Life on Earth May Have Been Seeded by Comets
Image: Michael Karrer
One of the oldest questions on earth is how all this crazy life started. Where did you come from? How about your office plant, or your cat? For a long time, our only working idea was that gods from the heavens had provided the seed of life. We may, at least, have been looking into the correct direction: researchers at UC Berkeley recently added evidence to the idea that life on Earth came from a comet.
The idea goes like this: the so-called “building blocks of life” on this planet are called dipeptides. And the real mystery is where these dipeptides came from. The Berkeley scientists’ research suggests that dipeptides could have formed on interplanetary dust and been carried down to earth on a comet. Berkeley writes:
Chemists from the University of California, Berkeley, and the University of Hawaii, Manoa, showed that conditions in space are capable of creating complex dipeptides – linked pairs of amino acids – that are essential building blocks shared by all living things. The discovery opens the door to the possibility that these molecules were brought to Earth aboard a comet or possibly meteorites, catalyzing the formation of proteins (polypeptides), enzymes and even more complex molecules, such as sugars, that are necessary for life.
Or, in the paper itself, the authors put it this way:
Our results indicate that the radiation-induced, non-enzymatic formation of proteinogenic dipeptides in interstellar ice analogs is facile. Once synthesized and incorporated into the ”building material” of solar systems, biomolecules at least as complex as dipeptides could have been delivered to habitable planets such as early Earth by meteorites and comets, thus seeding the beginning of life as we know it.
They figured this out by making a mini-comet in the lab. Combining carbon dioxide, ammonia and other chemicals like methane at super cold temperatures (space is pretty cold), they created a tiny comet-like thing. Then they added the lab equivalent of cosmic rays, zapping the mini-comet with electrons. What they saw was that the combination of these high energy electrons and the comet they had built created organic molecules like amino acids and dipeptides.
The idea is that this reaction happened on its own in space, and those dipeptides were carried down to earth on that icy comet. In other words, the necessary blocks of life might really have descended to Earth from the sky.
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