Monday, December 20, 2010

Stem Cells in Microgravity

One interesting and recent study on human embryonic stem cells experiencing net microgravity sheds some insight into what may be causing long lasting health problems for astronauts. Researchers at the University of New South Wales in Australia placed stem cells in a rotating machine developed by NASA that introduces a net gravity close to 0g. The stem cells were in the machine for 28 days, while the control group of stem cells was maintained in the exact same nourishing conditions while experiencing normal Earth gravity conditions. After the experiment, the cells showed several differences at the molecular layer. Nearly 64% of proteins in the microgravity group differed from those grown under normal gravity. In the microgravity treated stem cells, there was more expression of proteins that degrade bone and there was less expression of proteins with antioxidant effects. Additionally, proteins involved in cell division, the immune system, the muscle and skeletal systems, calcium levels within cells, and cell motility were also affected in this group.

These results suggest that microgravity conditions directly impact the development of stem cells in the human body. Human embryonic stem cells can develop into any cell type, and they play a role in repair of damaged tissue and in the maintenance of the normal regeneration of organs with the potential to regenerate. With this importance, if experiencing microgravity hinders their development, then long-term space travel poses serious threats to the health of astronauts. Research is currently being done on several differentiated cell types to determine if the molecular changes are more widespread, and these experiments will also take place on future missions into space in order to verify that these results are also seen in true microgravity, as opposed to net microgravity. Another implication of these results is that future research should be directed towards biomedical interventions that prevent these changes in protein expression.

Yet another implication of this study that concerns long-term survival during space travel is the complications that might arise during procreation. If cells do rely on gravity for some sort of mechanical feedback, then the development of an embryo in microgravity could prove to be impossible. Thus, if humans plan to make long distance trips to other planets in our solar system, the issue of genetically engineering human bodies for them to survive procreation in space might be a necessary step in future.

Wednesday, December 15, 2010

Microbialites (One more blog that I forgot to publish...)

A couple weeks ago, I gave a presentation on microbialites for our lesson on extremophiles. I chose to talk about microbialites because I’d never heard of them before, and because there’s been a lot of exciting research going on over the past few years regarding the potential for microbialites to serve as potential biosignatures for life on Mars.

Basically, microbialites are nothing more than organic sedimentary mineral deposits that are covered by a thin layer of microbes that become entombed in the mounds as they grow outwards. The difference between stromatolites and microbialites is that stromatolites are the Earth’s oldest known structure and show no direct evidence of life, whereas microbialites are relatively young in geological terms, as they are only about 12,000 years old. The reason that scientists are getting so excited about them is because they serve as macroscopic evidence of microscopic life. Chris McKay, a scientist with the NASA Astrobiology Institute, regarded microbialites as:

“They are helping us understand one of the big astrobiology questions how early life took hold and began to flourish on Earth, These fossils are like seeing a billion-year-old footprint in the sand and comparing it to a modern foot.”

NASA scientists realized the importance of microbialites over a decade ago, and began studying the ones that are growing in Pavillion Lake in British Columbia in 1998. The microbialites were formed layer after layer with the oldest lying on the bottom, thus the structure provides a record of growth and also yields important clues about the organisms that once lived there. In 2008, NASA researchers reported that the microbialites in Pavillion Lake were composed of calcium carbonate, ranging in size from small bumps just a few centimeters across to enormous structures as large as 12 feet high. Additionally, they came in a variety of vegetable-shapes: some were described as resembling cauliflower, other like broccoli, other like asparagus, and some like carrots.

How these "veggie"-microbialites came to be placed in this lake isn’t completely known. As of last year, scientists are sticking with the hypothesis that bacteria were involved in some way in creating the large structures. However, it's possible that the only role bacteria had was in the formation of the crusts on the surfaces of the structures, but the structures themselves are the products of a purely chemical, rather than biological, process.

Some cyanobacteria excrete calcium carbonate, so one possibility is that the crusts are composed of this bacterial waste. Another is that the bacteria built up an electric charge along their cell walls, which attracted the calcium carbonate in the lake water. Or maybe the cyanobacteria secreted slime that the carbonates bound to.

In other places around the world, Cyanobacteria are famous for building a variety of structures, from thick rubbery mats to the layered dome-like structures we know as stromatolites.Today, though, they are rare, existing only in extreme environments.
The shallow waters of Shark’s Bay, in Western Australia, for example, are home to large fields of dome-shaped stromatolites. But Shark’s Bay is too salty for the tiny worms that like to snack on the bacteria. That’s why the stromatolites can thrive: there’s nothing around to eat them.

Pavilion Lake, however, is “normal.” It has all kinds of larger organisms living in it. It’s even stocked with fish. This is what creates the mystery.

So, researchers are approaching this topic from a variety of different angles. Some of them are looking at the chemistry of the lake water to understand it's topography and underground water sources; and others are doing DNA analysis of the slime that coats the microbialites to figure out which organisms are living there, what they're eating, and what they're excreting. Still other researchers are comparing the carbon in calcium-carbonate samples from the slime layer to carbon from the core of the structures to see if there is a clear biological mark in the core. The basis behind performing this investigation is that living organisms generally use the lighter C-12 isotope, leaving behind the heavier C-13 isotope.

So far the research has been largely inconclusive. The carbonate in the surface communities have a signature of biological activity, however deeper down, the signature doesn't appear to be preserved. This is contradictory to what you would expect since if the structures were built by microorganisms, there should at least be some isotopic evidence of their biological origin. Though, there is a possibility that over time, the structures have dissolved and re-crystallized, and in the process of doing this, changed from one form of calcium carbonate to another, thus losing their biological carbon-isotope signature.

If this avenue of research turns up supportive findings, the results could provide new insight into how biosignatures are modified and preserved over time, which could aid in future efforts to for biosignatures on Mars.

Monday, December 13, 2010

How science fiction can inform Astrobiology: The recap of a discussion with Jeffrey A. Carver

Yesterday we met with science fiction writer, Jeffrey A. Carver. He was extremely welcoming and helpful in explaining to us much about science fiction, writing, and the intersections of these topics with astrobiology. The reason that we felt science fiction would be an interesting topic to discuss in astrobiology is that science fiction deals with the imaginative, which astrobiology lacks. Astrobiology seeks to understand where life could live, what it could look like, and how we could find it, however, this is intentionally limited by our current technology and scientific knowledge. Astrobiologists use science to try to figure out the same things that science fiction writers imagine. While fantasy imagines the impossible, science fiction narrates the possible.

Astrobiologists may say that much of science fiction is unfeasible, however, science fiction does function within the loose (or even strict) boundaries of science. For instance, NASA scientist Geoffrey A Landis, writes with a very strong science background and even works in the cutting edge of space research. There are other authors that are biologists, physicists, etc. and authors who merely have an interest in science and not a degree, that meld their imaginative stories with science.

Science fiction writers focus on the imaginative aspect of extraterrestrial life and space travel down and this perspective is interesting for astrobiology to take into account. There are new technologies and discoveries that have first been described by science fiction writers. A great example is Arthur C Clarke who imagined geostationary satellites, a global library and light rails well before they were developed. In fact, scientists have gone so far as to test the plausibility of space stations and artificial worlds described in science fiction. Clearly there is some overlap in our imagination and the expansion of the limits of science.

