Using comets as vehiclesFrom the Journal of the British Interplanetary Society 1997, 50, 93-102. Michael N. Mautner
It may be possible to grow the necessary large amounts of microorganisms directly in carbonaceous asteroids or comets, and thereby use the comets themselves as vehicles.
Carbonaceous C1 meteorites, and presumably asteroids, contain water in about the biological ratio of 5:1 H2O/C, and N in the biological ratio of 10:1 C/N, as well as biologically usable forms of the other macronutrients S, P, Ca, Mg, Na and K in at least the biological C/X elemental ratios . Once the nutrient components are extracted, the residual inorganic components may be used for shielding materials for the microbial capsules.
As a possible method for converting comets to biomass, the loose icy, cometary matrix may be fragmented and enclosed in membranes in 1 kg spheres. Warming and melting such a unit, from 10 to 300 K, requires 5.1E9J, which can be provided by the solar energy flux of 325 W per m2 at 2 au, incident on the 3.1 m2 cross-section of a 1 m radius object during a two-months perihelion transit about 2 au. The microbial experiments show that in 6 - 8 days after inoculation, this organic solution will yield microbial densities of >1E8CFU/ml which can survive for several months [18, 19]. Subsequently, the microbial solution can be converted to 1 mm "hailstones". These microbial ice capsules can be accelerated out of the solar system, for example, by first accelerating the comets sunward into parabolic orbits, and in this manner dispersing the Oort cloud at the rate of 20 comets per year during 5E9 yr. This rate is comparable to the natural rate of 3 new comets/yr plus up to 1E9 new comets per/year during cometary showers , and the task may be accomplished at the required rate by processing every new comet that arives naturally from the Oort cloud.
An interesting experiment in this direction would be to inoculate the sub-crust zone of an inbound comet, and of enclosed samples of the cometary material embedded in the comet, the latter to allow melting near the perihelion without evaporation. Embedded sensors could monitor microbial growth during the perihelion passage and, for a short-period comets, during further passages, to verify microbial growth in cometary materials and environments. Laboratory microbiology experiments with returned cometary materials would be also of interest.
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