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201306Apr11:40

Power behind pri­mor­dial soup discovered

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pub­lished 06 April 2013 | mod­i­fied 05 April 2014
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Image credit: ©James McKay 2013 www.jamesmckay.infoResearchers 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 build­ing blocks 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 liq­uids around vol­ca­noes, which were likely to have been com­mon across the early Earth. The paper was pub­lished online by the jour­nal Geochim­ica et Cos­mochim­ica Acta on 15th March 2013.

The mys­tery of how liv­ing organ­isms sprung out of life­less rock has long puz­zled sci­en­tists, but we think that the unusual phos­pho­rus chem­i­cals we found could be a pre­cur­sor to the bat­ter­ies that now power all life on Earth. But the fact that it devel­oped sim­ply, in con­di­tions sim­i­lar to the early Earth, sug­gests this could be the miss­ing link between geol­ogy and biology
(Dr Terry Kee, research team­leader, Uni­ver­sity of Leeds’ School of Chemistry)

All life on Earth is pow­ered by a process called chemios­mo­sis, where the chem­i­cal adeno­sine triphos­phate (ATP), the recharge­able chem­i­cal ‘bat­tery’ for life, is both bro­ken down and re-​formed dur­ing res­pi­ra­tion to release energy used to drive the reac­tions of life, or metab­o­lism. 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 chem­i­cal reac­tiv­ity. 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.


(Source: Uni­ver­sity of Leeds press release, 04.04.2013)

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