The existence of SETI provides evidence of the overlap between science fiction and astrobiology because the use of SETI to ‘find intelligent life’ suggests that there are sentient beings elsewhere in the universe that will be able to communicate in a manner that we understand and whom would want to communicate with us. This is not much more ‘realistic’ than what we find in science fiction. Indeed, some other ideas in science fiction like cloning, cryogenic suspension, and living on the moon are active areas of research (well, living on the moon was at least at some point an active scientific interest). Clearly, science fiction is not totally unfeasible—animals have been cloned and human bodies frozen after death. Science has just not been able to keep up with the imagination and these technologies are not as practical or useful as they appear in science fiction. New areas of research can even be described as ‘science-fiction-y’ such as the creation of a microbe using artificially produced DNA in the spring of 2010.

Scientists in general, are very skeptical and it is not within the discipline of science to imagine things that are far beyond what we already regard as fact or which are beyond what we can understand using current technology. Thus, astrobiologists do not need to believe that the worlds that appear in science fiction are possible, they just need to understand that science is a human endeavor, and because of this, science may be held back by our imagination. There are many topics in astrobiology that would have seemed far-fetched just a couple decades ago, like the idea of a biocentric universe-- that our cosmology and metaphysics cannot ignore the important interplay between conscious observers and quantum effects—and the two-slit experiment. Though science fiction writers may push the boundaries of the feasible at times, the feasible is a human-centric notion bounded by science. We don’t know what is feasible or not and taking a hint from science fiction writers and expanding our imagination of what life could look like and where it could live is an interesting thought experiment for astrobiology.

Monday, November 15, 2010

Alternatives to RNA from NAI videocon

For this blog entry I wanted to write about one of the talks from the NAI Workshop that I saw on Monday given by Ram Krishnamurty from the Scripps Research Institute on his research into structural alternatives for RNA. The basic motivation of his research is to study the potential of novel oligomer systems to act as informational systems similar to RNA. One of the major goals of Krishnamurty’s team is to systematically synthesize, by chemical methods, potentially self-replicating chemical systems that may have been competitors to RNA in a primordial world. At the conference he presented a system he recently synthesized in which he expected the strands of the molecule to pair well with DNA and RNA as well as with its partner; however, some of the strands failed to bind which led to the discovery an additional criterion for strands that may shed light on why RNA prevailed in the primordial world.

So far this semester, it has come up a lot that before the rise of DNA, RNA acted alone in propagating primitive life. We’ve also explored the idea that, in such an “RNA World”, there would be a fundamental necessity of RNA to act as both a transmitter of information and catalyst of life-sustaining reactions. However, even years of research, the potential for RNA to self-assemble under what are thought to be likely primordial conditions still hasn’t been demonstrated.

In the talk, Krishnamurty presented results they have discovered recently regarding the chemical nature of pre-biotic RNA. The work focused on two pair of oligomers with the diamino and dioxo forms of triazines, and the diamino and dioxo forms of pyrmidines acting as alternative bases. The expectation was that the diamino and dioxo forms of each would exhibit Watson-Crick base pairing, and that the compounds would also bond well with RNA and DNA. It turned out that the diamino triazine paired strongly with RNA and DNA, as expected, but the diaxo triazine paired very weakly. This was strange, but even stranger was that the observations for the pyrmidines was opposite: the dioxo paired strongly, and the diamino paired weakly. This lead to the discovery of a remarkable correlation between whether the base in a synthesized compound bonded will with RNA and DNA or its pair, and the value of its acid dissociation constant (pKa). These results suggest that a base with a pKa value close to that of the base it is to pair with will have weak, if any, bonding, while the team found strong bonding among bases with high differences among their pKa values.

So, the ultimate conclusion of his talk was that the optimal strength of bonding between bases is literally responsible for life as we know it. Bonding that is too weak would prevent self-replication from proceeding, while bonding that was too strong might do the same, because double strands would become too difficult to separate. RNA and DNA exhibit an optimum base pairing strength, and understanding the reasons why are critical to understanding how they arose.

So, Ram and his team initially set out to identify potential RNA alternatives, but what they found was a very interesting new criterion to better understand RNA and DNA and further the search for alternatives or precursors. The pKa itself may not be responsible for the relative bonding strengths of different bases, the results do suggest that pKa differences are a good and relativle convenient indicator for potential bases that will have the proper bonding strength. An interesting time is upon us, where pKa may now be one of the first considerations in work to identify alternative bases.

Saturday, November 13, 2010

Dead on Arrival

By now, we're all familiar with panspermia or more accurately exogenesis--the hypothetical scenario in which life was "deposited" onto Earth by some kind of asteroid or collision early on.

An argument occasionally arises against this idea, supposing that radiation would cause anything but the toughest extremophiles to be damaged beyond repair. There is the emerging idea that genetic material could still be recovered from damaged (read: dead) biological molecules and be used as a sort of springboard for life to develop.

Paul S. Wesson's new paper in Space Science Reviews talks about his theory of "necropanspermia", which isn't nearly as supernatural and awesome as it sounds, but it does bring up a lot of interesting questions about how life gets around in outer space, if it does at all.

Wesson encourages his peers to focus not on the question of "alive or dead" but "the question of genetic information". He argues that "random chemical interactions cannot produce the genetic information" present on Earth right now. He demonstrates by using a model of a prebiotic Earth with a given amount of amino acids. He then goes on to say that the "molecular interactions" that would follow would take 500x10^6 years to create 194 bits of information. For comparison, he gives e. coli: 6x10^6 bits, and a typical virus: 1.2x10^5 bits. So, he posits two possible conclusions. Either, life began on Earth under a directed, not random, sequence of chemical interactions, or it was a large amount of genetic information that was deposited here very early on. Wesson sides with the second camp. "Natural processes do not account for the genomes of observed organisms," he says.

He does, however, admit "that all versions of panspermia suffer from a hole in our knowledge, concerning how to go from an astrophysically-delivered entity which contains substantial information to one which has the characteristics of what we normally regard as life."

So his point is basically that viruses are great candidates to be used as a vessel for genetic information, since that's basically what they are.

One of the biggest detractors is Rocco Mancinelli, who quipped that "once you're dead, you're dead." He studies extremophiles for a living and what needs to go on in an environment to sustain life. I tend to agree with his take on the issue, as he points out that Wesson has missed a few drawbacks to his theory--essentially, that there are more dangers out there than he's led us on to.

Mancinelli mentions potassium decay (over the course of a long period of time in space: very damaging) and dessication, when hydrogen and hydroxyl molecules separate from the cells and form water, which serves to "denature" proteins, forcing them to recombine and lose functionality.


Wednesday, November 10, 2010

Methane on Mars

This is an interesting twist on the view that Mars is a dead planet. A recent six-year study of methane levels in Mars' atmosphere shows the planet is actually far from dead, but whether the activity is merely geological or microbial is still unknown.

A team of researchers based in Italy looked at billions of measurements taken by NASA's Mars Gobal Surveyor to compile seasonal maps of methane gas, which appears in minute quantities in the carbon-dioxide rich atmosphere. The researchers found that methane concentrations are highest in autumn and drop off dramatically in winter. Levels build up again in spring and climb rapidly in summer, which causes the gas to spread across the planet.

