One nitrogen atom, three hydrogen atoms. That’s all it takes to make the basic ammonia molecule. This simple compound was one of the most important building blocks for the origin of life, scientists believe, providing the nitrogen that is crucial to many organic compounds. They just don’t know for sure how so much of it could form under the conditions of the early Earth.

In a new study this week, Sandra Pizzarello and colleagues tie the ammonia surplus to one of the more fascinating theories about the rise of life—that some of its basic components seeded the Earth from space on board meteorites that pounded the planet’s surface.

Pizzarello’s team analyzed a particular meteorite found in Antarctica. Its name is Graves Nunataks (GRA) 95229, and it was discovered in 1995. But its important characteristic is that the it belongs to a class of meteorites called carbonaceous chondrites that are full of organic materials. In the lab, the researchers tried to simulate how those materials in GRA 95299 might have reacted when they reached the younger Earth.

Pizzarello and her co-authors subjected a sample of the meteorite … to temperatures of 300 degrees Celsius at high pressures in the presence of water to simulate hydrothermal conditions on the meteorite’s parent asteroid or on Earth. Under heat and pressure, GRA 95229 released almost nothing but ammonia, in amounts that constitute roughly 1 percent by mass of the type of meteoritic material examined. Its parent asteroid, the authors speculate, must have been rich in ammonia. [Scientific American]

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Nick Lane’s book Life Ascending: The Ten Great Inventions of Evolution has just won the Royal Society’s science book prize. The book chronicles the history of life on Earth through ten of evolution’s greatest achievements, from the origins of life itself to sex, eyes, and DNA.

The judges said that the ease with which Lane communicates these complex scientific ideas is what makes the book shine.

“Life Ascending is a beautifully written and elegantly structured book that was a favourite with all of the judges. Nick Lane hasn’t been afraid to challenge us with some tough science, explaining it in such a way that we feel like scientists ourselves, unfolding the mysteries of life,” said Maggie Philbin, chair of the judges. [The Guardian]

Instead of dumbing down the science, Lane’s words build the reader up to an understanding of evolution’s work.

Lane is a superb communicator. He knows exactly how much technical detail is required to provide satisfying explanations for the evolution of the genetic code, photosynthesis, complex cells, muscles and eyes, and his enthusiasm is catching. [The Guardian's book review]

Lane, a biochemist himself at University College London, believes in what he writes about. He studies and formulates hypotheses about the evolution of life for his job, and loves to communicate these ideas.

“Writing is my way to understand the world. I tried to get across the boundary between what we know and what we don’t know,” Lane explained. “It’s a thrilling tapestry that writing can take you across – you can ask any question you want, but there’s responsibility that goes with that.” [Nature]

Alas, this may be the last year of the prestigious book prize. It lost its sponsor, pharmaceutical company Aventis, in 2007, and has run out of funds.

Related content:
Not Exactly Rocket Science: The origin of complex life – it was all about energy
Not Exactly Rocket Science: A possible icy start for life
The Loom: Book (P)review #1: Life Ascending, The Ten Great Inventions of Evolution
The Loom: Microcosm On the Longlist for Royal Society Science Book Prize (Along With A Dozen Great Books)
The Intersection: Everyday Practice of Science

Image: W. W. Norton & Company

From Ed Yong:

The origin of life is surely one of the most important questions in biology. How did inanimate molecules give rise to the “endless forms most beautiful” that we see today, and where did this event happen?  Some of the most popular theories suggest that life began in a hellish setting, in rocky undersea vents that churn out superheated water from deep within the earth. But a new paper suggests an alternative backdrop, and one that seems like the polar opposite (pun intended) of the hot vents –ice.

Like the vents, frozen fields of ice seem like counter-intuitive locations for the origin of life – they’re hardly a hospitable environment today. But according to James Attwater form the University of Cambridge, ice has the right properties to fuel the rise of “replicator” molecules, which can make copies of themselves, change and evolve.

Read the rest of this post at Not Exactly Rocket Science. And for more about the possibly frigid origins of life—and the implications of that for finding life beyond Earth—check out the DISCOVER feature “Did Life Evolve in Ice?”

