foresee if governments and societies do not take action now to render nuclear weapons obsolete and to prevent further climate change.”

The Bulletin’s clock has followed the rise and fall of nuclear tensions but now is measuring climate change. The Bulletin’s editor Mark Strauss told the Associated Press, “There’s a realization that we are changing our climate for the worse, and that would have catastrophic effects. Though not nearly as dire as that of nuclear weapons right now, in the long term we are looking at it as a serious threat.”

What’s the astrobiology connection here? The connection is with the Drake equation, the formula astronomers use to calculate the number of intelligent, communicable civilizations elsewhere in the universe. We know that the elements in the planets that can support life are out there in abundance. We also know the universe has provided plenty of time for biology to evolve in different places. But in the Drake equation the likelihood that we are not alone in the universe in terms of communication depends critically on the longevity of communicable civilizations. In other words, how long does any civilization with the technological capability and the space travel ability last? The number of galactic pen pals depends on this time. If the time span is less than a few thousand years, we are operationally alone in the universe because the average distance between civilizations is large enough that no signals can be changed and exchanged before the civilization goes extinct. So a few thousand years is a critical number.

What about us? We’ve had fifty, maybe a hundred years of high levels of technology and space travel. Are we confident we’ll survive a few thousand years in this state to be able to become part of a galactic civilization should it exist? It’s hard to tell, but the future is in our hands. And climate change is indeed an astrobiology issue.

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Killing Life on Mars

Second Week of January 2007

I want to present you with a detective story that took place thirty years ago on the planet Mars. The story was reported at the recent meeting of the American Astronomical Society being held in Seattle. The scientist involved is Dirk Schulze-Makuch, and he has presented the idea that when the Viking probes visited Mars in 1976 and 1977, they may have found alien microbes on the red planet and inadvertently killed them.

That would be extraordinary. What’s the evidence? It’s basically the idea that a more expansive view of where life can take hold and its biochemical basis opens the possibility that these Mars probes were simply looking for the wrong kind of life, because they were looking for life that’s too similar to the Earth’s. In the 1970s the Viking missions apparently found no sign of life, but they were looking for Earth-like life forms in which salt water is the internal liquid of living cells. Given the cold conditions of Mars, life would have evolved on Mars with a key internal fluid consisting of a mix of water and hydrogen peroxide, according to Dr. Schulze-Makuch. That’s because a hydrogen-water peroxide mix stays liquid at very low temperatures, minus seventy degrees Fahrenheit, and doesn’t destroy cells when it freezes. It can suck water vapor out of the air.

The Viking experiments from the 1970s wouldn’t have noticed hydrogen peroxide-based life, and in fact they would have killed it by drowning and overheating the microbes. One Viking experiment seeking life on Mars poured water onto soil that it took into the instrument. That would have essentially drowned the hydrogen peroxide-based life. Another experiment heated the soil to see if something would happen, which would have baked the Martian microbes. The fundamental problem is that we don’t know what life might be like in strange environments, and we’re stuck looking for life the way it is on Earth. It limits our ability to say that life doesn’t exist if it has a different chemical basis.

Dr. Schulze-Makuch even points out that Earth has something related. He points to an Earth bug called a bombardier beetle that releases a boiling hot spray that’s twenty-five percent hydrogen peroxide as a defense weapon. The researcher acknowledges he can’t prove that Martian microbes exist but given the Martian environment and how evolution works, he thinks it makes sense. In recent years scientists have found life on Earth in conditions once thought much too harsh such as in ultra-acidic rivers in Spain and California and ice covered lakes in Antarctica.

Another group working for the National Research Council is looking at the possibilities of extreme life. They’re nicknamed the weird life committee. We won’t ask what they get up to when they’re not on the committee. The group worries that scientists may be too Earth-centric when looking for extraterrestrial life. As Katherine Freeman, one of the reviewers of the NRC work says, “You only find what you’re looking for.” This is a big problem because upcoming Mars missions are built around instruments designed to look for life the way we find it on Earth. Of course, it’s possible that life is similar to Earth and these fears are misguided. Another member of that committee cautioned against just-so stories about what is possible. Either way it’s a fascinating possibility that life on Mars was strange enough that thirty years ago we killed it while looking for life that was like life on Earth.

And a minor side note for this week. I point out that Pluto has been chosen as the 2006 word of the year by the American Dialect Society at its annual meeting on Friday. In this usage, Pluto is a verb and to Pluto is to demote or devalue something, much like what happened to the former planet last year when the general assembly of the International Astronomical Union decided that Pluto didn’t meet its definition of a planet. Society president Cleveland Evans said, “Our members believe the great emotional reaction of the public to the demotion of Pluto shows the importance of Pluto as a name. We may no longer believe in the Roman god Pluto, but we have a personal sense of connection with the former planet.” Plutoed won in a runoff against climate canary which was defined as an organism or species whose poor health or declining numbers hint at a larger environmental catastrophe on the horizon.

The hundred and seventeen year old American Dialect Society comprises linguists, grammarians, historians, and independent scholars. They conduct their vote for fun and not in any official capacity. However, we should note that the society chose truthiness as its top word last year. Truthiness is credited to Comedy Central satirist Steven Colbert who defines it as truth that comes from the gut not books. It took until this year for Time Magazine to declare truthiness the word of the year. So maybe we should pay attention to the American Dialect Society, and maybe we can expect to find the verb Plutoed to work its way into our everyday vocabulary.