Ultraviolet light from the sun breaks methane down, so something is happening either on or in the planet that is replenishing the gas. Also, another mystery is the speed at which methane is being depleted. The seasonal changes are quite unexpected from a planet that is believed to not have much left going on.

Researchers found three regions in the planet's northern hemisphere with consistently higher concentrations of methaneTharsis, Elysium, and Arabia Terrae. The first two are home to the largest volcanoes on Mars, while Arabia Terrae has large quantities of subterranean frozen water.

Lead researcher Sergio Fonti, from Italy's Universita del Salento, says the seasonal nature of the methane levels rules out the possibility of cosmic ray bombardment or meteorite impacts causing the changes. "It could be geology or biology, but it is not coming from another source," claimed Fonti.

On Earth, colonies of bacteria that consume methane have been found living right along species that produce it, and many scientists believe that there could easily be a similar situation on Mars. Still, some skeptics believe that some simple geologic explanation such as the release of methane trapped in frozen water during seasonal melting could help explain the phenomena.

NASA and Europe are planning a joint mission in 2016 to draft more detailed maps of Mars' methane. NASA's Mars Science Laboratory, scheduled for launch next year, also has an instrument that will detect atmospheric methane.


Helping Plants Move onto Land

At the University of Sheffield, a group of scientists is making advances on learning how the Earth's first plants moved onto land over 470 million years ago. Their breakthrough: soil fungi.

The research provides some missing evidence that an ancient plant group formed a partnership with soil-dwelling fungi to help spread green plants across the land nearly 500 million years ago. Several groups provided input to the research, including the Royal Botanical Gardens, Kew, Imperial College London and the University of Sydney. The evidence sheds some light on the evolving relationship between the Earth's land plants and fungi.

It has been suspected that soil fungi played an essential role in assisting early land plants colonize terrestrial environments by forming mutually beneficial relationships, but there has been no evidence demonstrating how this worked. To show exactly how this happened, the team studied a thalloid liverwort plant (below), which is among the most ancient of land plants that still exists and also shares many traits with its original ancestors.

These plants were placed in controlled-environment growth rooms that simulated the conditions of the Palaeozoic era, which is when the plants were believed to have originated. Under these conditions, the benefits of the fungi for the plant's growth were significantly amplified and this favored the early association between the plant and its fungal partners. When the thalloid liverwort was colonized by fungi, its photosynthetic carbon uptake, growth, and asexual reproduction were all significantly enhanced. These factors have a clear beneficial impact on the plant's fitness.

Why does this happen? The fungi provide the plants with essential soil nutrients. This helps them grow and reproduce better, and in exchange, the fungi benefit by receiving carbon from the plants. This symbiotic relationship resulted in each individual plant being colonized by fungi that could take up the area of 1-2 times that of a tennis court.

Again, this idea has been floating around for a while, but this group was the first to provide hard evidence of the process. Professor David Beerling, from the University of Sheffield, said that "[this] shows that plants didn't get a toe-hold on land without teaming up with fungi. ... [This] will require us to think again about the crucial role of cooperation between organisms that drove fundamental changes in the ecology of our planet." This is true, and given that fungi inhabit every type of habitat in the world, it would be interesting to see if there are any other of these associations that may have shaped the Earth as we know it.

Sunday, November 7, 2010

We Had Water the Entire Time?

This isn't an actual entry, but some (very) recent news about the origins of water on Earth before we get too far away from that topic in class.

Apparently, we may have had water from day one. This makes a lot of sense, since I was at one point talking about the discrepancies between the D/H ratio of comets and our ocean (my last presentation, I think).

Friday, November 5, 2010

Zircon Dating: Hadean not so Hadean?

This will include no advice about pursuing a relationship with a mineral.

But it will include some hypotheses on early environmental makeup with the help of half-lives and Australia. In the form of zircons.

So a little bit of background on atmospheric origins: two of the leading theories on how our atmosphere formed that I've found: planetary degassing and comet impact. One of the flaws with the latter are that the D/H (deuterium/hydrogen) ratios of comets that we've studied do not match the D/H of our own planet--Hale-Bopp for one--which reinforces the idea that, while it is possible that some of the responsibility may fall to comets, it can't only come from comets.

What is less known about the atmosphere's formation is the question of when? This is where zircon comes to the rescue.

Deep in the heart of Jack Hills in Western Australia lies some of the oldest pieces of zircon that can give us a hint about the age of our atmosphere. Through measurements utilizing uranium decay (into lead) and the measurements of temperature related to titanium composition, zircons suggest a different Hadean eon.

"For example, oxygen isotope compositions of these ancient zircons suggest the presence of a terrestrial hydrosphere and stable continents only 200 Myr after accretion (Mojzsis et al. 2001)."

The composition of the zircons gives us evidence of the type of environment they were in when they formed, hinting that--since these zircons are in the range of 4.2-4.4 billion years old--the very early Earth had a burgeoning atmosphere.

"Excesses of 129Xe in mantle-derived samples relative to the atmosphere have been interpreted to indicate the presence of live parent 129I in the deep Earth following early degassing of the atmosphere (e.g., Staudacher and Allegre 1982; Allegre et al. 1983) since 129I decays to 129Xe with a half life (t1/2) of only 16 million years. If true, then it is argued that the present atmosphere and hydrosphere must have formed by ~4.4 Gyr (Podosek 1970)."

This posits a different way of dating zircons--not by uranium and lead, but with xenon and iodine, giving further evidence to an earlier-than-though atmosphere.

Lunine textbook

Indestructible Bears

The image to your right might look crazy scary, but that creature is less than a millimeter--and probably poses no threat to humankind whatsoever, which is great, since they're nigh invulnerable.

What this is is the tardigrade, affectionately called "water bears" by some people for their similarities to our mammal friends and their love of water. They find their home on various types of moss, and they're far from uncommon. What is uncommon is their survival mechanism. They need water to stay active, so when it's gone, it is then that they enter a state of "suspended animation" causing them to be able to live without water for over a decade. In this state, they're able to endure intense heat (over 90 degrees celsius) and intense cold (near to absolute zero). Couple that with a strong shield against radiation, and you have a creature that could easily be counted as one of the strongest organisms on Earth.

So, it's pretty great that we've found such a crazy strong organism with a cute name and ironic strengths, but what can we learn from them? Or with them?

Their defense against radiation is particularly interesting, since radiation causes severe damage to DNA. Somehow, these tardigrades don't flinch at this. Proteins will help re-form its integrity, and its own defenses also help. Radiation resistance isn't a tardigrade-exclusive skill. Many extremophiles live in places with extreme radiation levels--caused by uranium-rich granite and radon gas. They've also developed systems in place to repair their DNA and shield a good portion of the radiation.

What is also fascinating about the tardigrades are what scientists have been testing it with, such as acetonitrile, a dissolving chemical present on Titan, as well as possibilities of survival on Mars. Of course, this idea of tardigrades living in these places is slim, since their suspended state would be the only state they could survive in.

Another feat the bears can do is completely dehydrate themselves--a bit confusing considering their name, but altogether astonishing when you consider them as living things literally frozen in this state where they thrive off of nothing.

