Meteorite/Planetary Science Quiz

Question #3

One of the theories for the origin of life on Earth is that organic molecules were deposited early in Earth's development by meteorites, comets, and interplanetary dust particles (IDP's). Of the three which is believed to have been the dominant source?

All three have been studied and currently there is no clear answer on this.

For almost 100 years it has been believed that a substantial amount of Earth's prebiotic store of organic molecules were delivered by comets and asteroids. This belief gained greater support after spacecraft missions to comet Halley revealed it to be about 25% organic by mass. Impact modeling studies however have suggested that most but not all organics would be destroyed in large comet and asteroid impacts.

The influx rate of meteorites does not seem sufficient to be the main source either.

In 1992, Chyba and Sagan concluded that dominant source of organics to Earth would have been IDP's which appear to be 10% organic by mass and, due to their small size, would decelerate gently into the atmosphere with their organics intact. However a more recent study has shown that IDP's would have been subjected to destructive temperatures of at least 1 second above 1,200C and about 6 seconds above 500C.

At the present time, all three of the likely delivery mechanisms - comets, meteorites, and IDP's - seem to result in low global concentrations of amino acids so their origins remain poorly understood.

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