'The seed of life' on Earth brought by meteors

Back in time 3 or 4 billion years ago, Earth was a dry, hot and lifeless place. All are quiet. Unexpectedly, a meteorite crashed down a desert desert with a speed of over 10,000 miles per hour. This terrible collision may have planted the life germ on Earth.

In a report at the 235th National Meeting of the American Chemical Community (ACS), Dr. Ronald Breslow, Lecturer at Columbia University and former ACS President, described how amino acid was described. from the universe.

The chains of amino acids make up proteins in humans, plants and other life forms on Earth. There are two directions of amino acids, left and right, opposite each other like objects and reflections in the mirror, or like the left and right hands. This is called 'hand symmetry'. The protein must contain one of two symmetrical forms of amino acid, left or right, then life forms.

'If you reverse the symmetry, the properties of a protein will change a lot. Life cannot exist if it is based on the chaotic arrangement of this material. '

The left - handed amino acid 'L-amino acid' predominates on Earth, with only a few exceptions of right-handed amino acid-based bacteria. The chemistry professor at Columbia University said that a collision with a meteorite brought amino acids to Earth, especially the left-handed protein units.

A sapphire model (the white and purple units sold) is processing an amino acid (green). (Photo: Courtesy Los Alamos National Laboratory)

'These meteorites bring what I call the' seed of hand symmetry '. If a universe is a mirror image of the universe we know, I believe it will have right-handed amino acids. That's why I still half jokingly said that there is someone on the other side of the universe whose heart is on the right. '

These amino acid "seeds" form in the space between planets, probably on small planets as they dive in the air. Initially, they have equal amounts of left and right amino acids. But when these rocks rush through neutron stars, the rays of stars destroy selectively an amino acid. These stars emit light that is polarized in a circular way - in one direction, its light is distributed to the right. Turning 180 degrees to the other side, the star emits left polarized light.

All meteorites that fall to Earth suffer from one of these two polarized light rays. Breslow said previous experiments confirmed that circularly polarized light selectively destroys a symmetrical type of amino acid . The result is an excess of 5-10% in L-amino acid form, ie left-handed amino acid. Evidence of this left-handed amino acid lies on the surface of these meteorites, even when they hit Earth in the last 100 years in Australia and Tennessee (USA).

Breslow simulated what happened after the dust of the impact slumped, when the amino acid on the meteor melted into the primitive water. Under these 'wonderful pre-life conditions' - high temperatures like the desert and some water - he introduced the amino acid chemical precursor to the amino acids found on celestial bodies.

Breslow and Columbia University graduate student Mindy Levine discovered cosmic amino acids that could directly convert hand symmetry into a single amino acid form in current organisms. So far, Breslow's team is the first to demonstrate that this switch can occur under these conditions.

On Earth before life formed, this conversion left an excess of left-handed amino acids. His next experiment was to recreate the chemical that led to a rapid and final increase in the dominance of left-handed amino acids. He started with a 5% excess of a form of amino acid in water and dissolved it.

Breslow found that both left and right-handed amino acids will work together when they crystallize from the water. The left hand acid amino separated from the solvent when the water evaporated, causing the left hand amino acid content in the solvent to increase. Finally, excess amino acids become popular because they are used by selected living organisms.

Other assumptions have been made to explain the dominance of L-amino acid. For example, an assumption that polarized light of neutron stars has reached Earth and directly destroys right-handed amino acids. According to Breslow 'But the evidence clearly shows that these materials are being formed in space and reach Earth thanks to meteorites.'

The next steps leading to the formation of life are still mysterious. Breslow hopes to learn about the Earth before forming life when shifting his interest to hydrochloric acid, the chemical unit of DNA and a more primitive relative of RNA.

'This work relates to the possibility that life exists somewhere (extraterrestrial). Everything that's happening on Earth comes from meteorites accidentally landing here. They certainly fell to other places too. If there is a planet with water and all the conditions required for life, we will have a similar process going on. '