A New Physics Theory of Life

Natalie Wolchover, 01/22/14

Why does life exist?

Popular hypotheses credit a primordial soup, a bolt of lightning and a colossal stroke of luck. But if a provocative new theory is correct, luck may have little to do with it. Instead, according to the physicist proposing the idea, the origin and subsequent evolution of life follow from the fundamental laws of nature and “should be as unsurprising as rocks rolling downhill.”

From the standpoint of physics, there is one essential difference between living things and inanimate clumps of carbon atoms: The former tend to be much better at capturing energy from their environment and dissipating that energy as heat. Jeremy England, a 31-year-old assistant professor at the Massachusetts Institute of Technology, has derived a mathematical formula that he believes explains this capacity. The formula, based on established physics, indicates that when a group of atoms is driven by an external source of energy (like the sun or chemical fuel) and surrounded by a heat bath (like the ocean or atmosphere), it will often gradually restructure itself in order to dissipate increasingly more energy. This could mean that under certain conditions, matter inexorably acquires the key physical attribute associated with life.

“You start with a random clump of atoms, and if you shine light on it for long enough, it should not be so surprising that you get a plant,” England said.

England’s theory is meant to underlie, rather than replace, Darwin’s theory of evolution by natural selection, which provides a powerful description of life at the level of genes and populations. “I am certainly not saying that Darwinian ideas are wrong,” he explained. “On the contrary, I am just saying that from the perspective of the physics, you might call Darwinian evolution a special case of a more general phenomenon.”

His idea, detailed in a recent paper and further elaborated in a talk he is delivering at universities around the world, has sparked controversy among his colleagues, who see it as either tenuous or a potential breakthrough, or both.

England has taken “a very brave and very important step,” said Alexander Grosberg, a professor of physics at New York University who has followed England’s work since its early stages. The “big hope” is that he has identified the underlying physical principle driving the origin and evolution of life, Grosberg said.

“Jeremy is just about the brightest young scientist I ever came across,” said Attila Szabo, a biophysicist in the Laboratory of Chemical Physics at the National Institutes of Health who corresponded with England about his theory after meeting him at a conference. “I was struck by the originality of the ideas.”

Others, such as Eugene Shakhnovich, a professor of chemistry, chemical biology and biophysics at Harvard University, are not convinced. “Jeremy’s ideas are interesting and potentially promising, but at this point are extremely speculative, especially as applied to life phenomena,” Shakhnovich said.

England’s theoretical results are generally considered valid. It is his interpretation — that his formula represents the driving force behind a class of phenomena in nature that includes life — that remains unproven. But already, there are ideas about how to test that interpretation in the lab.

“He’s trying something radically different,” said Mara Prentiss, a professor of physics at Harvard who is contemplating such an experiment after learning about England’s work. “As an organizing lens, I think he has a fabulous idea. Right or wrong, it’s going to be very much worth the investigation.”

At the heart of England’s idea is the second law of thermodynamics, also known as the law of increasing entropy or the “arrow of time.” Hot things cool down, gas diffuses through air, eggs scramble but never spontaneously unscramble; in short, energy tends to disperse or spread out as time progresses. Entropy is a measure of this tendency, quantifying how dispersed the energy is among the particles in a system, and how diffuse those particles are throughout space. It increases as a simple matter of probability: There are more ways for energy to be spread out than for it to be concentrated. Thus, as particles in a system move around and interact, they will, through sheer chance, tend to adopt configurations in which the energy is spread out. Eventually, the system arrives at a state of maximum entropy called “thermodynamic equilibrium,” in which energy is uniformly distributed. A cup of coffee and the room it sits in become the same temperature, for example. As long as the cup and the room are left alone, this process is irreversible. The coffee never spontaneously heats up again because the odds are overwhelmingly stacked against so much of the room’s energy randomly concentrating in its atoms.

Although entropy must increase over time in an isolated or “closed” system, an “open” system can keep its entropy low — that is, divide energy unevenly among its atoms — by greatly increasing the entropy of its surroundings. In his influential 1944 monograph “What Is Life?” the eminent quantum physicist Erwin Schrödinger argued that this is what living things must do. A plant, for example, absorbs extremely energetic sunlight, uses it to build sugars, and ejects infrared light, a much less concentrated form of energy. The overall entropy of the universe increases during photosynthesis as the sunlight dissipates, even as the plant prevents itself from decaying by maintaining an orderly internal structure.

