Further to Will the shooting stars please rise? Rob Sheldon writes to say
Just to set the record straight. The meteorite they showed in the article, was not a piece of iron, it was a “framboid” from an extinct comet made up of Fe3O4 “magnetite”. The reason it looks all lumpy, is that it is a ball made up of ball bearings, each one small enough to be spontaneously magnetized. These ball bearings are not random crystallization of iron, rather they are biominerals, made by living organisms, and far from equilibrium. The closest analog is a Fe3S4 mineral “goethite” found in deep gold mines in South Africa. We don’t know much about the organisms that make them–they look to be bacteria–but why they need a sensitive magnetic compass we don’t know.
So the oxygen in the Fe3O4 framboid did not come from the Earth’s atmosphere, it came from space, along with the comet that carried it, more than 2.7 billion years ago, with a freightload of bacteria. More.
What do readers think? Was Earth’s life first begun in space?
See also: Paper: Jupiter doesn’t shield Earth, comets kickstarted life
Comets brought life to Europa’s oceans?
Origin of life (the skinny)
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