NEW YORK: Perception among scientists that comets were responsible for creating life on Earth got further substantiation with the finding of complex carbon-rich molecules in the material that NASA's Stardust mission scooped up from comet Wild-2 in 2004.
Scientists now strongly believe these molecules could hold the key to the series of reactions that took place at the time of planet forming, which ultimately gave the Earth its present biochemical mould.
While the subject of how life originated on the Earth is subject of intense study, there are scientists who believe that when comets repeatedly struck earth, they deposited several chemicals, which led to bio-chemical reactions.
The Stardust spacecraft had passed past Wild-2 in January 2004 -- around 240 kms from its core -- and captured particles getting thrown out of its surface. These tiny particles were returned to Earth in sealed capsules, which were later subjected to detailed studies at some 50 research laboratories across the world. As scientists collate information from these studies, they are getting to know the conditions that prevailed in the earliest phases of the evolution of the solar system.
Dr Scott Sandford of the NASA's Ames Research Center, who led the organics investigation with some 55 researchers in more than 30 institutions, found that there were many delicate, volatile compounds in the sample unlike in materials found in meteorites that have fallen on Earth.
Sandford believes that these compounds could be organic population of molecules that were made when ices in the dense cloud from which the solar system formed were irradiated by ultraviolet photons and cosmic rays.
He says in laboratory simulations, such processes produce a lot of organic compounds, including amino acids and a class of compounds called amphiphiles, which when put in water spontaneously form a membrane so that they make little cellular-like structures.
The particles from Wild-2 are also expected to help researchers to refine the models they use to describe how materials were moved and mixed up in the early solar system.
According to preliminary findings, the materials are essentially mineral grains which show a huge diversity, and more interestingly, these are found to have been incorporated into the samples that must have formed close to the proto-Sun. These include fragments of calcium-aluminium and magnesium-olivine.
Dr Don Brownlee of the University of Washington and principal investigator of the Stardust mission, says these particles are formed in the hottest possible place in the solar system and hence it is quite surprising that they are found in a body that came from the coolest of place in the solar system.
Meanwhile, scientists speaking at a meeting of the American Geophysical Union, said they believe there could be some mixing of the material happening in the early solar system to send material from the proto-Sun into deep space and these could have been picked up by comets.
Such a situation can drastically change theories about how stars and the surrounding planets formed from the primordial dust and gas, they said.
The scientists' findings on the Wild-2 material are reported on Science Express.
