Nearly 100 different types of amino acids have been observed in meteorites, but only 12 of the 20 essential to life have been discovered. I have. Although they all have a “left-handed” structure, abiotic processes create left-handed and right-handed molecules equally. Dworkin says it does.
For this experiment, the team tested the theory that amino acids were first created within interstellar molecular clouds and then transported to Earth within asteroids. They decided to recreate the conditions these molecules would have been exposed to at each stage of their journey. If this process produced the same types of amino acids in the same proportions as those found in recovered meteorites, it would help test the theory.
The researchers first created the most common molecular ices (water, carbon dioxide, methanol, and ammonia) found in interstellar clouds in a vacuum chamber. They then bombarded the ice with beams of high-energy protons, mimicking collisions with cosmic rays in deep space. The ice broke apart and reassembled into larger molecules, eventually forming macroscopic cancer-like residues — clumps of amino acids.
Next, we simulated the interior of an asteroid. Asteroids contain liquid water and can be surprisingly hot, between 50 and 300 degrees Celsius. They soaked the residue in her 50- and 125-degree water for varying times. This increased levels of some amino acids but not others. For example, the amount of glycine and serine both doubled. Alanine content remained the same. However, their relative levels were consistent before and after chunks were put into asteroid simulations. There was always more glycine than serine, and there was always more serine than alanine.
According to Qasim, the trend is worth noting. This is because it indicates that the conditions in the interstellar cloud strongly influenced the composition of amino acids in the asteroid. Ultimately, however, their experiments ran into the same problem as other laboratory studies: the distribution of amino acids did not match those found in real meteorites. (In meteorites, this usually happens the other way around.) If there was a recipe for creating a precursor to life, they would find it. It was not.
This is probably because their recipe was too simple, Kassim says.
But there is another possibility. The meteorite samples they’ve been using for comparison may be contaminated. When meteorites crash-landed, they may have been altered by their interaction with the Earth’s atmosphere and biology, altered by centuries of geological activity that melted, subducted, and reclaimed the planet’s surface. You may have
One way to test this is to use the original sample as a starting point. This September, NASA’s OSIRIS-REx mission will bring home something like 200 grams. Blob of asteroid Bennu. (this is, Last sample of pristine space rock.) A quarter of the sample will be analyzed for amino acids to help pinpoint the cause of the discrepancies between laboratory studies and the meteorite. We can make it clear, but we can’t survive a trip to our planet without the protection of a spaceship.