The creatures are clearly impressive and could hold a lot of clues for human protection against radiation and other forms of astronomical injury--they're able to take a dose of radiation that's 4000 times the strength of a harmful dose for humans. Recent research put them in low Earth orbit, exposed to the extreme conditions of space, and most of them survived, and those that survived could even reproduce.

Saturday, October 30, 2010

The hunt for extremophiles in Lake Untersee

In early 2008, a team of NASA scientists left the United States for Antarctica to explore one of the strangest lakes on our planet: Lake Untersee. This body of water is fed by glaciers and permanently shielded by an ice layer, however, what makes it particularly interesting to scientists is its basicity. Lake Untersee is extremely alkaline, with a pH comparable to that of extra-strength laundry detergent. Additionally, the lake’s sediments produce more methane than any other natural body of water on Earth, and thus, if life in any form is found in these waters, the implications will be unbelievable. This should sound familiar to us: Predominantly icy areas? The presence of liquid methane? These are the exact same sort of characteristics possessed by the exotic planets that we talked about in class a couple weeks ago. The icy moons of Jupiter (Europa, Io) and Saturn (Titan, Enceladus), Mars, and Venus are for the most part, cold, methane-rich places where the potential for life has been visited over the years.

Anyway, these NASA researchers are going to Lake Untersee with the intent to search for extremophiles – tough microbes that thrive in conditions that are often considered to be too extreme for most other living things.

Richard Hoover, expedition leader of NASA’s Marshall Space Flight Center, notes that in recent years researchers have begun to realize that “Goldilocks zones” that contain what we consider to be perfect temperature and pH aren’t necessarily imperative for the existence of life. Researchers have found microbes in ice, boiling water, and even nuclear reactors – these extremophiles that were once considered to be oddities, may be the norm elsewhere in the cosmos. Of the expedition Hoover said:

With our research this year, we hope to identify some new limits for life in terms of temperature and pH levels. This will help us decide where to search for life on other planets and how to recognize alien life if we actually find it.”

What I found to be the most interesting discovery of Hoover’s expedition though, was the phenomenon of the “ice geyser” that the researchers discovered when they triggered one by drilling into a localized pocket of high pressure air in the upper layer of the ice sheet that covered Lake Untersee. This phenomenon may be pertinent to the recently discovered “ice geysers’ that erupt from the cracks in the “tiger strip” area of Enceladus. The ice bubbles that were found throughout the surface of Lake Untersee were also observed (by high-resolution dark field microscopy) to contain motile bacteria. The presence of viable bacteria frozen in the ice of this body of water suggests that maybe it isn’t completely necessary to drill through the thick icy crusts to search for life in the seas of the frozen moons of Jupiter and Saturn – viable cells may be cryptopreserved in the upper layers of the ice crust!

Thus, from this we learn that complex robots and machinery need not be capable of drilling down thousands of feet beneath the surface of these icy lakes and risk degradation by extreme conditions. They really only need to be able to drill down several hundred feet in order to encounter one of these ice bubbles in which life forms may have the potentially been preserved.

The Limits to the Habitability of Water

Water is vital for life as we know it and is one of the key factors we associate with habitability and look for in search of life elsewhere in the universe. But not all water has life living in it. Researching extreme environments has helped to distinguish the limits of what constitutes habitable water conditions on our planet, which could help us determine what types of water are more likely to contain life on other planets. This suggests that the principle of looking for water in order to find life may need to be refined because not all water is habitable.

On Earth, we know that life can survive in a wide variety of water temperatures and pressures, and yet there are watery places where no living things have been found.
Scientists have found that only 12 percent of the volume of the Earth where liquid water exists is known to host life. The remaining fraction of liquid water seems strictly uninhabitable – both here and possibly on other distant worlds. Although this is just taking into consideration the ability of our life form to live in these type of watery environments, not other alien life forms.

Although we typically think of water being liquid between zero and 100 degrees Celsius, this is only true for pure water at Earth’s sea level atmospheric pressure. If salt is present, water's freezing point drops below zero degrees and its boiling point rises above 100 degrees. At high pressure, as well, water remains liquid above 100 degrees Celsius. In fact, the authors estimate that liquid water can exist to a maximum depth of 75 kilometers below the Earth's surface, where the temperature is more than 400 degrees Celsius and the pressure is 30,000 times that at the surface.
Conditions on Earth do not allow liquid water below a depth of about 75 km, which leaves a thin outer shell where liquid water can exist. This means that out of the entire Earth volume, 3.3 percent has the right conditions for liquid water but only 0.2% has the potential for habitable water.

The highest temperature known to support life--an Archaea named "Strain 121"--is 121 degrees Celsius. Some biologists believe organisms might survive at even higher temperatures, but nothing has broken the record yet. This means that the upper bound of habitable water, in terms of temperature, is about 121 degrees. At the other end of the thermometer, liquid water can be found on Earth at 89 degrees below zero in thin films, however, the coldest water temperature known to support active life is 20 degrees below zero, which is what the researchers take as their lower habitable boundary.

In terms of pressure limits, life has been found as far down as 5.3 km below the surface, where the pressure is 1500 times that at the surface. No one has yet dug deeper in search of life so we are not sure if life can survive in higher pressures than this. As for low pressure, life has been found high up in the atmosphere where the air is thin, but these microorganisms are typically dormant and are only revived when given the necessary nutrients. The authors therefore take the low pressure limit for active life to be one third of atmospheric pressure, which corresponds to the altitude at the top of Mt. Everest.

Biosphere limits

According to the above limits, life on our planet is restricted to a thin shell that roughly extends from 10 kilometers above the surface down to 5 kilometers below (or to depths of 10 kilometers in the ocean). This leaves uninhabited 88% of the volume where water exists on Earth which suggests that life and water are not equivalent and there seems to be a lot of water present that is hostile to life.

What is even more interesting is that nearly all of Earth's liquid water is located in habitable regions, so that only a small fraction of the water conditions on Earth are friendly to life. But this is slightly misleading because the only truly constraining factor in this analysis is the observation that life apparently can't survive above 122 degrees Celsius.

What does this mean for water on Mars?

Jones and Lineweaver are currently modeling the crust, mantle and core of Mars and using heat flow estimates to construct a Martian water phase diagram, like the one they made for Earth's water. The results will show at what depths potentially habitable water (as defined by the current study) might be found on Mars.

This sort of "habitable water" analysis could also be used for the liquid oceans that are thought to lie beneath the icy crusts of Jupiter’s moon Europa and Saturn’s moon Enceladus. And it may help characterize exoplanets for which a reasonable phase diagram can be estimated.

This may halp us focus our search for life. It also adds complexity to the idea that water and habitability are equivalent.

Another interesting point is that there may be more to the inhabitability of water besides just pressure and temperature. Perhaps there are regions that are too salty? or too high in certain chemicals? or too polluted?

One related recent discovery is that of methane-eating bacteria at "Lost Hammer":
there have been microbes found that live in water that is so salty it is liquid at subzero temperatures, contains no consumable oxygen, and has high amounts of bubbling methane. This spring is located in a highly unique spring--Lost Hammer--on Axel Heiberg Island in Canada's extreme North. Despite these incredibly harsh conditions, researchers from the McGill University have found life. This life consists of methane-consuming bacteria.

