Comets - the seeds of life?

Scientists in astrobiology, also known as exobiology, seek the answer to that question by examining and analyzing comets that have been in our solar system for millions of years. They’ve made some astonishing discoveries.

Several comets and meteorites, principally the Murchinson meteorite, have been found to contain amino acids and sugar groups, which are the constituents of DNA, the core of life. The ALH84001 meteorite from Mars is even more amazing. In addition to the same fundamental “building blocks” as found in the Murchinson meteorite, it contains structures resembling fossilized microorganisms. These finds raise the question as to whether life could have started on another planet and have been carried to Earth on a comet.

Comets consist mostly of water and often are called “dirty snowballs”. There are some theories that all our water came from comets that collided with the Earth long ago. These comets could also have brought the essential building blocks of life, the prebiotic chemicals. So, astrobiologists are as concerned with comets as with remote planets.

Three space missions are now conducting comet research. In January 2004, the Stardust probe will fly close to the Wild 2 comet and take samples of material and dust from it back to Earth for analysis. The Muses probe will land a small rover on the Nereus comet to collect a sample for return to Earth. The Rosetta probe carries two landing units, Champollion and Roland that will land on a comet in 2012 and follow it in toward the Sun.