More Related Content:
Not Exactly Rocket Science: Tree Or Ring: The Origin of Complex Cells
80beats: Earth Raised up Its Magnetic Shield Early, Protecting Water and Emerging Life
80beats: Dust Collected From Comet Contains a Key Ingredient of Life

Image: Wikimedia Commons

Sponges are just about the simplest animals on the Earth. And they might be the oldest ones we know, too.

Adam Maloof and colleagues published a study in Nature Geoscience this week about their find that could push back the oldest known animal life by 70 million years. In Australia, Maloof says, the team found remains of ancient sponges dating to about 650 million years ago.

The prior oldest known hard-bodied animals were reef-dwelling organisms called Namacalathus, which date to approximately 550 million years ago. Disputed remains for other possible soft-bodied animals date to between 577 and 542 million years ago [Discovery News].

At 650 million years old, the sponges would predate the Cambrian Explosion—a huge blossoming of diversity in animal life—by 100 million years. These organisms would also predate an intense moment in our planet’s history known as “Snowball Earth,” according to paleobiologist Martin Brasier. It’s even possible that they helped cause it.

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You can’t rise from the primordial ooze if that ooze is frozen. But about three billion years ago the sun was around thirty percent dimmer, meaning our planet should have been a snowball. The puzzle has haunted scientists for decades, but a study in Science has a new answer: It argues that a dense cloud of “fractal haze” enveloped the Earth.

Old Theories

This isn’t the first attempt to solve the early Earth conundrum. Carl Sagan, for one, had a few ideas. First, in 1972, he speculated that the atmosphere had ammonia which could trap heat, but later work showed that the sun’s ultraviolet radiation would have broken that ammonia down. In 1996 he tried again, saying that Earth might have had a thick haze, perhaps a nitrogen-methane mix, that blocked the ultraviolet but let in enough of the sun’s then-meager rays to warm the planet. Unfortunately, that too was a no go:

Early models assumed the haze particles were spheres, and that when individual particles collided, they globbed together to make bigger spheres. These spheres blocked visible light as well as ultraviolet light, and left the Earth’s surface even colder. “It basically led us to a dead end where we couldn’t have a warm early Earth,” said Eric Wolf, a graduate student in atmospheric sciences at the University of Colorado at Boulder and the first author of the new study. [Wired]

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There are millions of asteroids in the asteroid belt between Mars and Jupiter, but yesterday attention focused on just one. According to a couple of studies in Nature, a large asteroid called 24 Themis is rife with water ice and organic molecules, and the researchers say that it could be more evidence that the water so precious to life on Earth came to our planet on board such rocks.

Two research teams took infrared images of 24 Themis, which is about 120 miles in diameter and was discovered in 1853. This asteroid has an extensive but thin frosty coating. It is likely replenished by an extensive reservoir of frozen water deep inside rock once thought to be dry and desolate [AP].

The team, led by Humberto Campins, says finding so much ice on the surface was a surprise; at the asteroid’s distance from the sun—3.2 astronomical units (AU), or just more than three times further than the Earth—exposed ice has a “relatively short lifetime,” the scientists write. As a result, the idea of a below-surface reservoir seems likely. (Icy comets aren’t nearly so close to the sun on average; Halley’s comet can come within .6 AU of the sun, but then retreats to a farthest distance of more than 35 AU.)

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The “young sun paradox” just won’t go away. For decades, scientists like Carl Sagan have tried to resolve this mystery of the early solar system—how the newborn Earth stayed warm enough to keep liquid water—but it continues to bob and weave around an answer. In the journal Nature, a team led by Minik Rosing proposes an alternate solution to the leading theory, which relies on the greenhouse effect hypothesis. But don’t expect the debate to end here.

