February 04, 2013
While the origin of life remains mysterious, scientists are finding more and more evidence that material created in space and delivered to Earth by comet and meteor impacts could have given a boost to the start of life. Some meteorites supply molecules that can be used as building blocks to make certain kinds of larger molecules that are critical for life.
Researchers have analyzed carbon-rich meteorites (carbonaceous chondrites) and found amino acids, which are used to make proteins. Proteins are among the most important molecules in life, used to make structures like hair and skin, and to speed up or regulate chemical reactions. They have also found components used to make DNA, the molecule that carries the instructions for how to build and regulate a living organism, as well as other biologically important molecules like nitrogen heterocycles, sugar-related organic compounds, and compounds found in modern metabolism.
However, these carbon-rich meteorites are relatively rare, comprising less than five percent of recovered meteorites, and meteorites make up just a portion of the extraterrestrial material that comes to Earth. Also, the building-block molecules found in them usually have been at low concentrations, typically parts-per-million or parts-per-billion. This raises the question of how significant their supply of raw material was. However, Earth constantly receives other extraterrestrial material – mostly in the form of dust from comets and asteroids.
image credit: Michael Callahan