Life does not violate the second law of thermodynamics, but until recently, physicists were unable to use thermodynamics to explain why it should arise in the first place. In Schrödinger’s day, they could solve the equations of thermodynamics only for closed systems in equilibrium. In the 1960s, the Belgian physicist Ilya Prigogine made progress on predicting the behavior of open systems weakly driven by external energy sources (for which he won the 1977 Nobel Prize in chemistry). But the behavior of systems that are far from equilibrium, which are connected to the outside environment and strongly driven by external sources of energy, could not be predicted.

This situation changed in the late 1990s, due primarily to the work of Chris Jarzynski, now at the University of Maryland, and Gavin Crooks, now at Lawrence Berkeley National Laboratory. Jarzynski and Crooks showed that the entropy produced by a thermodynamic process, such as the cooling of a cup of coffee, corresponds to a simple ratio: the probability that the atoms will undergo that process divided by their probability of undergoing the reverse process (that is, spontaneously interacting in such a way that the coffee warms up). As entropy production increases, so does this ratio: A system’s behavior becomes more and more “irreversible.” The simple yet rigorous formula could in principle be applied to any thermodynamic process, no matter how fast or far from equilibrium. “Our understanding of far-from-equilibrium statistical mechanics greatly improved,” Grosberg said. England, who is trained in both biochemistry and physics, started his own lab at MIT two years ago and decided to apply the new knowledge of statistical physics to biology.

Using Jarzynski and Crooks’ formulation, he derived a generalization of the second law of thermodynamics that holds for systems of particles with certain characteristics: The systems are strongly driven by an external energy source such as an electromagnetic wave, and they can dump heat into a surrounding bath. This class of systems includes all living things. England then determined how such systems tend to evolve over time as they increase their irreversibility. “We can show very simply from the formula that the more likely evolutionary outcomes are going to be the ones that absorbed and dissipated more energy from the environment’s external drives on the way to getting there,” he said. The finding makes intuitive sense: Particles tend to dissipate more energy when they resonate with a driving force, or move in the direction it is pushing them, and they are more likely to move in that direction than any other at any given moment.

“This means clumps of atoms surrounded by a bath at some temperature, like the atmosphere or the ocean, should tend over time to arrange themselves to resonate better and better with the sources of mechanical, electromagnetic or chemical work in their environments,” England explained.

Self-replication (or reproduction, in biological terms), the process that drives the evolution of life on Earth, is one such mechanism by which a system might dissipate an increasing amount of energy over time. As England put it, “A great way of dissipating more is to make more copies of yourself.” In a September paper in the Journal of Chemical Physics, he reported the theoretical minimum amount of dissipation that can occur during the self-replication of RNA molecules and bacterial cells, and showed that it is very close to the actual amounts these systems dissipate when replicating. He also showed that RNA, the nucleic acid that many scientists believe served as the precursor to DNA-based life, is a particularly cheap building material. Once RNA arose, he argues, its “Darwinian takeover” was perhaps not surprising.

The chemistry of the primordial soup, random mutations, geography, catastrophic events and countless other factors have contributed to the fine details of Earth’s diverse flora and fauna. But according to England’s theory, the underlying principle driving the whole process is dissipation-driven adaptation of matter.

This principle would apply to inanimate matter as well. “It is very tempting to speculate about what phenomena in nature we can now fit under this big tent of dissipation-driven adaptive organization,” England said. “Many examples could just be right under our nose, but because we haven’t been looking for them we haven’t noticed them.”

Scientists have already observed self-replication in nonliving systems. According to new research led by Philip Marcus of the University of California, Berkeley, and reported in Physical Review Letters in August, vortices in turbulent fluids spontaneously replicate themselves by drawing energy from shear in the surrounding fluid. And in a paper appearing online this week in Proceedings of the National Academy of Sciences, Michael Brenner, a professor of applied mathematics and physics at Harvard, and his collaborators present theoretical models and simulations of microstructures that self-replicate. These clusters of specially coated microspheres dissipate energy by roping nearby spheres into forming identical clusters. “This connects very much to what Jeremy is saying,” Brenner said.