The problem is this: The young Earth received much less heat from the sun. Four billion years ago, a lower solar luminosity should have left Earth’s oceans frozen over, but there is ample evidence in the Earth’s geological record that there was liquid water — and life — on the planet at the time [Space.com]. So what gives? The traditional explanation going back to the 1970s has been that a powerful greenhouse effect, far stronger than the one we experience today, kept the Earth basked in enough warmth to keep water sloshing around the planet’s surface as a liquid and not packed in solid ice. In 1972, Sagan and colleague George Mullen wrote that such an effect would have required intense carbon dioxide concentrations in the atmosphere during that period, the Archaen.

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Here we are drinking coffee and tweeting and otherwise going about our lives, generally not giving much thought to the protection that the Earth’s magnetic field affords us from the solar wind. But that magnetic field is crucial for our existence. Now, new findings in Science say that this protective shield originated even 200 million years earlier than scientists had previously thought, perhaps protecting the planet’s water from evaporating away and aiding the rise of life on the early Earth.

To know about the planet’s magnetic field three and a half billion years ago, you need iron, which records not only the direction but also the strength of the magnetic field when it forms. In South Africa, study leader John Tarduno and his team found quartz with iron tucked inside that had remained unchanged in all those years. Using a specially designed magnetometer and improved lab techniques, the team detected a magnetic signal in 3.45-billion-year-old rocks that was between 50 and 70 percent the strength of the present-day field, Tarduno says [Science News]. Three years ago he made a similar find in rocks 3.2 billion years old; thus, this find pushes back the Earth’s magnetic field at least another 200 million years.

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One of the building blocks of life has been found on a comet hurtling through the solar system, adding evidence to the theory that earthly biology began when comets and meteors bombarded our young planet and seeded it with the precursors of life. The amino acid, glycine, was found in a sample returned by the space probe Stardust that buzzed by the comet Wild 2 in 2004. The probe swept up particles fizzing off the object’s surface as it passed some 240km (149 miles) from the comet’s core, or nucleus. These tiny grains, just a few thousandths or a millimetre in size, were then returned to Earth in 2006 in a sealed capsule [BBC News].

Amino acids are crucial to life because they form the basis of proteins, the molecules that run cells. The acids form when organic, carbon-containing compounds and water are zapped with a source of energy, such as photons – a process that can take place on Earth or in space [New Scientist].

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How life evolved from a mix of chemicals on the young planet Earth is one of science’s most enduring mysteries, which biochemists are attempting to solve by recreating the earliest building blocks of life in the laboratory.

Earth’s biology is based on DNA, which carries all an organism’s genetic information in a molecule that takes the shape of a spiraling ladder. RNA, the molecule that facilitates protein manufacturing, has a simpler shape–it’s a single strand, as opposed to DNA’s double strand–leading some biologists to propose the RNA world hypothesis in which RNA evolved first and eventually gave rise to DNA. But trying to imagine the assembly of RNA from its chemical components poses its own problems. How could RNA, which encodes proteins, first form, when proteins are needed for [its] synthesis? Now, scientists report that they’ve cooked up molecular hybrids of proteins and nucleic acids that skirt the dreaded paradox [ScienceNOW Daily News].

The hybrids they created could resemble the precursors to RNA, researchers report in Science. “It’s the pre-RNA world. There’s a hypothesis that says RNA is so complicated, it couldn’t have arisen de novo” — from scratch — “on early Earth,” said study co-author Luke Leman…. “So you need some more primitive genetic system that nature fiddled around with and finally decided to evolve into RNA” [Wired.com].

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Left-handed people may be in the minority, but left-handed amino acids rule the Earth. Researchers have long known that the building blocks of proteins can be constructed in either “left-handed” or “right-handed” versions that are mirror images of each other, but that almost every living organism on Earth uses left-handed amino acids. Now, a new study gives weight to a theory of how that preference came to pass. NASA researchers examined meteorites that predate the Earth’s formation, and say that those early rocks also have a preponderance of left-handed molecules. “Meteorites would have seeded the Earth with some of the prebiotic compounds like amino acids that are needed to get life started, and also biased the origin of life to the left-handed amino acid form,” says [study coauthor] Daniel Glavin [New Scientist].

