Power behind primordial soup discovered

Apr 04, 2013

(Phys.org) —Researchers at the University of Leeds may have solved a key puzzle about how objects from space could have kindled life on Earth.

While it is generally accepted that some important ingredients for life came from meteorites bombarding the early Earth, scientists have not been able to explain how that inanimate rock transformed into the of life.

This new study shows how a chemical, similar to one now found in all living cells and vital for generating the energy that makes something alive, could have been created when meteorites containing phosphorus minerals landed in hot, acidic pools of around volcanoes, which were likely to have been common across the early Earth.

"The mystery of how sprung out of lifeless rock has long puzzled scientists, but we think that the unusual phosphorus chemicals we found could be a to the batteries that now power all . But the fact that it developed simply, in conditions similar to the early Earth, suggests this could be the missing link between and biology," said Dr Terry Kee, from the University's School of Chemistry, who led the research.

All life on Earth is powered by a process called chemiosmosis, where the chemical adenosine triphosphate (), the rechargeable chemical 'battery' for life, is both broken down and re-formed during to release energy used to drive the reactions of life, or . The complex enzymes required for both the creation and break down of ATP are unlikely to have existed on the Earth during the period when life first developed. This led scientists to look for a more basic chemical with similar properties to ATP, but that does not require enzymes to transfer energy.

Phosphorus is the key element in ATP, and other fundamental building blocks of life like DNA, but the form it commonly takes on Earth, phosphorus (V), is largely insoluble in water and has a low . The early Earth, however, was regularly bombarded by meteorites and interstellar dust rich in exotic minerals, including the far more reactive form of phosphorus, the iron-nickel-phosphorus mineral schreibersite.

The scientists simulated the impact of such a meteorite with the hot, volcanically-active, early Earth by placing samples of the Sikhote-Alin meteorite, an iron meteorite which fell in Siberia in 1947, in acid taken from the Hveradalur geothermal area in Iceland. The rock was left to react with the acidic fluid in test tubes incubated by the surrounding hot spring for four days, followed by a further 30 days at room temperature.

In their analysis of the resulting solution the scientists found the compound pyrophosphite, a molecular 'cousin' of pyrophosphate – the part of ATP responsible for energy transfer. The scientists believe this compound could have acted as an earlier form of ATP in what they have dubbed 'chemical life'.

"Chemical life would have been the intermediary step between inorganic rock and the very first living biological cell. You could think of chemical life as a machine –a robot, for example, is capable of moving and reacting to surroundings, but it is not alive. With the aid of these primitive batteries, chemicals became organised in such a way as to be capable of more complex behaviour and would have eventually developed into the living biological structures we see today," said Dr Terry Kee.

The team from NASA's Jet Propulsion Laboratory (JPL-Caltech) working on the Curiosity rover, which landed on Mars in August last year, has recently reported the presence of phosphorus on the Red Planet.

"If Curiosity has found phosphorus in one of the forms we produced in Iceland, this may indicate that conditions on Mars were at one point suitable for the development of life in much the same way we now believe it developed on Earth," added Dr Kee.

The team at Leeds are now working with colleagues at JPL-Caltech to understand how these early batteries and the 'chemical life' they became part of might have developed into biological life. As part of this work they will be using facilities in the University of Leeds' Faculty of Engineering, currently used to test new fuel cells, to build a 'geological fuel cell' using minerals and gases common on the early Earth. Researchers will apply different chemicals to its surface and monitor the reactions take place and the chemical products which develop.

The team also hope to travel to Disko Island in Greenland which is home to the Earth's only naturally-occurring source of schreibersite, the mineral found in the Sikhote-Alin meteorite. Here, they hope to repeat their experiments and show that the same chemicals develop in an entirely Earth-originated setting.

The paper Hydrothermal modification of the Sikhote-Alin iron under low pH geothermal environments. A plausibly prebiotic route to activated phosphorus on the was published online by the journal Geochimica et Cosmochimica Acta on March 15, 2013.

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More information: David E. Bryant, David Greenfield, Richard D. Walshaw, Benjamin R.G. Johnson, Barry Herschy, Caroline Smith, Matthew A. Pasek, Richard Telford, Ian Scowen, Tasnim Munshi, Howell G.M. Edwards, Claire R. Cousins, Ian A. Crawford, Terence P. Kee, Hydrothermal modification of the Sikhote-Alin iron meteorite under low pH geothermal environments. A plausibly prebiotic route to activated phosphorus on the early Earth, Geochimica et Cosmochimica Acta, Volume 109, 15 May 2013, Pages 90-112, ISSN 0016-7037, DOI:10.1016/j.gca.2012.12.043. http://www.sciencedirect.com/science/article/pii/S0016703713000161