They were surprised not to find methanogenic bacteria that produce methane but instead to find these very unique anaerobic organisms that survive by essentially eating methane and probably breathing sulfate instead of oxygen. "The point of the research is that it doesn't matter where the methane is coming from," Whyte explained. "If you have a situation where you have very cold salty water, it could potentially support a microbial community, even in that extreme harsh environment."

It has been very recently discovered that there is methane and frozen water on Mars. Photos taken by the Mars Orbiter show the formation of new gullies, but no one knows what is forming them. One answer is that there could be that there are springs like Lost Hammer on Mars. There are places on Mars where the temperature reaches relatively warm -10 to 0 degrees and perhaps even above 0ºC and on Axel Heiberg it gets down to -50, easy. The Lost Hammer spring is the most extreme subzero and salty environment we've found and provides a model of how a methane seep could form in a frozen world like Mars, providing a potential mechanism for the recently discovered Martian methane plumes.

How has the moon impacted life on Earth?

If we condense the time of Earth’s existence into 24 hours, the moon would form just 10 minutes after the Earth was born. The Earth formed 4.56 billion years ago, and the Moon formed about 30 million years later. An impactor about the size of Mars struck the Earth at an oblique angle, and removed some of the magmatic mantle which was put in orbit around the Earth, together with some of the debris from the impactor itself, and this material eventually formed the Moon.

The tidal effect of a body increases as a cube of the distance, so the effect of the Moon’s tidal forcing on the Earth was extremely high at this time and provided some additional energy to the heating from radioactive elements present. As Earth started to cool, the Moon still was a source of heating that may have had some geological effect, keeping the Earth’s magma hot and perhaps forcing additional convection in the Earth’s mantle. With further cooling, the first crust started to float on top of the magma. During this period the Earth was subjected to increased meteor bombardment. Many of the large basins on the Moon are evidence of this late heavy bombardment. In this way, the Moon is a history book for the inner solar system and the Earth.

The usefulness of the moon for learning about early Earth:

The Earth was hit more often than the Moon because Earth is larger and has more gravity. When some of these impactors hit the Earth, the explosion caused some rocks and dirt from Earth to shoot up and land on the Moon. There is potentially a LOT of material from early Earth buried beneath the surface of the moon--up to a few hundred kilograms of Earth material per square kilometer of the Moon’s surface. It would be very interesting to dig this material up and sample these rocks from early Earth because almost nothing from this time period has survived on the Earth tiself. This is because of tectonic recycling of the crust plates and atmospheric weathering. We would try to detect some organics within those rocks, and that could tell us about the history of organic chemistry on Earth. Some of these rocks could even have preserved fossils of life. Such rocks could help us look further back into the fossil record, which now stops at 3.5 billion years ago. This way, we could possibly learn about the emergence of life on Earth.

By exploring the Moon, we also can get clues on how the Earth has evolved. We can study processes on the Moon that have also shaped the Earth, like volcanism and tectonics. Because the Moon is smaller than the Earth, the Moon’s radiogenic heating dissipated much faster. Because the Moon offers different conditions than the Earth, we can better understand how physical processes work generally by studying a larger range of parameters than just the Earth’s.

Lunar effects other than tides:

There are people who propose that the tidal effect of the Moon may have helped trigger the convection on the Earth that led to the multi-plate tectonics. The other planets don’t have the same tectonic cycle. For most of them, the crust is like a lid that doesn’t move much horizontally, and the magma and heat are blocked by this lid on the surface. The Earth instead has rolling convective motion that drags the crust, and then the crust plunges back down into the mantle and gets recycled.

There are some very subtle effects of the Moon in the climate and the oceans. One pattern that has been found recently is related to the El Niño phenomenon. You have a cold undersea current coming from the Antarctic sea, and that creates the Humboldt stream which keeps the sea around the South American coast near Peru and Chile quite cold. Because of this, there are fewer clouds and less precipitation there. Sometimes this current drifts away from the coast, and then you have much more cloud formation and a period of very bad weather over South America which we call El Nino. People have connected some newly discovered streams with how the Moon’s tidal effect influences the mixing of the deep ocean. If you took away the Moon suddenly, it would change the global altitude of the ocean. Right now there is a distortion which is elongated around the equator, so if we didn’t have this effect, suddenly a lot of water would be redistributed toward the polar regions.

In addition, the Moon has been a stabilizing factor for the axis of rotation of the Earth and thus has contributed to the maintenance of a stable climate. Mars, in contrast to Earth, has wobbled quite dramatically on its axis over time due to the gravitational influence of all the other planets in the solar system. Because of this obliquity change, the ice that is now at the poles on Mars would sometimes drift to the equator. But the moon has helped stabilize our planet so that its axis of rotation stays in the same direction and consequently, we had much less climatic change than if we had no moon. And this has changed the way life evolved on Earth, allowing for the emergence of more complex multi-cellular organisms compared to a planet where drastic climatic change would allow only small, robust organisms to survive.

We know that the Moon has influenced biology because of tides, but it has had other influences on biology, as well. For instance, the eyesight of many mammals is sensitive to moonlight and the level of adaptation of night vision would be very different without the Moon. Thus the moon has influenced evolution in this respect.
Human vision is so sensitive that we are almost able to work by the light of the Milky Way. The full Moon has more light than we need to see at night. For most of our history, we were hunting and fishing or doing agriculture, and we organized our lives by using the Moon. It determined the time for hunting, or the time where we could harvest. That’s why most of our calendars are based on the Moon and there are many examples of human behavior that may have been based on lunar phases.

Studying the Moon helped us determine distances in the solar system and the size of celestial objects. By studying lunar phases, for example, people were able to determine how far the Moon is from the Earth, the size of the Earth, and our distance from the sun. The Moon has inspired humankind to learn how to travel to space, and to bring life beyond Earth’s cradle.

Understanding the influences of the moon on life on Earth is important for recognizing the importance of moons to life in general. If moons are deemed necessary for life, then the search for life can be further narrowed to only planets with moons. Is the moon essential for life on Earth? I am not sure. But there are many helpful influences of the moon on Earth. The one that seems particularly interesting (besides tides which i discussed in an earlier blog) is that of the moon's role in the stabilization of Earth's rotation around its axis. I had never thought about how this related to the stability of Earth's climate, but this may be an important consideration for habitability. This also depends on how many other planets are in the solar system, however, and how the other planets influence the rotation of the exoplanet of interest. Nonetheless, this is an intersting thought. Learning more about our moon both helps us learn more about Earth itself, but also about the importance of moons in general. Now the question is: And are the presence of moons any indication of increased habitability on exoplanets?

The Arecibo Message and the search for extraterrestrial life

In 1974, mankind put forth its first attempt at communication with extraterrestrial intelligence (CETI). The effort consisted of a message beamed toward the star cluster M13 by the Arecibo radio telescope. This star cluster is the most prominent globular cluster in the northern half of the sky, and happens to lie in the constellation, Hercules. It spans well over 150 light-years, although the bulk of its over one million stars are concentrated into a core region with a diameter of about 100 light-years.