Besides self-replication, greater structural organization is another means by which strongly driven systems ramp up their ability to dissipate energy. A plant, for example, is much better at capturing and routing solar energy through itself than an unstructured heap of carbon atoms. Thus, England argues that under certain conditions, matter will spontaneously self-organize. This tendency could account for the internal order of living things and of many inanimate structures as well. “Snowflakes, sand dunes and turbulent vortices all have in common that they are strikingly patterned structures that emerge in many-particle systems driven by some dissipative process,” he said. Condensation, wind and viscous drag are the relevant processes in these particular cases.

“He is making me think that the distinction between living and nonliving matter is not sharp,” said Carl Franck, a biological physicist at Cornell University, in an email. “I’m particularly impressed by this notion when one considers systems as small as chemical circuits involving a few biomolecules.”

England’s bold idea will likely face close scrutiny in the coming years. He is currently running computer simulations to test his theory that systems of particles adapt their structures to become better at dissipating energy. The next step will be to run experiments on living systems.

Prentiss, who runs an experimental biophysics lab at Harvard, says England’s theory could be tested by comparing cells with different mutations and looking for a correlation between the amount of energy the cells dissipate and their replication rates. “One has to be careful because any mutation might do many things,” she said. “But if one kept doing many of these experiments on different systems and if [dissipation and replication success] are indeed correlated, that would suggest this is the correct organizing principle.”

Brenner said he hopes to connect England’s theory to his own microsphere constructions and determine whether the theory correctly predicts which self-replication and self-assembly processes can occur — “a fundamental question in science,” he said.

Having an overarching principle of life and evolution would give researchers a broader perspective on the emergence of structure and function in living things, many of the researchers said. “Natural selection doesn’t explain certain characteristics,” said Ard Louis, a biophysicist at Oxford University, in an email. These characteristics include a heritable change to gene expression called methylation, increases in complexity in the absence of natural selection, and certain molecular changes Louis has recently studied.

If England’s approach stands up to more testing, it could further liberate biologists from seeking a Darwinian explanation for every adaptation and allow them to think more generally in terms of dissipation-driven organization. They might find, for example, that “the reason that an organism shows characteristic X rather than Y may not be because X is more fit than Y, but because physical constraints make it easier for X to evolve than for Y to evolve,” Louis said.

“People often get stuck in thinking about individual problems,” Prentiss said.  Whether or not England’s ideas turn out to be exactly right, she said, “thinking more broadly is where many scientific breakthroughs are made.”

Emily Singer contributed reporting. This article was reprinted on ScientificAmerican.com.

https://www.simonsfoundation.org/quanta/20140122-a-new-physics-theory-of-life/

Chemists Show Life on Earth Not a Fluke            

Andrew Bissette, 10/24/13

How life came about from inanimate sets of chemicals is still a mystery. While we may never be certain which chemicals existed on prebiotic Earth, we can study the biomolecules we have today to give us clues about what happened three billion years ago.

Now scientists have used a set of these biomolecules to show one way in which life might have started. They found that these molecular machines, which exist in living cells today, don’t do much on their own. But as soon as they add fatty chemicals, which form a primitive version of a cell membrane, it got the chemicals close enough to react in a highly specific manner.

This form of self-organisation is remarkable, and figuring out how it happens may hold the key to understanding life on earth formed and perhaps how it might form on other planets.

The 1987 Nobel Prize in Chemistry was given to chemists for showing how complex molecules can perform very precise functions. One of the behaviours of these molecules is called self-organisation, where different chemicals come together because of the many forces acting on them and become a molecular machine capable of even more complex tasks. Each living cell is full of these molecular machines.

Pasquale Stano at the University of Roma Tre and his colleagues were interested in using this knowledge to probe the origins of life. To make things simple, they chose an assembly that produces proteins. This assembly consists of 83 different molecules including DNA, which was programmed to produce a special green fluorescent protein (GFP) that could be observed under a confocal microscope.

The assembly can only produce proteins when its molecules are close enough together to react with each other. When the assembly is diluted with water, they can no longer react. This is one reason that the insides of living cells are very crowded, concentrated places: to allow the chemistry of life to work.

In order to recreate this molecular crowding, Stano added a chemical called POPC to the dilute solution. Fatty molecules such as POPC do not mix with water, and when placed into water they automatically form liposomes. These have a very similar structure to the membranes of living cells and are widely used to study the evolution of cells.

Stano reports in the journal Angewandte Chemie that many of these liposomes trapped some molecules of the assembly. But remarkably, five in every 1,000 such liposomes had all 83 of the molecules needed to produce a protein. These liposomes produced large amount of GFP and glowed green under a microscope.

