杏吧原创

THE idea that our planet鈥檚 earliest life forms arrived from space has been
boosted by the discovery that a stream of charged particles鈥攕imilar to the
鈥渨ind鈥� that continually blows from the Sun鈥攎ay cause reactions that could
lead to life. In lab tests the particle stream transformed simple chemicals into
complex biological molecules.

Some researchers think the building blocks of life were brought to Earth by
comets. Now Lubomir Gabla and his colleagues at the Jagiellonian University in
Cracow, Poland, have shown how they may have formed on grains of space dust.

Gabla鈥檚 team simulated space dust with a thin layer of anthracene on a
gold-plated surface. Anthracene is a simple organic compound commonly found in
comets, meteorites and space dust. The team cooled the simulated dust to a
space-like 150 kelvin and sprayed it with water vapour to provide the moisture
also found on space dust.

To mimic the bombardment of solar wind particles, the team fired a beam of
protons at the surface. After the equivalent to 100 years of solar wind, the
team found a yellowish-brown crust covering the anthracene. This crust included
quinones鈥攁 class of molecule that is present in most organisms and plays
an important part in many biological processes. 鈥淲e鈥檝e produced the primary
material for building complex organic molecules,鈥� Gabla says.

He adds that protons would penetrate a comet鈥檚 surface by less than a
micrometre, having little impact on its composition. But dust grains are so tiny
that protons reach right to their cores.

Planetary scientist Mark Burchell of the University of Kent in Canterbury
says that while the team has simulated the formation of such molecules in space,
we don鈥檛 know if they would survive. 鈥淲hat would be good would be to collect
dust samples in space and analyse them,鈥� Burchell says.