“As Cassini’s extraordinary 13 years of exploration concludes, enjoy this up-to-the-minute, far-reaching, wide-ranging look at that little moon Enceladus, at Saturn with the big possibilities”, Carolyn C. Porco, University of California, Berkeley, California. Space Science Institute, Boulder, Colorado.
“The four following papers in this collection address, in one form or another, the anticipated bioloads at Enceladus, and the detectable biosignatures that might be present in its plume. Steel et al. (2017) construct a thermal model that assumes 10% of the geothermal heat emerging from the moon’s core drives hot (90°C) hydrothermal fluid flow, which results, through water/rock interactions, in the production of H2. In their work, 100% of the molecular hydrogen thus produced is subsequently consumed by methanogens to produce biomass. They thus estimate, at the vents, 90 μM of biologically produced amino acids, and microbial concentrations as high as 109 cells/mL; 10% of the latter rise in the thermal plumes that originate at the vents and eventually reach the base of the ice shell. If these authors are correct, and Enceladus approaches this high-efficiency scenario, especially if the process of bubble-scrubbing (see below) is at work, then the search for biosignatures, even microbes, in the samples collected from Enceladus’ plume could be easily accomplished.”
PS “Convergence to Panspermia”?