The Arecibo message consists of a string of 1679 binary digits that can be arranged into 73 rows and 23 columns (prime number multiples of 1679) to represent a picture describing human life on Earth. The uppermost portion of the message establishes that the number system on Earth is binary through a display of dots in formations one through ten, reading right to left. Beneath this appears the atomic numbers for the main biological elements: carbon, hydrogen, oxygen, nitrogen, and phosphorous, beneath which is a model of the chemical structure of DNA. The remaining portion of the message addresses the appearance, size, and number of human beings, as well as our location within our solar system.

Realistically, over the course of its 25,000-year-long journey, its likely that the Arecibo Message will be degraded beyond recognition by its interaction with cosmic dust and particles in the interstellar medium. With the loss of even a few bits of information, the signal will most likely be rendered undecipherable, however, a much larger duplicate message was sent on the 2001 Encounter Mission to address this problem.

The search for extraterrestrial life (SETI) initially began with microwave observation, and has just recently been expanded to include an optical search for extraterrestrial laser pulses. The basic strategy first involves the search for an indicator – a focused radio beam, a brilliant pinpoint of light – that is identifiable as intelligently controlled rather than a purely natural phenomenon (pulsars or quasars) or a human artifact (unexpected transmission from a “lost” satellite). However, the conformation that so many SETI scientists base their career upon could occur today, tomorrow, or never. A thorough search really depends on the exact magnitude of space, the number of technologically advanced civilizations that coincide with ours, as well as the search rate.

In searching for extraterrestrial life, some researchers probe galaxies beyond ours; however, most searches are limited to subsets of the billions of stars within our own galaxy. Additionally, of the searches that are performed, researchers either use an “all sky survey” mentality, which involves an encompassing but superficial look at unselected stars or a “targeted” search which is based on a closer inspections of the five to ten percent of stars that are believed to be promising hosts for life-bearing planets. With the advent of newer, more advanced, technologies, the search for extraterrestrial life by astronomers is looking more and more promising.

What I find to be a particularly interesting aspect of SETI today are the often-overlooked cultural, intellectual, and emotional factors that shape the search as well as the mindsets of the searchers. These factors bring an anthropological, psychological, sociological, as well as historical aspect to the discovery of extraterrestrial life that could help outline interstellar communications that can be understood in cultures that are radically different from our own. Specifically, anthropology (including archaeology and linguistics) along with psychology and cognitive science could be used to decrypt and interpret any message that we may intercept. Then, social psychologists and communications specialists could be used to facilitate the orderly dissemination of news to the public. The understanding of the media and mass communications, organizational functioning, social and psychological influences on attitude formation and change, as well as rumor control can make a huge difference when presenting information to the public. The way in which the information is presented to the public plays a huge role in their response, thus an understanding of human reactions is imperative when it comes to SETI discoveries. It seems like this would be an incredibly difficult task for these specialists appeal to the interests, knowledge, and beliefs of not just one or two nations or regions, but rather the entire human race though. The way that our cultures and societies have diverged in our time on Earth has made it incredibly difficult for these specialists to make this information culturally relevant and available to everyone – as all humans deserve to know if we are not alone in our universe.

Friday, October 29, 2010

Climate Change and Habitability continued

As a branching off point from my previous blog, another interesting comment I came across in the "Hot Zone" blog (about Climate Change) on the astrobiology magazine website was the following: Peter Ward, author of The Medea Hypothesis (2009), has taken the viewpoint (among other scientists) that life is rare in the universe because it is fundamentally harmful in its destabilizing affect on a planet’s climate. This statement is hard to refute in today's world as man's impact of Earth is becoming more and more obvious. I had never heard this theory before, but it is incredibly interesting. What is it about life that is so destabilizing?

This theory seems to go against a prevailing sentiment in society that the workings of the natural world have reached a dynamic equilibrium that is incredibly elegant and durable. Indeed, the notion of biomimetics in which nature is used as a template for man's engineering is based on this sentiment, as are the environmental laws that try to minimize the damaging influence of humans on land and the atmosphere.
This sentiment shows up in Henry David Thoreau's dictum, "In wildness is the preservation of the world." How could we have been so wrong, according to Peter Ward?

Peter Ward, a paleontologist at the University of Washington who specializes in mass extinctions, attacks no prevailing theory as strongly as he does the Gaia Hypothesis: the idea introduced in the 1970s that describes every living thing on Earth as part of one gigantic self-regulating organism. Indeed, in opposition to this hypothesis, Ward named his own hypothesis the Medea Hypothesis (for the Greek sorceress who killed her own children).

First off, what are some of Ward's reasons for this new conception of nature's role on Earth? In his view, the earth's history makes clear that, left to run its course, life is poisonous. He claims that long before humans came onto the scene, primitive life forms were trashing the planet. For example, around 3.7 billion years ago, they created a planet-girdling methane smog that threatened to extinguish every living thing; a little over a billion years later they pumped the atmosphere full of poison gas. (That gas, ironically, was oxygen, which later life forms adapted to use as fuel.)

Ward explains how he sees the story of life on earth as a long series of suicide attempts. Four of the five major mass extinctions since the rise of animals were caused by bacteria, and twice, he argues, the planet was transformed into a nearly total ball of ice thanks to the voracious appetites of plants. In other words, "it's not just human beings, with our chemical spills, nuclear arsenals, and tailpipe emissions, who are a menace. The main threat to life is life itself."

A main point Ward derives from his hypothesis is that the planet would not be better off without humans, rather that life would destroy itself anyways. He believes that environmentalism needs to restructure its underlying philosophy and he believes that humans are needed to save the planet from destruction. This is the start of quite a tangent so I won't go down that path, however, this hypothesis does have significant meaning for astrobiology as well.

This is incredibly important to the search for life on other planets. If life is indeed so toxic, life may be much less likely to exist than we have previously thought. Perhaps, it was not the origin of life that was so lucky on Earth, but rather the perpetuation of that life.

To further relate the Medea Hypothesis to climate change and astrobiology, Ward claims that the evidence of past extinctions - written in fossils and in the chemical makeup of deeply buried rock sediments - as well as the workings of today's oceans, atmosphere, and myriad food chains, shows that Earth tends not toward harmony but towards extremes. Stability appears to occur simply as respites between catastrophic boom-and-bust cycles. He attributes one of the largest extinctions in history to the out-of-control proliferation of plankton feeding on upwellings of nutrients from the ocean floor. Rather than being brought back to equilibrium, the tiny organisms reproduced until they choked off much of the life in the upper ocean. Exhausting their newfound food supply, they died en masse, and decaying by the trillions used up all the oxygen in the water, killing off everything else.

As for the earth's temperature control, more often than not positive feedback loops appear to be common--with warming triggering more warming, and cooling more cooling. In a process we're seeing today, as the planetary temperature rises, warming increases the rate at which soil releases greenhouse gases - not only carbon dioxide, but methane and nitrous oxide. It leads to more forest growth in places that formerly were barren tundra, even as more carbon dioxide in the air makes plants hardier and better able to grow in areas once given over to desert. More plants in more places means a darker earth, and therefore a more heat-absorbent and warmer one. It's an escalating feedback loop that becomes even more powerful as the planet's white, ice-covered poles give way to darker open water.

