* Astronomy

When the space shuttle Columbia broke apart during re-entry February 1, 2003, more than 80 on-board science experiments were lost in the fiery descent.

Texas State University-San Marcos biologist Robert McLean, however, has salvaged some unexpected science from the wreckage. A strain of slow-growing bacteria survived the crash, a discovery which may have significant implications for the concept of panspermia. The findings will be published in the May 2006 issue of Icarus, the international journal of solar system studies.

Panspermia is the idea that life--hitchhiking on rocks ejected from meteorite impacts on one world--could travel through space and seed other worlds with life under favourable conditions. Because the conditions under which panspermia could function are so harsh, however, there's been little direct testing of the hypothesis.

"That might have been in the back of my mind when we recovered our payload. My first thinking when we found our payload was, 'Let's look for survivors.'" - Robert McLean.

McLean, along with a team of Texas State researchers, had placed an experiment package aboard the Columbia to investigate the interactions of three different bacterial species in microgravity. When the shuttle broke up over Texas, they assumed the experiment lost--until it turned up, relatively intact, in the parking lot of a Nacogdoches convenience store.
And he found survivors - a bacterium called Microbispora.
Ironically, Microbispora wasn't one of the three species McLean expected to find. The slow-growing organism is normally found in the soil, and McLean determined that it had contaminated the experiment prior to launch. With the Icarus publication, McLean anticipates request for samples of this rugged strain to come in from researchers around the world.

"This organism appears to have survived an atmospheric passage, with the heat and the force of impact. That's only about a fifth of the speed that something on a real meteorite would have to survive, but it is at least five or six times faster than what's been tested before. This is important for panspermia, because if something survives space travel, it eventually has to get down to the Earth and survive passage through the atmosphere and impact. This doesn't prove anything - it just contributes evidence to the plausibility of panspermia. Realistically, that's all it can do. Out of respect for the seven people who gave their lives for this research, I feel it's very important these results don't get lost"- Robert McLean.


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Clay made animal life possible on Earth, a University of California Riverside-led study finds. A sudden increase in oxygen in the Earth’s recent geological history, widely considered necessary for the expansion of animal life, occurred just as the rate of clay formation on the Earth’s surface also increased, the researchers report.

"Our study shows for the first time that the initial soils covering the terrestrial surface of Earth increased the production of clay minerals and provided the critical geochemical processes necessary to oxygenate the atmosphere and support multicellular animal life" - Martin Kennedy, associate professor of sedimentary geology and geochemistry at UCR, who led the study.

Study results appear in the Feb. 2 issue of Science Express, which provides electronic publication of selected Science papers in advance of print.
Analysing old sedimentary rocks, the researchers found evidence of an increase in clay mineral deposition in the oceans during a 200 million year period that fell between 1.1 to 0.54 billion years ago – a stretch of time known as the late Precambrian when oxygen suddenly increased in the Earth’s atmosphere. The increases in clay formation and oxygen shortly preceded – in geological time – the first animal fossils about 600 million years ago.

"This study shows how we can use principles developed from the study of modern environments to understand the very complex origin of life on our planet – studying a time in history that has left us only a scanty record of its conditions" - Lawrence M. Mayer, professor of oceanography at the University of Maine and a co-author of the Science paper.

Clay minerals form in soils through biological interactions with weathering rocks and are then eroded and flushed to the sea, where they are deposited as mud. Because clay minerals are chemically reactive, they attract and absorb organic matter in ocean water, and physically shelter and preserve it.
The UCR-led study emphasises the possibility that colonisation of the land surface by a primitive terrestrial ecosystem (possibly involving fungi) accelerated clay formation, as happens in modern soils. Upon being washed down to the sea, the clay minerals were responsible for preserving more organic matter in marine sediments than had been the case in the absence of clays. Organic matter preservation results in an equal portion of oxygen released to the atmosphere through the chemical reaction of photosynthesis. Thus an increase in the burial of organic carbon made it possible for more oxygen to escape into the atmosphere, the researchers posit.

"One of the things we least understand is why animals evolved so late in Earth history. Why did animals wait until the eleventh hour, whereas evidence for more primitive life dates back to billions of years? One of the best bets to explain the difference is an increase in oxygen concentration in the atmosphere, which is necessary for animal life and was likely too low through most of Earth’s history" - Martin Kennedy.

To establish a change in clay abundance during the late Precambrian, the researchers studied thick sections of ancient sedimentary rocks in Australia, China and Scandinavia, representing a history of hundreds of millions of years, to identify when clay minerals increased in the sediment from almost nothing to modern depositional levels.

"We predicted we would only find a significant percentage of clay minerals in sediments toward the end of the Precambrian, when complex life arose, while earlier sediments would have less clay content. This test is easier than it sounds. Because clay minerals make up the bulk of sediment deposited today, we are saying that it should be largely absent in ancient rocks. And this is just what one finds" - Martin Kennedy.

The study attracted the attention of the National Aeronautics and Space Administration during the proposal stage, and the agency helped fund the research.

