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Comment Re:Terrestrial origin? (Score 1) 103

I really don't see any reference in the article to consideration of the possibility that these meteors might be terrestrial in origin - blasted into space from Earth's crust by a large impactor, and eventually re-entering, to be discovered and found bearing remnants of terrestrial bacteria.

Nothing in the paper is inconsistent with that hypothesis. All of the attention in the article devoted to possible sources in comets, asteroids, Jovian moons, and the Kuiper Belt, but no consideration given to the closest source of organic materials - the earth itself.

Sounds like a severe case of confirmation bias...

The deuterium/hydrogen ratios are consistent with cometary origin

Comment CI1 chondrite meteorites in question (Score 1) 103

If there ever is a meteorite type likely to preserve extra-terrestrial life, it is the CI1 chondrites described in the article. They are micro-breccias thought to be regolith (in this case, material weathered by water) from the surface of the parent body – probably an asteroid or comet. These extremely rare meteorites crumble to dust when they get wet because their microscopic particles are held together with clay and water-soluble minerals. Only 5 falls have been directly observed, Orgueil in 1864 being the biggest (4 others were found in Antarctica). The CI1s are soft enough to be cut with a knife, and early observers described them as humus- or bitumen-like. They are highly carbonaceous and contain complex organic compounds such as kerogen, long-chain fatty acids, protein amino acids, and the breakdown products of chlorophyll. The microscopic filaments exposed on fresh surfaces look very much like bacteria and certainly are not biological contaminants because they lack nitrogen, as do multi-million year old fossils from Earth.

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