Comets... the universe's Johnny Appleseed?
On January the 2nd 2004, a NASA probe named Stardust
, 240,000,000 miles from Earth, made a fly by of the Comet Wild 2, dipping into its geyser-like jets of ice particles and collecting a sample. The subsequent analysis of the samples startled and thrilled Astrobiologists, altered our model of planetary formation and evolution, and sobered and arrested the rest of the thinking world.
Although the mission went off without a hitch, this was no easy feat. Stardust first had to first align itself with the comet, which was seen to be flying through space at 60,000 mph, and, then, it had to make a dive through through the clouds of dust, nearing the icy center. Having completed this, it then had to endure the heavy bombardment of icy material inflicted on it by geysers shooting up at supersonic velocities (almost 14,000 miles per hour, roughly 6x the speed of a speeding bullet). Surviving this intact, it flew through the clouds of material and 'scooped' up samples with its "flypaper-like" aerogel collection grid, returning home on January 15th, 2006. With this being the first time a comet's interior had been sampled in its natural habitat, scientists the world over waited in anticipation as to what the samples contained. After three years of analysis the team studying the samples made an disturbing but remarkable discovery, in the dust from the comet, traces of an amino acid called glycine were found.
This may seem rather mundane until the realization that this molecule is an integral part of living things and that comets are fairly common in our Solar System and throughout galaxies. Glycine is one of the most common amino acids, and amino acids are, of course, the building blocks of proteins and are, obviously, essential for life. This discovery supports and furthers the idea that some of life's ingredients were delivered to Earth by meteorite and comet impacts long ago and implies that the fundamental building blocks of life could be prevalent in the universe (the odds of us finding this amino acid on our first sample of a comet in space being astronomical, excuse the pun). and strengthens the argument that life in the universe may be more common than rare. But where could these vital comets have come from, and how could they be delivered to Earth?
The proposed idea is that comets orbiting in the Kuiper belt in a chaotic fashion were dejected after a collision around 3.9 billion years ago in the early stages of the solar system by a planet like Uranus or Neptune. After gaining momentum and "our" desired trajectory, they were sent hurtling towards the proto-Earth to deliver the building blocks for life, the period known as the Late Heavy Bombardment. During this period it is thought that every square inch of Earth was impacted by a mixture of meteorites and comets.
Comets: not only are they a beautiful phenomena, leaving hundreds and thousands of miles long streams of material in a tail like fashion (due to the strains brought on by solar winds that can be viewed with a telescope and an acute knowledge of their whereabouts), but they also may be the facilitators of life. Earth, other planets and moons in our Solar System and beyond could have the rudimentary building blocks for life, thanks to these wonderful astral objects.