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Saturn moon resembles Earth at life’s birth, study finds

Nov. 6, 2006
Courtesy PNAS
and World Science staff

Ha­zy skies on ear­ly Earth, similar to those on Sat­urn’s moon Ti­tan, could have pro­vid­ed the ma­te­ri­al needed to form life, ac­cord­ing to a new stu­dy.

Ti­tan has a thick ha­zy lay­er of sub­stances known as or­gan­ic aerosols, car­bon-based chem­i­cals re­lat­ed to the in­gre­di­ents of liv­ing things.

Two lakes on Ti­tan, con­tain­ing what sci­en­tists be­lieve is a mix of carbon-based sub­stances eth­ane and meth­ane. The ra­dar im­age comes from the Cas­si­ni-Huy­gens mis­sion, a col­lab­o­ra­tion of NASA, the Eu­ro­pe­an Space Agen­cy and the Ital­ian Space Agen­cy. 
These com­pounds are be­lieved to be gen­er­at­ed from chem­i­cal re­ac­tions of mo­le­cules of meth­ane and ni­tro­gen high in Ti­tan’s at­mos­phere, stim­u­lat­ed by the sun’s ul­t­ra­vi­o­let rays. 

Mar­ga­ret Tol­bert of the Uni­ver­si­ty of Col­o­rad­o at Boul­der and col­leagues mim­icked Ti­tan’s chem­is­try by us­ing ultra­violet lamps in var­i­ous sim­u­lat­ed at­mos­pheres. 

The re­search­ers found that a meth­ane-ni­tro­gen mix would pro­duce var­i­ous types of large mo­le­cules known as long-chain hy­dro­car­bons. 

These, they re­ported, matched some of the known com­pounds ob­served by Huy­gens, a European-built probe that dropped on­to the smog-shrouded world last year.

The re­search­ers al­so tested at­mos­pheres that might have re­sem­bled ear­ly Earth, con­tain­ing meth­ane and car­bon di­ox­ide. These con­di­tions gave rise to a haze con­tain­ing a dif­fer­ent but re­lat­ed set of long-chain com­pounds, in­clud­ing chem­i­cals known as alde­hy­des and ethers, they said.

The re­search­ers cal­cu­late that Earth could have pro­duced over 100 mil­lion tons of such ma­te­ri­al each year, and it could have served as the pri­ma­ry source ma­te­ri­al for prim­i­tive life. The find­ings are pub­lished in this week’s ear­ly on­line edi­tion of the re­search jour­nal Pro­ceed­ings of the Na­tio­n­al Aca­de­my of Sci­en­ces.

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Homepage image: a crescent Titan as viewed by NASA's Voyager 2 mission in 1981.

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Hazy skies on early Earth, like those on Saturn’s moon Titan, could have provided the material needed to form life, according to a new study. Titan has a thick hazy layer of substances known as organic aerosols, chemicals related to the ingredients of living things. These compounds are believed to be generated from chemical reactions molecules of methane and nitrogen high in Titan’s atmosphere, reactions stimulated by ultraviolet light from the sun. Margaret Tolbert of the University of Colorado at Boulder and colleagues mimicked Titan’s chemistry by using ultraviolet lamps in various simulated atmospheres. The researchers found that a methane-nitrogen mix would produce various types of large molecules known as long-chain hydrocarbons. These, they reported, matched some of the known compounds observed by Huygens, a European-built probe that dropped onto the smog-shrouded world last year. The researchers also tested atmospheres that might have resembled early Earth, containing methane and carbon dioxide. Under these conditions, a haze containing a different but related set of long-chain compounds, including chemicals known as aldehydes and ethers, was produced, they said. The researchers calculate that Earth could have produced over 100 million tons of such material each year, and it could have served as the primary source material for primitive life. The findings are published in this week’s early online edition of the research journal pnas.