What does this mean for the search for planets with stable atmopsheres and temperature gradients? Ward's theory does not suggest that we should look for life on planets without stable atmospheres; it does suggest, however, that the origin of life may be relatively common, but that the existence of life may not be. Changes in climate may be driven by life on longer time scales than we are able to observe on other planets. Rather, we still need to look for relative stability to find life, because Ward supposes that life causes instability and thus ultimately condemns itself for extinction. Thus, though climate instability may be an consequence of life, it is not a criteria associated with habitability--it is quite the opposite.

It is also very important to realize that Ward's hypothesis, though incredibly provocative, is not as straight forward as he makes it seem. Though he emphasizes the occurance of positive feedback loops, there are plenty examples of negative feedback loops like those exemplified in the Gaia hypothesis. Indeed, these may still be more common; it may just be that since they are not as prone to catastrophism they are less obvious to observe.

READ THIS: A Debate about the searching for different life forms

Read this article if you have time, it is interesting to think about and tie together some of the things we have been discussing:

"...Let's say we go to Titan, and we find life that has had a separate creation, with no communication with Earth-like life ever. That's not just a separate phylum, kingdom, domain, or dominion, it's a separate tree. As taxonomists, we have to be ready to build a bigger house. Because it's coming -- either we'll find it or we're going to build it, but there will be life as we don't know it in a diversity of form on this planet in this next century. It's being built in many places right now." (Peter Ward)

Climate change and our understanding of habitability.

I was just checking out the astrobiology magazine website, and noticed that there is an entire blog dedicated t o Climate Change and Global Warming:

I initially thought this surprising because it didn't strike me as obvious that astrobiology and climate change would be related, but upon reading more, I learned that the process of watching climate change on Earth and noticing the effects, helps us to understand how climate and habitability relate. Understanding Earth's own climate is necessary to understanding what makes a planet habitable. Climate change makes us appreciate how influential climate is on habitability which is especially vital for the field of astrobiology because of the need to determine the importance of various habitability factors.

It is true that the knowledge gleaned from the study of climate change is most applicable to 'our' life form. Discovering the tipping points that govern whether a temperature is habitable for certain species is incredibly important for determining the habitability of our own planet for our life form, but how can this be extrapolated to other life forms? For one thing, all life will be dependent on climate and it is essentially impossible to imagine life will be adaptable to highly variable climates. Thus a stable climate over time may be crucial. The effects of climate change will be interesting to assess in our life time because of the short time frame in which climate is changing.

One notable thing that climate change has taught us is an appreciation for the interconnectedness of Earth. Timothy Herbert, of Brown University (!) recently wrote a paper on this and highlighted this interconnectedness: “What surprised us is that the tropics seemed to shiver when the polar latitudes get cold, and they warm up when the ice ages pass.” He suggests that the link between the oceans has to do with CO2 levels. The polar oceans absorb a lot of it and can draw down atmospheric levels by as much as 30 percent. This impacts the tropical oceans, which have a powerful influence over global climate conditions. Warm tropical oceans produce water vapor, which drives global rainfall patterns and is a potent greenhouse gas warmer.

Climate change also enhances the importance of relatively stable climate niches for the evolution of life. Such niches like deep sea vents, glaciers, and sub-surface environments are crucially removed from the fluctuating climate. This may be crucial for the ability of life to possibily originate in these niches, and to perhaps remain most primitive because of low levels of selection. Understanding where these niches are located and what makes them stable for life to evolve relatively un-disturbed may shed light on what features to look for in exoplanets to find life.

What are some other ways that climate change can help inform astrobiologists?

Tuesday, October 26, 2010

Nanobacteria: A Different Type of Life???

Nanobacteria (singular nanobacterium) is the name of a proposed class of living organisms, specifically cell-walled microorganisms with a size much smaller than the generally accepted lower limit size for life (about 200 nanometres for bacteria). The status of nanobacteria is controversial, with some researchers suggesting they are a new class of living organisms capable of incorporating radiolabeled uridine and others attributing to them a simpler, abiotic nature.

The term 'calcifying nanoparticles' (CNPs) has also been used as a conservative name regarding their possible status as a life form. The most recent research tends to agree that these structures exist, and probably replicate in some way. Their status as living entities is still hotly debated, though some researchers now claim that the case that they are nonliving crystalline particles is conclusively proven.

They were first described in 1981 by Torella and Morita and were discovered because of their implication in the formation of both kidney stones and arterial plaque. Early in 1989, geologist Robert L. Folk found what he later identified as nannobacteria (written with double "n"), that is, nanoparticles isolated from geological specimen in travertine from hot springs of Viterbo, Italy. He proposed that nanobacteria are the principal agents of precipitation of all minerals and crystals on Earth formed in liquid water, that they also cause all oxidation of metals, and that they are abundant in many biological specimens. In 1996, NASA scientist David McKay published a study suggesting the existence of nanofossils — fossils of Martian nanobacteria — in ALH84001, a meteorite originating from Mars and found in Antarctica.

According to the Finnish researcher Olavi Kajander and Turkish researcher Neva Ciftcioglu, the particles self-replicated in microbiological culture, and the researchers further reported having identified DNA in these structures by staining.

A paper published in 2000 led by John Cisar further tested these ideas and claimed that what had previously been described as "self-replication" was a form of crystalline growth. The only DNA detected in his specimens was identified as coming from the bacteria Phyllobacterium mysinacearum, which is a common contaminant in PCR reactions. An article in PLoS in 2008 focused on the comprehensive characterization of nanobacteria. The authors say that their results rule out the existence of nanobacteria as living entities, instead revealing that they are a unique self-propagating entity and that they are self-propagating mineral-fetuin complexes. Another 2008 PNAS article reported that blood nanobacteria are not living organisms and stated that "CaCO3 precipitates prepared in vitro are remarkably similar to purported nanobacteria in terms of their uniformly sized, membrane-delineated vesicular shapes, with cellular division-like formations and aggregations in the form of colonies."

The growth of such "biomorphic" inorganic precipitates was studied in detail in a 2009 Science paper, which showed that unusual crystal growth mechanisms can produce witherite precipitates from barium chloride and silica solutions that closely resemble primitive organisms. The authors commented on the close resemblance of these crystals to putative nanobacteria, stating that their results showed that evidence for life cannot rest on morphology alone.

This once again relates back to the definition of life and how we determine if something is alive if we are dealing with an alien life form. Another example is that of viruses, in which some scientists, like the paleontologist Peter Ward, classify as living. He says that our current tree of life leaves no room for viruses which he suggests are living things, and will likely be an entirely useless concept for classfying alien life. Indeed, some evolutionary biologists today believe the current phylogenetic tree to be incapable of classifying life in an accurate way because it is a human construct that is organized not necessarily according to classifications defined by nature itself, but by ease of convenience for human understanding. Thus the search for alien life needs a restructuring of how we think about life itself.

