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 some of them are.
For this experiment, the team tested the theory that amino acids were first made in interstellar molecular clouds and then landed on Earth in an asteroid. 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 submerged the residue in her 50- and 125-degree water for various 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 remained constant before and after the chunks were put into the asteroid simulation. There was always more glycine than serine and more serine than alanine.
According to Qasim, the trend is worth noting. This is because it indicates that the conditions within the interstellar cloud strongly influenced the composition of amino acids within the asteroid. Ultimately, however, their experiments faced the same problem as other laboratory studies: the amino acid distributions did not match those found in real meteorites. There was an excess of beta-alanine over alpha-alanine in laboratory samples. I didn’t find it.
This is probably because their recipe is 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 a pristine sample as a starting point. This September, NASA’s OSIRIS-REx mission will bring back what looks like her 200-gram chunk of asteroid Bennu. (This is 40 times larger than the last sample of pristine space rock we got.) A quarter of the samples are analyzed for amino acids. It can also reveal other fragile substances present on the asteroid, but they cannot survive the journey to Earth without the protection of the spaceship. help.
