Galilean Satellites as Sites for Incipient Life, and the Earth as its Shelter

It appears fairly obvious that life could evolve only in the presence of water. However, from the outset the Earth and Mars had very little water (~0.03%) and protoorganic substances (several orders of magnitude less than that), which poses two problems, namely, (1) a concentration gap, where a reasonable original concentration of aminoacids in water could not be higher than ∼10 kg/l, which made their fusion to more complex formations unlikely, and (2) inhibition of this fusion by salts like NaCl, MgSO4 etc., whose high concentration is due to their being washed out of rocks by small amounts of water. An opposite situation occurred on the Galilean satellites, where water constituted ∼50%, hydrocarbons ∼5-10%, and the nitrate-based organics ∼1% (the estimates are based on the composition of cometary nuclei). Liquid water containing only minute amounts of salts could exist here both after the satellite accretion and during hundreds of Myrs following regular global explosions of the icy envelope saturated by 2H2+O2, i.e., the products of volumetric electrolysis of these ices due to the action of the electric currents excited by the strong (~10 Gauss) ancient magnetic field of Jupiter. On Io, two to three such explosions occurred altogether, on Europa, two, and on Ganymede, only one. The ices of Callisto did not explode. It appears that Titan also suffered an explosion, only ∼10 kyr ago, a conjecture corroborated by the fact that many of our predictions have obtained observational support. An explosion ejects numerous fragments of the outer icy-envelope layers, likewise saturated by organics and electrolysis products. These are the nuclei of the SP comets, whose behavior and chemical manifestations are accounted for by such a composition. An explosion creates on the satellites a deep (700-800 km) hot ocean of a gradually cooling almost fresh water. Part of the pyrolized organics ascends to the surface, while the other, the heavier one, settles down to the bottom. Some of the ice fragments of the primary composition ejected in an explosion continue to fall into the ocean during a long time, including the period after its cooling and formation of ice on its surface. In these conditions, the problems of salt excess or a concentration gap simply do not exist (the concentration of organic substances near the surface of the ocean and on its bottom may reach as high as 100%). The thermodynamic parameters of volatiles vary in the ranges inconceivable for the Earth, namely, T ∼ 10−10 K, p ∼ 0−10 atm, with the pristine and highly pyrolized components being in direct contact. Powerful energy flows, including the electrical ones, accompanied by intensive convection motions set in. One may conjecture the formation of a rich variety of catalytic substances. Absolute enantiomeric synthesis could take place in electrolysis in the presence of a magnetic field. Subsequent explosions of icy envelopes make the conditions still more diverse. It thus appears that the probability of synthesis of biological compounds here is much higher than that on the Earth. The Earth, because of its milder conditions, could provide an ideal habitat for development of the ready-to-evolve primitive life forms. It thus becomes clear that the assumption of ejection of cometary nuclei from icy moon-like bodies removes the problem of transfer of the life borne on them to the Earth. Interestingly, the multiplicity of envelope explosions on Io and Europa, where, thus, protobiological objects could form and evolve in repeatedly occurring extremal conditions, may shed light on the nature of intermittent stages of the development of biota on the Earth, of the type of the pre-Cambrian extinction followed by subsequent explosive growth of life in a new direction etc.