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Moebius
1 / 5 (5) Apr 04, 2013
Trying to find the origin of life without knowing what the first life is would be like trying to find Everest without knowing what a mountain is. The first life could not have had DNA unless you believe in genesis. So what was it then that had the capability to evolve DNA? The easiest way to find out how it started is to find some if it if it still exists.
Whydening Gyre
2.3 / 5 (3) Apr 04, 2013
Just a little correction. Phosphorus is NOT Vanadium...
Whydening Gyre
4 / 5 (8) Apr 04, 2013
And to answer your question, Moebius - CHNOPS are all elements responsible for the huge number of amino acids required to build "life". They are SELF organizing due to the way the charges in their valence shells interact/add together. Everything we observe in our Universe is the cumulative result of a "plus 1" action that occurred before it...
The "God" everybody wants to blame for all things good and bad, is an adding machine with the "add" button stuck on...
Silverhill
5 / 5 (2) Apr 04, 2013
Just a little correction. Phosphorus is NOT Vanadium...
I think they mean phosphorus(V), the pentavalent form of the element. The mono-, di-, tri-, and tetravalent states are apparently more reactive.
Torbjorn_Larsson_OM
5 / 5 (3) Apr 04, 2013
This is great for the RNA world, but recent phylogenetic works points to the chemistry of alkaline hydrothermal vents as the redox energy sources. Lane & Martin has shown that the inherent pH modulation makes H+/Na+ transport the immediate ancestor to phosphate energetics. [The Origin of Membrane Bioenergetics, Lane&Martin, Cell 2012] And fold family phylogenies tests that this metabolism was earliest. [The evolutionary history of protein fold families ..., Kim & Caetano-Anollés, BMC Evol Biol 2012]

I think a hybrid scenario is the most likely pathway, akin to L&Ms model of early replicators. The G et C Acta paper supports how apatites end up making phosphates under geothermal conditions. Even Moon rocks contains apatite.

Sure, the then frequent impactors likely helped.
Torbjorn_Larsson_OM
5 / 5 (3) Apr 04, 2013
@Moebius: I don't understand your basis for analysis: astrobiology has known that the RNA world was the immediate root to the DNA LUCA since the 70's!

RNA is the solution to the chicken-and-egg problem of protein-DNA cell machinery that several people got Nobel prizes for. (Discovery of RNA ribozyme as the central preserved core in the protein factory ribosome.)

1. DNA is metabolically produced out of RNA. ATP and NADH, nucleotide coenzymes, are universal metabolic energy currency. (Root of metabolism machinery.) 2. mRNA, tRNA and rRNA is all that is needed to make proteins that make DNA out of. (Root of genetic machinery.) 3. Universal membrane tagging machinery is rooted in RNA. (Root of membrane machinery.)
Torbjorn_Larsson_OM
5 / 5 (1) Apr 04, 2013
[cont] Uniquely, RNA can form replicators without protein energetics. (Fulfills the thermodynamic bound.)

They also crystallize to replicator strands out of unordered strands by thermodynamic forcing in the presence of vent phosphates in some 10s of thousands of years, computer experiments have verified that.

They are both able to form genetic material and enzymes (ribozymes).

Finally, RNA strands can resist higher temperatures than DNA but are less chemically stable, indicating chemical to biological evolution under early hot (bombarded) but as of yet lifeless (well, duh!) Earth. If life already existed and attacked chemically, we would instead expect to see DNA first, RNA later, so we know we have the order correct.
Torbjorn_Larsson_OM
5 / 5 (1) Apr 04, 2013
[cont] Original RNA cells have gone extinct, as has the descended generic DNA LUCA variants with their shared protein fold family repertoire, we have only the modern more specialized cell domains left.

But presumably some RNA viruses can be RNA cell descendants, akin to how some large double stranded DNA viruses are parasite simplifications descended out of later DNA cells. We just haven't found them yet, too few sequenced viruses and parasites suck making phylogenies out of (very specialized, much gene and trait loss).

Even so, we now know the approximative pathway taken by independent ways of testing earlier proposed likely pathways. Astrobiology is maturing from descriptive to well tested science.
humy
not rated yet Apr 05, 2013
There are several serious flaws with this article.

Firstly, there is absolutely NO rational reason to believe that important ingredients for life probably came from meteorites in particular -this is a baseless idea since physical simulations of the Early Earth show that complex organic chemicals would have spontaneously formed in oceans etc with or without meteors just fine and, in addition, the amounts of such organic chemicals coming from meteors would be about in the order of perhaps ~one billion times less than the amounts that spontaneously formed on Earth.

Secondly, it suggests that the more reactive forms of phosphorus needed to make ATP and DNA may have come from meteors. But the first life almost certainly didn't have either ATP nor DNA (too complex -so it must have evolved later) thus this would NOT explain the origins of the first life!

humy
5 / 5 (1) Apr 05, 2013

---continued---

Thirdly, it said: "You could think of chemical life as a machine –a robot, for example, is capable of moving and reacting to surroundings, but it is not alive." which is total nonsense because ALL life can be thought as a " machine –a robot, for example, is capable of moving and reacting to surroundings" at least providing it can sustainably grow and reproduce. There is absolutely no rational in arbitrarily adding an energy-carrying substance such as ATP to be part of life for it to be defined as 'truly' alive. They don't know what they are talking about here.
tkjtkj
not rated yet Apr 13, 2013
Trying to find the origin of life without knowing what the first life is would be like trying to find Everest without knowing what a mountain is.


Was it Justice Frankfurter who was reported as saying something similar?.." i dont know what pornography is, but i know it when i see it!" ...
Isnt everything in the universe unnamed until discovered? Would not knowing what radiation is prevent its discovery and practical uses?

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