“NASA is interested in what conditions to look for on other planets that might lead to the arrival of life. What are the processes? Using earth as our most detailed study site, what are the necessary steps a planet needs to go through to enable complex animal life to arise? If oxygen is the metabolic pathway, then we need to know what conditions have to allow for that to happen. The geologic record provides us with a record of these steps that occurred on Earth”- Martin Kennedy.

UCR’s Mary Droser and David Mrofka; and David Pevear collaborated on the study, which was supported also by the National Science Foundation.

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Arizona State University geochemist Dr Lynda Williams and her colleagues have discovered that certain clay minerals at the bottom of the ocean may have acted as incubators for the first organic molecules on Earth.
Primordial clay "wombs" that lie scattered around ocean floors played a crucial role in fostering early life on Earth. The clay structures were found in deep waters, in and around ocean floor volcanic vents called black smokers, so named because they churn out hot black particles from the Earth's crust.

By providing a haven for molecules brought up from the Earth's interior, the wombs protected them from the harsh environment until they formed the most basic building blocks of life. Black smokers form along the edges of mid-ocean ridges. The rich variety of chemicals they emit supports a unique ecosystem including bizarre bacteria and unique species of worms. Scientists believe that these hot, sulphur-rich waters may have been ideal for life to evolve.
Until now researchers have been puzzled as to how molecules such as methanol could have survived the 300 to 400 C temperatures in volcanic vents, but the researchers found that lumps of clay that build up on the inside walls of the vents could have captured, then protected, key molecules for around six months. The clay deposits eventually break away and spill out onto the ocean floor, where they break open, releasing the molecules into cool surrounding waters.


One of four pinnacles that form the summit of the 200-foot tall carbonate chimney called Poseidon in the Lost City hydrothermal field. The white chimney in the foreground is actively venting 55°C fluids. As the chimneys age they turn grey to brown in colour, such as the one shown towards the back. Image courtesy of University of Washington.

"When I first heard that, I thought, 'that's strange, Methanol is supposed to break down at those temperatures. I asked myself, 'what can protect it?' The answer is common clay minerals" - Dr Lynda Williams.

Dr Williams's group recreated the high temperature and pressure environment of a black smoker in the laboratory to examine whether organic molecules, the building blocks of life, could grow on various types of clay surface.

"We simulated the reactants that we know can exist in black smoker environments, to see what organic compounds would form in nature" - Dr Lynda Williams.

Six weeks into the experiment they discovered that one type of clay mineral, known as smectite, helped organic molecules to survive.
Smectite owes its protective properties to the layers of silicate it is formed from, allowing it to expand easily and let water, ions and molecules to flow inside.

"It is a bit like a peanut butter and jelly sandwich. The bread slices are the silicate layers, the sticky peanut butter represents the ions that are attracted to the bread and the jelly is like the organic compounds" - Dr Lynda Williams.

The rich chemical soup that rises through black smoker chimneys has all the right ingredients to form simple organic compounds, such as methanol. Dr Williams and her colleagues believe that clay stuck to the vent walls eventually gets pushed out of the chimney by flowing water, carrying the molecules inside to a safer place.

"If the organic compounds are released into cooler ocean water, which it is less acidic, some molecules might survive" - Dr Lynda Williams.

Similar womb-like structures may also exist on other planets, suggesting that the first step towards starting life may is not confined to Earth.

"This research tells us that as long as there is water and the right chemical ingredients, common clay minerals can help produce the ingredients for biomolecules (chemical components used by living organisms)" - Dr Lynda Williams.


The Mid-Atlantic Ridge hosts numerous hydrothermal fields (coloured dots). Lost City is currently the only known hydrothermal field composed solely of carbonate chimneys.
Logatchev, Rainbow and Saldahna are underlain by variable mixtures of deeper crustal rocks (gabbros and peridotite) and both Logatchev, Rainbow host high-temperature black smokers. The other fields are also sites of black smokers, but are hosted on volcanic rocks.
The Lost City Hydrothermal Field, lies about 762metres below the surface of the Atlantic Ocean.


Not everyone is convinced that Dr Williams's work, "Organic Molecules Formed in a Primordial Womb,"which appears in the November issue of Geology, explains how life on Earth got started. Mike Russell from the Centre for Life Detection at the California Institute of Technology, thinks life is more likely to have originated in a less extreme environment, such as the cooler hydrothermal springs, known as Lost City, discovered five years ago on the floor of the Atlantic Ocean. These warm springs also have all the necessary ingredients for the formation of organic carbon, but are only slightly hotter than human body temperature, so primordial wombs would not be needed to foster new life.

Additional experiments are planned to find out what chemical conditions would be required to form the building blocks of life.

"We have only started investigating the influence of clays on the origin of life" - Dr Lynda Williams

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Did life begin in ice?

New findings are backing up a theory that life originated in ice.
If it’s true, it could boost the chances that life might turn up in places considerably colder than our planet.
Ice might have been an ideal environment for the first self-replicating molecules, some researchers argue.

The theory departs from mainstream thinking on the origins of life, which usually assumes a warm, or hot, and wet environment was necessary.