Computer calculations reveal that even by chance, five liposomes in 1,000 could not have trapped all 83 molecules of the assembly. Their calculated probability for even one such liposome to form is essentially zero. The fact that any such liposomes formed and that GFP was produced means something quite unique is happening.

Stano and his colleagues do not yet understand why this happened. It may yet be a random process that a better statistical model will explain. It may be that these particular molecules are suited to this kind of self-organisation because they are already highly evolved. An important next step is to see if similar, but less complex, molecules are also capable of this feat.

Regardless of the limitations, Stano’s experiment has shown for the first time that self-assembly of molecular machines into simple cells may be an inevitable physical process. Finding out how exactly this self-assembly happens will mean taking a big step towards understanding how life was formed.

Andrew Bissette is a PhD student at University of Oxford

http://www.realclearscience.com/articles/2013/10/24/chemists_show_life_on_earth_not_a_fluke_106733.html

7 Theories on the Origin of Life

Charles Q. Choi, LiveScience Contributor, 03/22/11

Primordial soup

Life on Earth began more than 3 billion years ago, evolving from the most basic of microbes into a dazzling array of complexity over time. But how did the first organisms on the only known home to life in the universe develop from the primordial soup?

Here are science's theories on the origins of life on Earth.

Electric Spark

Electric sparks can generate amino acids and sugars from an atmosphere loaded with water, methane, ammonia and hydrogen, as was shown in the famous Miller-Urey experiment reported in 1953, suggesting that lightning might have helped create the key building blocks of life on Earth in its early days. Over millions of years, larger and more complex molecules could form. Although research since then has revealed the early atmosphere of Earth was actually hydrogen-poor, scientists have suggested that volcanic clouds in the early atmosphere might have held methane, ammonia and hydrogen and been filled with lightning as well.

Community Clay

The first molecules of life might have met on clay, according to an idea elaborated by organic chemist Alexander Graham Cairns-Smith at the University of Glasgow in Scotland. These surfaces might not only have concentrated these organic compounds together, but also helped organize them into patterns much like our genes do now.

The main role of DNA is to store information on how other molecules should be arranged. Genetic sequences in DNA are essentially instructions on how amino acids should be arranged in proteins. Cairns-Smith suggests that mineral crystals in clay could have arranged organic molecules into organized patterns. After a while, organic molecules took over this job and organized themselves.

Deep-Sea Vents

The deep-sea vent theory suggests that life may have begun at submarine hydrothermal vents, spewing key hydrogen-rich molecules. Their rocky nooks could then have concentrated these molecules together and provided mineral catalysts for critical reactions. Even now, these vents, rich in chemical and thermal energy, sustain vibrant ecosystems.

Chilly Start

Ice might have covered the oceans 3 billion years ago, as the sun was about a third less luminous than it is now. This layer of ice, possibly hundreds of feet thick, might have protected fragile organic compounds in the water below from ultraviolet light and destruction from cosmic impacts. The cold might have also helped these molecules to survive longer, allowing key reactions to happen.

RNA World

Nowadays DNA needs proteins in order to form, and proteins require DNA to form, so how could these have formed without each other? The answer may be RNA, which can store information like DNA, serve as an enzyme like proteins, and help create both DNA and proteins. Later DNA and proteins succeeded this "RNA world," because they are more efficient. RNA still exists and performs several functions in organisms, including acting as an on-off switch for some genes. The question still remains how RNA got here in the first place. And while some scientists think the molecule could have spontaneously arisen on Earth, others say that was very unlikely to have happened. 

Other nucleic acids other than RNA have been suggested as well, such as the more esoteric PNA or TNA.

Simple Beginnings

Instead of developing from complex molecules such as RNA, life might have begun with smaller molecules interacting with each other in cycles of reactions. These might have been contained in simple capsules akin to cell membranes, and over time more complex molecules that performed these reactions better than the smaller ones could have evolved, scenarios dubbed "metabolism-first" models, as opposed to the "gene-first" model of the "RNA world" hypothesis.

Panspermia

Perhaps life did not begin on Earth at all, but was brought here from elsewhere in space, a notion known as panspermia. For instance, rocks regularly get blasted off Mars by cosmic impacts, and a number of Martian meteorites have been found on Earth that some researchers have controversially suggested brought microbes over here, potentially making us all Martians originally. Other scientists have even suggested that life might have hitchhiked on comets from other star systems. However, even if this concept were true, the question of how life began on Earth would then only change to how life began elsewhere in space.

