Was life on Earth started by an asteroid?

According to some versions of the theory of “panspermia”, meteorites are responsible for bringing the first primordial life to Earth.

Adapted from Wikimedia Commons file http://en.wikipedia.org/wiki/File:Meteor_Bolide.JPGThe theory holds that either very simple forms of life or the materials necessary for it to form are carried to Earth on comets or fragments of asteroids. These survive their journey through the atmosphere and ultimately evolve into the species we see around us today – including the very scientists hypothesising about their origins.

Certain amino acids – the “building blocks” of life, necessary to build proteins ­­– have been found by NASA on comets, and analysis of some meteorites has suggested that amino acids and other organic compounds may have formed in space, rather than being present as a result of contamination of the samples.

However it is difficult to test panspermia theories fully without exploring or surveying a huge amount of space. Critics point out that it is uncommon for the molecules required for life to develop are only rarely found together at sufficiently high densities for chemical reactions to occur.

Similarly, comet impacts have been credited as the source of Earth’s water.

Find out more about comets on physics.org

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