Monday, October 25, 2010

Exoplanet Atmospheric Studies

Look at the Exoplanet timeline:

To astronomers, a "potentially habitable" planet is one that could sustain life. Habitability depends on many factors, but having liquid water and an atmosphere are among the most important. Thus determining the characteristics of the atmospheres of exoplanets and the possible implications of these characteristics on habitability are key areas of research in astrobiology.
A history of the detection of exoplanet atmospheres is brief because the technology that it takes to do this work has been recently invented and applied. Visible-light telescopes can detect exoplanets and determine certain characteristics, such as their sizes and orbits, but not much can be inferred about their atmospheres or what they look like. Therefore, exoplanet atmospheric studies was largely pioneered in 2005 by Spitzer, when it became the first telescope to directly detect photons from an exoplanet by examining their infrared light and using spectrometry to detect the molecules present in the exoplanet atmospheres by their unique ‘spectral fingerprint.’ Since then, Spitzer, along with NASA's Hubble Space Telescope, has studied the atmospheres of several hot Jupiters (very hot, giant gas planets that orbit very closely to their star), finding water, methane, carbon dioxide and carbon monoxide. The first near-infrared emission spectrum obtained for an exoplanet was that of HD 189733b.
The Hubble telescope was conceived primarily for observations of the distant universe, yet it is also important for exoplanet atmospheric studies because we can use Hubble's near infrared camera and multi-object spectrometer to study infrared light emitted from planets. Gases in the planet's atmosphere absorb certain wavelengths of light from the planet's hot glowing interior and the molecules leave a unique spectral fingerprint on the radiation from the planet that reaches Earth. This observation is best done on planets with orbits tilted edge-on to Earth because of the usefulness of eclipses. The eclipses allow an opportunity to subtract the light of the star alone, when the planet is blocked, from that of the star and planet together prior to eclipse. That isolates the emission of the planet and makes possible a chemical analysis of its atmosphere. Searching for molecules in exoplanet atmospheres is important because molecules present are expected to: (1) influence strongly the balance of atmospheric radiation, (2) trace dynamical and chemical processes and (3) indicate the presence of disequilibrium effects. Thus searching for molecules is a high priority because they have to potential to
reveal atmospheric conditions and chemistry which will help us infer the habitability of the planet.

05.09.07, “NASA Finds Extremely Hot Planet, Makes First Exoplanet Weather Map.”
On this date, researchers using NASA's Spitzer Space Telescope learned what the weather is like on two distant, exotic worlds—giant gas planets: HD 189733b and HD 149026b. They mapped the weather patterns on HD 189733b by using the Spitzer telescope to measure the infrared light coming from the planet as it circled around its star and from this, they created a map of the temperature of the entire surface of the planet based from a quarter of a million data points. They found that the planet is likely whipped by roaring winds and that temperatures are fairly even considering the planet is tidally locked: 650 degrees C (1,200 F) on the dark side to 930 degrees C (1,700 F) on the sunlit side. It is assumed that many hot Jupiters are tidally locked so it is interesting that the planet's overall temperature variation is mild and at the time, scientists believed winds must be spreading the heat from its permanently sunlit side around to its dark side. Such winds occur at up to 9600 kph (6,000 mph); in comparison, jet streams on Earth travel at 322 kph(200 mph). This is interesting because now we are beginning to see how these hot Jupiters deal with the incredible amount of energy blasted at them—20,000 times more energy per second than Jupiter. Also of interest, HD 189733b has a warm spot 30 degrees east of ‘high noon.’ Assuming the planet is tidally locked to its parent star, the researchers at the time suggested that this implies that fierce winds are blowing eastward.
The main interesting finding regarding HD 149026b was that it was the hottest planet found to date at a scorching 2,038 degrees C (3,700 F), which is even hotter than some low-mass stars. This suggests that the heat is not being spread around in contrast to HD 189733b. HD 149026b is the smallest and densest known transiting planet, with a size similar to Saturn's and a core suspected to be 70 to 90 times the mass of Earth. It also probably reflects almost no starlight, instead absorbing all of the heat which means HD 149026b might be the blackest planet known, in addition to the hottest.

The near-infrared transmission spectrum of the planet HD 189733b, described above, shows the presence of methane and water vapor. This is the first time that water was found to exist in the atmosphere of an exoplanet. The discovery of methane was interesting because, on thermochemical grounds, carbon monoxide is expected to be abundant in the upper atmosphere of hot-Jupiter planets like HD 189733b. The detection of methane rather than carbon monoxide in such a hot planet could signal the presence of a horizontal chemical gradient away from the permanent dayside, or it may imply an ill-understood photochemical mechanism that leads to an enhancement of methane. The Hubble Space Telescope also discovered carbon dioxide in the atmosphere. This marked an important step toward finding chemical biotracers of extraterrestrial life even though in this instance, HD 189733b is way too hot for life to be feasible. But because organic compounds can be a by-product of life processes, their detection on an Earth-like planet someday may provide the first evidence of life beyond our planet.
In contrast to the larger than expected amount of methane found on HD 189733b, GJ 436b has very little methane. This is peculiar because models of planetary atmospheres indicate that any world with the common mix of hydrogen, carbon and oxygen, and a temperature up to 1,000 K (1,340 degrees F)—cooler than HD 189733b—should have a large amount of methane and a small amount of carbon monoxide. However, at about 800 Kelvin (or 980 F), GJ 436b does not. This again demonstrates the lack of scientific understanding of atmospheres of exoplanets and also the diversity of exoplanets that exist.

There have been various models created to better understand the possible atmospheric characteristics of different exoplanets. One type of planet that has been modeled is that of planets occurring in the habitable zone of red dwarfs. Planets within the habitable zones of M dwarfs are likely to be synchronous rotators (tidally locked with a fixed light and dark side). Scientists have made three-dimensional simulations of the atmospheres of such planets and determine that near the ground, a thermally direct longitudinal cell exists, transporting heat from the dayside to the nightside. The circulation is three-dimensional, with low-level winds returning mass to the dayside across the polar regions and higher up, the zonally averaged winds display a pattern of strong super-rotation due to these planets' finite (albeit small) rotation rate. The main claim is that planets orbiting M stars can support atmospheres over a large range of conditions and, despite constraints such as stellar activity, are very likely to be habitable.

Simulations of atmospheres of Earth-like aquaplanets that are tidally locked to their star have also been created and described. These models illustrate how planetary rotation and insolation distribution shape climate. In these models, the winds are ‘approximately isotropic and divergent at leading order in the slowly rotating atmosphere but are predominantly zonal and rotational in the rapidly rotating atmosphere.’ Furthermore, ‘free-atmospheric horizontal temperature variations in the slowly rotating atmosphere are generally weaker than in the rapidly rotating atmosphere.’ A curious result is that the surface temperature on the night side of the planets does not fall below ∼240 K in either the rapidly or slowly rotating atmosphere which means that heat transport from the day side to the night side of the planets efficiently reduces temperature contrasts in either case. This creates a relatively mild temperature difference across even a tidally locked aquaplanet. Also described is the distribution of winds, temperature, and precipitation, with rotational waves and eddies of primary influence in the rapidly rotating atmosphere and simpler divergent circulations influential in the slowly rotating atmosphere. Both the slowly and rapidly rotating atmospheres exhibit equatorial superrotation which varies non-monotonically with rotation rate, however, the surface temperature contrast between the day side and the night side does not vary strongly with changes in rotation rate.

In the near future, astronomers look forward to using the James Webb Space Telescope (to be hopefully completed around 2014) to look spectroscopically for biomarkers on a terrestrial planet near the size of Earth. The Webb telescope should be able to make much more sensitive measurements of these primary and secondary eclipse events than the technology currently available which will hopefully bring us a much greater ability to detect and characterize exoplanet atmospheres.