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http://www.livescience.com/13363-7-theories-origin-life.html

Cosmic Cookers: Asteroids May Have Nurtured Seeds of Life

Stephanie Pappas, LiveScience Senior Writer

The chemical building blocks that make life possible on Earth may have aged to perfection in asteroids, according to a new study.

The research, an analysis of a meteorite that fell on a frozen Canadian lake in 2000, reveals a surprisingly large variation in the organic chemicals found among different chunks of the meteorite. The results suggest the emergence of life on Earth may have depended on a "Goldilocks" situation in asteroids in the few million years after the solar system formed, said study researcher Christopher Herd of the University of Alberta.

"Not too hot, not too cold, just right," Herd told LiveScience. "And not too much water alteration and not too little… If you take that material and deliver it to the early Earth, then you deliver what you need for life." [7 Theories on the Origin of Life]

Other past research has suggested comets were the objects that delivered life's ingredients to Earth. (These giant chunks of ice, along with rocky asteroids, are thought to be leftovers from the formation of our solar system.)

An explosive opportunity

Scientists believe that meteorites landing on early Earth may have seeded the new planet with the chemicals necessary to make life, including sugars and the amino acids that build proteins. These meteorites would likely break off of asteroid parent bodies, and so factors such as temperature and water levels in the asteroid could influence the chemicals that are formed within the meteorite. [Read: 5 Reasons to Care About Asteroids]

In 2006, Herd led a successful effort to purchase what is left of a large, 123,000-pound (56 metric tons) meteoroid that exploded over southwestern Canada's Tagish Lake on Jan. 18, 2000. The vast majority of the meteorite evaporated in an enormous explosion in the atmosphere over the lake, but collectors managed to retrieve about 22 pounds (10 kg) of meteorite fragments in the days after the event. The fragments were never touched by hand, and they've never been heated above freezing, preserving the organic compounds inside.

As he was documenting the meteorite haul, Herd noticed that some fragments looked very different from others.

"Some of them looked really dark, and they shed a residue of fine black dust," he said. "Others looked more salt-and-pepper, and they looked more coherent. So I wondered why there was this variation."

He chose four fragments covering the range of appearances for chemical analysis and found that there was more to the differences than met the naked eye. [See a picture of the meteorite]

"What we've shown is that there is a huge variation, a surprisingly large variation, especially in the organic matter that we see just among these four specimens," Herd said.

Most notable, Herd said, were differences in the types of amino acids and monocarboxylic acids among all four specimens (the latter compounds an important component in cell walls, he said).

Seeds of life

Herd and his colleagues suspect that the differences stem from the way water percolated on the meteorite's parent asteroid about 4.6 billion years ago when the solar system was forming. People have theorized about the influence of water on the chemistry of asteroids, he said, but this is the first time anyone has seen these sorts of chemical variations on one meteorite.

"The next step is to go through and see if we've captured the full range of variation, and then go in and do some more sophisticated work" on the compounds found, Herd said.

The findings could shed light on how important interstellar geology may have been to the rise of life on Earth, Herd said.

"It means that what you'd get delivered to the surface of the Earth actually depends on what is going on on the asteroid," he said. 

Herd and his colleagues reported their results today (June 9) in the journal Science.

You can follow LiveScience senior writer Stephanie Pappas on Twitter @sipappas. Follow LiveScience for the latest in science news and discoveries on Twitter @livescience and on Facebook.

• 7 Theories on the Origin of Life 
• Extremophiles: World's Weirdest Life 
• 5 Bold Claims of Alien Life 

http://news.yahoo.com/s/livescience/20110609/sc_livescience/cosmiccookersasteroidsmayhavenurturedseedsoflife

Most Ancient Fossils Aren't Life, Study Suggests

Charles Q. Choi, Astrobiology Magazine

Structures thought of as the oldest known fossils of microbes might actually be microscopic mineral formations not associated with life, suggesting that astrobiologists must be careful calling alien objects "life" when scientists have trouble telling what is or was alive on Earth.

More than 20 years ago, microscopic structures uncovered in the roughly 3.5-billion-year-old Apex Chert formation in western Australia were described as the oldest microbial fossils. These structures were interpreted as cyanobacteria, once known as blue-green algae, embedded in a silica-loaded rock formed in a shallow marine setting. These structures were all detected in slices of rock just 300 microns thick, or roughly three times the diameter of a human hair.

