Panspermia: |
Directed Panspermia
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Introduction
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In the previous papers [4-6], we considered solar sail missions of a few vehicles targeted at specific nearby planetary systems that possess protoplanetary dust rings, such as Vega, beta Pictoris, and Fomalhout. For such missions, suitable targets should be within <100 ly for targeting accuracy, and have observable accretion disks or planets, preferably about young F, G or K type stars that will stay on the main sequence for >1E9 years to allow higher evolution. Only a few suitable objects are known. It may be more efficient therefore to aim for nearby star-forming regions with large concentrations of accreting planetary systems. Such regions are found in collapsing dense molecular clouds that fragment to form stellar associations, some with up to 100 new 0.5 - 5 M¤ , long-lived stars. The nearest suitable star-forming zones are dense regions (>106 cm-3), that are >100 ly away. It is not possible to target a few vehicles accurately at individual stars at such distances, and even if targeted, the vehicles may be scattered by the high density medium. For such environments, a statistical swarm strategy may be preferred. The swarm strategy uses solar sails to launch large numbers of small, milligram size, microbial packets. The size of the packets is designed so that they transit the thinner cloud regions and are captured in high-density protostellar condensations, where they will fragment into small, eg., 30 m m radius capsules. Some capsules will land on already accreted planets, while other capsules that arrive in actively accreting protoplanetary systems, will be captured in asteroids and comets. Subsequently, when host comets warm up near perihelion passages, the microbial payload in them may multiply [17]; in any event, microbes or capsules will be ejected with the cometary dust particles and like them, a fraction will be captured by planets. Alternatively, the capsules can be transported to planets when the host asteroids and comets, or their meteorite fragments, impact. Using nutrients provided in the capsule, supplemented by the rich nutrients in the host carbonaceous meteorite or cometary matrix [18,19], and subject to wet and warm planetary conditions, the microbial payload can then start to multiply. Materials from the planet will mix with the capsule and meteorite microenvironments, and the micoorganisms can adapt gradually to the planetary chemistry. Finally, the microorganisms will break free to multiply and evolve in the environment of the new planet. This sequence will be evaluated below quantitatively, to estimate the probability of success and the required amounts of panspermia material. |
