You have probably seen the photos of alleged fossil microorganisms in meteorites, but these are unconvincing. Look hard enough, and you will find faces in rocks. Lots of people have found supposed fossil microorganisms that turned out to be random shapes in rocks.
More impressive are asymmetric amino acids. The meteorite Ivuna Cl1 contained 372 parts per billion of l glutamic acid, but only 8 parts per billion of d glutamic acid, indicating that that glutamic acid came from living things. That there was glutamic acid but no leucine indicates that those living things died millions or billions of years ago, hence unlikely to be the product of earthly contamination of the meteorite. Seeming fossils by themselves would not be impressive. Finding traces of biological amino acids with what look like fossilized earthly microorganisms is a pretty good indication that these are indeed real fossils – in which case the most primitive forms of life on earth probably arrived from elsewhere.
Er… who are you? Are you an academic, astronaut, collector, vendor, interested guy (and undoubtedly interesting as well) or what?
Am writing a book and need to know to whom I am listening…
Mud. They are similar to what you would get if scooped out some mud from the marsh of a river delta, and let it dry, or got some muddy water from a slow flowing river, and let it dry. They are in substantial part composed of clay, which forms when rock is exposed to water for vast periods. So the material of which they are composed was wet, and was wet for vast ages, not just briefly.
The paper suggests that they were formed in ancient cryovolcanoes – volcanoes that erupt warm muddy water into cold vacuum, rather than lava.
Curious as to the origins of the Cl1 meteorites……