However, the interpretation of the structures has always been controversial, and it is still hotly debated among scientists searching for Earth’s earliest evidence for life. Specimens from the site apparently displayed branching structures that some researchers said were inconsistent with life, while others dismissed such branching as artifacts from photo software

Analysis of the structures themselves suggested they were carbon-based, and therefore associated with the organic chemistry of life, but some contended they were a type of carbon known as graphite, while others said they were kerogen, a mixture of organic compounds. [5 Bold Claims of Alien Life]

Now University of Kansas geospectroscopist Craig Marshall and his colleagues have taken another look at the Apex Chert structures and determined they might not be carbon-based after all. Instead, they seem to just be a series of fractures filled with crystals.

"It's one of those funny moments in science when you go out to do one thing and it completely flips 180 on you," Marshall said.

Earth's oldest fossils

The scientists collected 130 pounds (60 kilograms) of samples from the original site and made very thin slices 30 to 300 microns thick.

"We were interested in developing new methods of looking at ancient microfossils, and so we were drawn to the Apex Chert as these putative microfossils are so iconic," Marshall explained. "However, when we started working on the rocks, we discovered things were a little more complex than we thought they would be."

In the thicker slices, they saw reddish-brown features resembling the previously described microfossils. However, in the thinner slices, these structures appeared to be less like microbes and more like fractures. These cracks seem to be filled with a light mineral possessing a coarse block-like texture, as well as with a dark mineral that came in thin plates. Further analysis suggests the lighter material was quartz and the darker matter was iron-rich hematite.

Marshall and his colleagues note they could be looking at different structures than past studies did, which could explain why the results of their chemical analyses differ. However, Marshall suggested there could also be a number of other explanations — for instance, prior investigations might have mistakenly analyzed carbon-rich material on the surface of the structures and concluded the "microfossils" themselves were carbonaceous. Also, in the analytical methods the researchers used, the signature for hematite is very similar to that of carbon.

"It was a lesson in believing in the data over what is 'known' about these microstructures," Marshall said.

"These results explain the conundrum of the pale color of the microstructures — if they were truly organic, they shouldn't be pale in such metamorphosed rocks," said geobiologist Roger Buick at the University of Washington, who did not take part in this research.  Buick studies the Archean eon, which lasted from 3.8 billion to 2.5 billion years ago and encompasses the time when life first arose on Earth. "Their most important implication is that they virtually seal the case that has been building for many years that these microstructures are not ancient microfossils of cyanobacteria." [7 Theories on the Origin of Life]

"It is still worthwhile searching for Archean microfossils, and specifically for cyanobacterial microfossils, because there are other independent lines of evidence that oxygenic photosynthesis and hence cyanobacteria first evolved during the Archean eon," Buick added. "However, the scarcity of well-preserved rocks of such ancient age will make the task very difficult."

Earth's earliest life

Paleobiologist J. William Schopf at the University of California, Los Angeles, who originally interpreted the Apex Chert structures to be cyanobacteria-like fossils, has noted that he and a colleague have prepared a response to this new study, but it won’t be available for a few weeks.

If the new study is true, the findings are important not only when it comes to evaluating evidence of life in ancient rocks on Earth, but have ramifications for astrobiological prospecting elsewhere in the universe.

"If it is really this hard to find convincing evidence for life on early Earth when we know there is life on Earth now, then it becomes clear that we need to be extra cautious interpreting data collected on Mars," said paleobiogeochemist Alison Olcott Marshall at the University of Kansas, a co-author of the new study.

The scientists detailed their findings online Feb. 20 in the journal Nature Geoscience.

This story was provided to LiveScience by Astrobiology Magazine. 

• 5 Bold Claims of Alien Life 
• Extremophiles: World's Weirdest Life 
• Ancient Fossils, or Just Plain Rocks?

http://news.yahoo.com/s/livescience/20110325/sc_livescience/mostancientfossilsarentlifestudysuggests

Discover雜誌(2010 11月)有一篇文章：

Cosmic Blueprint Of Life 作者：Andrew Grant

對天文化學家就生化物質如何在太空中形成，科學家如何在實驗室複製它們，科學家如何在太空中偵測到它們，以及科學家研究出太空中的生化物質如何落到地球上等等，有詳細報導。對這個主題有興趣的網友請參考。