What Meteorites Brought With Them

As well as bringing heavy metals to Earth, asteroids and meteorites may have brought something even more valuable – the building blocks of life. The origin of life on Earth is a huge mystery, and its most basic components are the amino acids that go into building proteins, which build up into RNA that in turn builds up into DNA. Stanley Miller and Harold Urey famously showed that a soup of organic compounds, energised by lightning, could create amino acids, but there is also evidence that meteorites could also have brought large quantities of amino acids to Earth. In 2008, scientists at the Carnegie Institution in Washington DC found that two CR chondrites picked up in Antarctica in the 1990s contained higher concentrations of amino acids than had ever been seen in meteorites before. They contained 180 and 249 parts per million, compared to the typical 15 parts per million or less that most meteorites contain.

The amino acids could have formed within the parent body before it broke up. This suggests that chemical precursors such as ammonia that wound up in asteroids could have interacted with water, creating these amino acids. These fragments could have then rained down on Earth. These same precursors are likely to have been present in other primitive bodies such as comets, which were also raining material into the early Earth.