"Conditions associated with freezing, rather than ‘warm and wet’ conditions, could have been of key importance" for the chemical reactions that led to life, wrote four researchers in the July 21 advance online issue of the Journal of Molecular Evolution, a research publication.

The scientists, including Laura F. Landweber of Princeton University in Princeton, N.J., argue that ice might have been a favourable environment to generate the first self-replicating molecules, a precondition for life.

These molecules would be of a type called ribonucleic acids, or RNA - a chemical cousin of DNA, which makes up genes.

Many researchers believe the first self-replicating molecule was RNA, not DNA. This is because RNA can do various things in addition to carrying genetic information, which is all that DNA basically does.

Some of RNA’s activities seem to be similar to what would be required for self-replication, something that DNA can`t do, strictly speaking. DNA needs the help of other molecules to copy itself. Also, RNA still exists in living cells, where it has various functions—some so basic to life that many scientists think RNA must have been there from the beginning.

The theory that RNA started it all, a 20-year-old proposal called the "RNA world hypothesis," holds that RNA was not only the first self-replicating molecule, but also that it initially carried out most of life’s functions, such as metabolism and cell formation.

Most biologists consider the RNA world hypothesis at least plausible, but it has some problems. It’s not easy to explain how the first self-replicating RNA molecules might have arisen.

RNA molecules tend to fall apart under warm conditions outside of cells. This would prevent the build-up of the rather long, complex RNA molecules that would probably be needed to conduct life processes, according to Landweber and her colleagues.

Various conditions can prevent RNA molecules` breakdown, the researchers argue. These include various types of water solutions, and freezing. But freezing may have been the one that most likely occurred on the early Earth, they argued.

Freezing usually slows down chemical reactions, which is why cold places are generally considered hostile to life. But freezing actually speeds up some of RNA’s key activities, Landweber and colleagues argue.

This is because ice contains hard, tiny compartments that hold the molecules in one place, where they can react together. Some of these reactions result in the creation of bigger RNA molecules.

In liquid water, by contrast, the molecules don`t come close enough together often enough to react as much. Thus they tend to fall apart faster than they can react to create bigger products.

In essence, the small compartments in ice play the role that cells today play in bringing the molecules together to react, Landweber and her colleagues argue. Dehydrated substances - a sort of primordial sludge, for instance - could also have provided a function similar to ice, they added, but ice works better.

Landweber’s group conducted an experiment to test the theory. Led by Alexander Vlassov of SomaGenics, a Santa Cruz, California - based biotechnology company, the researchers broke to pieces some RNA molecules found in normal cells. This process yielded more, smaller, RNA molecules.

By doing this, the researchers produced RNA molecules of sizes that biologists think might have been available on early Earth. They then experimented to find out what sort of capabilities these smaller RNAs had.

Reporting their results in the May 25, 2004 issue of the journal Nucleic Acids Research, the researchers noted that the broken-up RNAs still could carry out some of the same functions as normal RNAs, but only in ice or sometimes other extreme conditions, such as dehydration.

These activities included grabbing other pieces of RNA and attaching them together, an activity called `ligation` that is similar to self-replication.

To fully self-replicate, a molecule must attach other molecules together in such a way as to match the sequence of chemical pieces that characterize the first molecule. This process is called "template-directed" ligation.

But the ligation alone—even without the self-replication—can build up ever larger and more complex RNA molecules, which according to the RNA world hypothesis could eventually develop self-replicating abilities.

The theory that an icy environment might have helped jump-start life isn’t new. Researchers proposed in 1994, for example, that repeated cycles of freezing and thawing could help accelerate some of the chemical reactions necessary for life.

Such a scenario might have existed on early Earth, where according to some researchers, repeated meteor and comet impacts might have periodically melted an otherwise icy environment.

However, Landweber and her team seem to be the first to have provided an account of how the "RNA world" might have fit into this scenario, according to Leslie Orgel, an origins-of-life researcher at the Salk Institute for Biological Studies in San Diego, California.

The work "has important implications," said Jeffrey L. Bada, director of the NASA Specialized Centre in Research and Training in Exobiology in La Jolla, California, one of the original proponents of the freeze-thaw cycle theory.

Although Landweber and her colleagues also wrote that freeze-thaw cycles are helpful for the processes they describe, such cycles aren`’t strictly necessary in their proposal.

Moreover, they wrote in their Journal of Molecular Evolution paper, "It is worth noting that Jupiter’s moon Europa and even Mars are also thought to contain large amounts of liquid water and ice now or at some time in the past."

The possibility of RNA activities in ice, they added, "lends some credibility to claims that the rather extreme environments of these extraterrestrial locations could have provided suitable conditions for the emergence of life."

However, as Sergei Kazakov of Somagenics noted in an email, the origin of life and the RNA world aren’t necessarily the same thing.

"The RNA world as complex self-replicating molecular society could appear at multiple places in Universe, but not necessarily result in the appearance of life as we know it," he explained. This transition may actually be rare, he added.

"I also think that Earth is a possible but not necessarily the best place where the RNA world could start. Rather, I would bet on Europa or a giant comet," he continued. If the transition to life as we know it did occur, he added, "it could spread across many planets through cross-contamination" carried by comets or meteorites.

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