Bacterial morphologies in carbonaceous meteorites and comet dust

Abstract

Three decades ago the first convincing evidence of microbial fossils in carbonaceous chondrites was discovered and reported by Hans Dieter Pflug and his collaborators. In addition to morphology, other data, notably laser mass spectroscopy, confirmed the identification of such structures as putative bacterial fossils. Balloon-borne cryosampling of the stratosphere enables recovery of fragile cometary dust aggregates with their structure and carbonaceous matter largely intact. SEM studies of texture and morphology of particles in the Cardiff collection, together with EDX identifications, show two main types of putative bio-fossils -firstly organic-walled hollow spheres around 10μm across, secondly siliceous diatom skeletons similar to those found in carbonaceous chondrites and terrestrial sedimentary rocks and termed 'acritarchs'. Since carbonaceous chondrites (particularly Type 1 chondrites) are thought to be extinct comets the data reviewed in this article provide strong support for theories of cometary panspermia.

The origin of life from primordial planets

“…15 shows a sample of microbial fossils in meteorites and comet dust. Biochemical markers corroborate the putative biological identification of these structures (Wickramasinghe et al 2010a, b). Moreover, recent studies indicate that life forms on Earth have made only a modest progress towards achieving the biochemical diversity displayed within the Murchison meteorite, even with the continuing injection of cometary organics and presumably cometary life (Schmitt-Kopplan et al 2010).…”

“…The onset of prebiotic chemistry and the emergence of life templates as a culmination of such a process must await the condensation of water molecules and organics first into solid grains and thence into planetary cores (Wickramasinghe et al 2010 a ). Assuming the collapsing proto-planet cloud keeps track with the background radiation temperature, this can be shown to happen between ~2–30 My after the plasma to neutral transition.…”