The theory that life arrived on Earth on the back of a comet is much closer to being universally accepted now thanks to research in which Italian scientists played an important role.
Astrophysics experts in Naples found molecules they called the "basic building blocks of life" in dust from a comet that a NASA space probe brushed past almost three years ago.
The results of the tests, along with those from other laboratories around the world, were published on Friday. Three of the seven articles in the prestigious American journal Science were penned by Italian experts.
University of Naples researcher Alessandra Rotundi, who coordinated the Italian team, said she found traces of life-sustaining amino acids in the particles from the Wild 2 comet's tail.
There were also long chains of carbon molecules, which are known to be indispensable for life, along with oxygen and nitrogen, two elements which were crucial in the development of the earth's life-supporting atmosphere.
"This is direct confirmation of the theory that molecules brought by a comet laid the foundations for the origin of life on Earth," Rotundi said.
Scientists are practically certain that a heavy bombardment of comets hit the Earth some 3.9 billion years ago.
This, together with the fact that fossils of the first life forms date back to 3.8 billion years ago, has led many scientists to conclude that comets played a role in the beginnings of life.
But until now there was no objective evidence of this. Rotundi cautioned that even the discoveries in the space dust from Wild 2, intercepted 389 million km away from earth, do not amount to definitive proof.
It is however a "big step" in that direction, she said.
The NASA space capsule carrying about a hundred grains of matter from the comet returned to earth last January, two years after it whizzed through Wild 2's tail at about 21,000 km/h.
The grains were divided up and sent to laboratories around the world for analysis. The universities of Naples, and Catania received some particles, as did the INAF national astrophysics institute at Capodimonte, Naples.
The tiny particles, each one five times smaller than the diameter of a human hair, were the first rock samples to arrive on earth from the solar system in 34 years.
The last ones were moon rocks brought back by the Apollo 17 mission in 1972.