Researchers note that if you make amino acids from scratch in a lab using their chemical components, you inevitably get half of the right-handed version and half of the left handed version. So it might be expected that if nature makes amino acids in space using similar chemistry, you’d also get a fifty-fifty mixture [CBC]. Yet that’s not what Glavin and his colleagues found when they studied the molecular deposits in six meteorites that are more than 4.5 billion years old. Instead, they found the ratio of amino acids tilted toward left-handedness in all six specimens. In one of the rocks, the imbalance was 18%, the largest ever reported for a meteorite. “I have to admit I didn’t believe it at first,” Glavin says [ScienceNOW Daily News].

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By tweaking chemical strands of RNA, researchers have taken another step towards understanding how life may have first evolved on our planet. A test tube based system of chemicals that exhibit life-like qualities such as indefinite self-replication, mutation, and survival of the fittest, has been created by US scientists…. “This is the very end of the line, where chemistry starts turning into biology” [Chemistry World], says researcher Gerald Joyce. Researchers have previously created RNA strands that replicated themselves for a while before grinding to a halt, but this experiment marks the first creation of RNA strands that continue to replicate themselves indefinitely, which set up the conditions that allowed for evolution.

In the modern world, DNA carries the genetic sequence for advanced organisms, while RNA is dependent on DNA for performing its roles such as building proteins. But one prominent theory about the origins of life, called the RNA World model, postulates that because RNA can function as both a gene and an enzyme, RNA might have come before DNA and protein and acted as the ancestral molecule of life [Astrobiology Magazine].

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Over 4 billion years ago the young and barren Earth was being buffeted by meteor strikes, and that violent bombardment could have created the first amino acids that then gave rise to the origin of life on the planet, a new study suggests. The hellish temperatures and pressures generated when an extraterrestrial object strikes Earth at speeds of several kilometers per second are enough to shatter and vaporize rock…. Yet part of such an immense burst of energy can trigger chemical reactions that generate complex organic substances from basic inorganic ingredients, says Takeshi Kakegawa [Science News].

Previously, researchers have suggested that organic molecules may have been created elsewhere in the universe and were brought to Earth by meteors. But the new study, in which researchers simulated the impact of meteorites in the primordial ocean, argues that the organic molecules could have been synthesized from the inorganic molecules already present on the planet when the meteorites crashed into the ocean. Other researchers have suggested similar processes for the creation of organic molecules on Earth, including lightning strikes or chemical reactions surrounding hot, volcanic vents in the deep sea.

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The evolution of minerals on our planet has been propelled by the evolution of life on earth, a sweeping new study demonstrates. While the underlying assumption isn’t new, the study is the first to chart how the emergence of algae and then complex microorganisms gave rise to the 4,300 or so minerals that are now present on earth.

In the early days of the universe, clouds of gas and dust contained all the naturally occurring elements found in the periodic table, but most were too widely dispersed to form minerals; scientists believe there were only about a dozen minerals in the interstellar medium. According to the study, around a further 60 different minerals formed 4.5 billion years ago, as clumps of matter collided and coalesced to begin forming the Solar System. The smaller fragments congealed into larger, planet-sized bodies, where volcanism and the effects of water took the mineral count into the hundreds. The planets Mars and Venus have got this far [Nature News], and have minerals created by hot magma like quartz and zircon.

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Vials holding the results of a famous chemistry experiment conducted 55 years ago have been discovered in dusty cardboard boxes, and a new analysis of their contents has revealed fresh insights into a big question: the origin of life on earth. In 1953, chemist Stanley Miller tried to duplicate the conditions present on the primordial earth in laboratory flasks, and while some of his results were published to great acclaim, other results were packed away and forgotten–until now.

Miller’s classic experiment involved putting atmospheric components thought to reflect those of the early Earth (ammonia, hydrogen, methane, and water) in a closed system and stimulating that mixture with an electric current to mimic the effects of lightning storms. He generated a small number of biochemically significant compounds, including amino acids, hydroxy acids, and urea, showing that conditions of primitive earth can create the building blocks of life [Ars Technica]. These results generated considerable excitement, but later researchers argued that Miller was wrong about the composition of the young earth’s atmosphere, and the experiment was written off as a novelty.

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