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Living in the Universe: Top Ten Stories of 2006

Living in the Universe: Top Ten Stories of 2006

First week of January 2007

In case you are new to the subject of astrobiology or to this blog, I thought I’d start the year by looking back on the previous year and talking about the highlights in this subject of the year 2006. Well, obviously the big highlight would be if we’d found life on another planet. It hasn’t happened yet, folks. As we speak, Earth is still the only planet we know of in the universe. It’s a universe that think is filled with planets and many could harbor life, but we have no evidence yet. But there were some very exciting events of 2006 and I’ll go over my top list of ten in chronological order during the year.

One. Early in the year we witnessed the safe sample return from a comet for the first time with the Stardust mission. A thimble full of comet material returned to Earth representing pristine evidence from the solar system’s formation four and a half billion years ago. Scientists are studying it and learning a lot from it already.

Two. The next story, also in January, was the planet closest in mass to the Earth yet discovered. With over two hundred extrasolar planets known, most of them are Jupiter-sized or larger. This planet, announced in January, is a little more than five times the mass of the Earth, clearly Earth-like although in practice much hotter because of its close orbit to its parent star. It was found by the lensing technique rather than the Doppler technique that most extrasolar planets have been found with.

Three. The following month witnessed some grim news for astrobiology in the NASA budget. Astrobiology was disproportionately cut during NASA’s budget woes, getting a fifty percent cut on its research programs. That was brutal. It put missions like the Terrestrial Planet Finder on indefinite hold, and any chance of going back to Europa and certain Mars missions also took a dive. There’s still big uncertainty hanging over the NASA budget, but there was a popular outcry and even a clamor among scientists who are not astrobiologists to restore some of these cuts and not hurt a program that’s so popular with the public.

Four. In March there was evidence from the Cassini mission of geysers on the tiny world Enceladus, a moon in the outer solar system expected to be tiny and frozen. Only five hundred kilometers across, somehow water is kept liquid under pressure under the surface. The evidence of liquid water so far from the Sun on a tiny moon opens up the possibilities of life because liquid water is one of the key ingredients that life needs.

Five. In April there was an interesting story indicating evidence that the wave of heavy bombardment of meteorites in the first part of the Earth’s history occurred in a narrow window of time only a hundred million years long about 3.9 billion years ago. Since the early evidence of life on Earth precedes this date, there’s a possibility that life got started very early on the Earth and survived the era of heavy bombardment. If biology could have survived that kind of series of impacts, it again indicates how robust life might be in other inhospitable places in the universe.

Six. In June there was an interesting study from Australia of stromatolite colonies, that is bacterial mats, one of the oldest forms of life on the Earth. The study of these types of organisms from 3.5 billion years ago showed that they were amazingly complex, complete ecosystems. The fact that life had such complexity 3.5 billion years ago means complexity developed early, at least in terms of ecosystems even if the individual organisms were rather simple.

Seven. In July, there was evidence of lakes on Titan from Cassini flying by that large moon. These lakes are strange: they have no liquid water, they’re far too cold for that, but instead have ethane and methane, making scientists wonder how strange life might be and could it exist in liquid of this form?

Eight. August saw one of the biggest news stories at least as far as the popular media was concerned: the demotion of Pluto. Well, this is the one I’m least agitated about. Most astronomers consider Pluto an oddball, and for astrobiology it’s a small dead rock. Let’s get over it. In the end, who cares? It’s semantics for the most part. I know that’s an unpopular position with many people.

Nine and ten. In November, a pair of NASA news stories. The big news was that the shuttle will fly to fix the Hubble Space Telescope. That’s good for all astronomy, not just astrobiology. This followed on the successful shuttle flight from July 4 of also 2006. And the final story of the year, only a few weeks ago in December and probably the most important story, was the discovery that water on Mars has flowed recently. Images taken only a few years apart by the Mars Global Surveyor, now a defunct mission, showed that water has flowed. Changes in the topography on timescales of only a few years indicate that water erupts onto the surface, almost immediately evaporating or freezing. But such recent activity and the indication that water can exist onto the surface of Mars is very exciting and increases the suspense and the tension of going to Mars with more sophisticated instruments to try and find subterranean microbial life forms.

After I pulled this list together I ran across the list compiled by NASA’s Astrobiology Magazine, so I quote that for comparison, and there’s a fair amount of overlap. They ordered their stories by importance. According to NASA the tenth most popular story or most important story was the end of the Mars Global Surveyor, one of Mars’ most successful missions over the years. Number nine was the launch of the New Horizons mission to Pluto which will take almost a decade to reach that frozen planet, well, not even a planet now we know. Number eight was the arrival of ESA’s Venus Express at the planet Venus and the beginning of its large survey program. Number seven was Cassini’s continuing investigations of Saturn’s moon Titan with many interesting discoveries coming almost weekly. Number six was the discovery of a super icy Earth, a planet weighing thirteen times as much as the Earth, one of now over 200 extrasolar planets known. The number five story was the continuing mission of the Mars Exploration Rovers. They had their mandate and their budget renewed for a third time. The rovers have been extraordinarily successful and very popular with the public. You can follow their daily progress on NASA’s website. The number four story was the Mars Reconnaissance Orbiter which went into a stable orbit around Mars and started to send back stunningly detailed images of rocks as small as a small boulder, a meter across. This will map out Mars to make safe landing sites for the next series of missions that will land there. The third most popular story was the discovery of liquid water on Saturn’s icy moon Enceladus, probably broadening the diversity of solar system environments where there may be conditions hospitable to life. The second story was the collection by Stardust of particles from the comet Wild 2. And the top story, and I’m in agreement here, was the discovery of possible water flows on the surface of Mars within the past few years, really increasing the potential of microbial life on our near neighbor.

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