Lunar and Planetary Science XXXI 1383.pdf
Origin of the Moon and Halilean Jupiter’s Satellites Marakushev A.A. The Moon had its volcanic activity in the period of 4.6–3.2 Ga, and on Io, its analogy in the Jupiter’s system, volcanism continues now. Nevertheless, in spite of the age difference, the Moon regularly follows the row of Halilean Jupiter’s satellites by density (g/cm3) and unitless characteristic of the inner structure of satellites (Anderson et al., 1995; in parentheses): Io 3.53 (0.38) – the Moon 3.34 (0.39) – Europe 3.03 (0.34) – Ganymede 1.94 (0.31) – Callisto 1.8. The row of Halilean satellites is in the same regular correlation with the iron– silicate molten Jupiter’s core like the Moon with the Earth (figure). This correspondence was acquired on the stage of the Earth formation as a heavy molten core of the giant Protoearth surrounded by a satellite system in which the Moon occupied the same position as Io in the Jupiter’s system (Marakushev, 1999). After a loss of the fluid envelope, iron–silicate core of the Protoearth turned into a planet in its own right (Earth). As this took place, the satellite system of the Protoearth was also lost, and only the Moon retained. The analogy of the Moon with Halilean satellites reflects a giant size of the Protoearth and its comparison with Jupiter, because planets with moderate fluid envelopes (Saturn, Uranus, Neptune) were able to give rise only to light satellites with a density of less than 1.9 g/cm3. The formation of satellites was accompanied by an isolation of heavy cores of planets producing a quick rotation of their fluid envelopes (direct and reverse) and centrifugal forces. This was stimulated by liquid immiscibility.
Judging by the density of separated satellites, essentially aqueous dense phases (H2–
H2O) were separated and the outer icy satellites of group I with a reversed motion by orbits were formed at first (figure). Stabilization of normal rotation of Jupiter and separation of much dense satellites (II–III) reaching maximum values of its density (3.53 g/cm3) took place with the weightening of the core of the planet. Transition to the modern state resulted in the deceleration of rotation of Jupiter’s fluid envelope, and because of this, Jupiter could give rise only to light near-planetary satellites of group IV (figure) accompanied by the formation of a ring system. Lunar and Planetary Science XXXI 1383.pdf
ORIGIN OF MOON AND HALILEAN JUPITER'S SATELLITES: A. A Marakushev
Being separated from giant planetary envelopes as fluid–silicate molten mass, satellites are layered and consolidated from the periphery. This is accompanied by the increase of fluid pressure in their cores and leads to the development of their endogenic activity or explosive destruction giving rise to planetocentric meteorites.
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Figure. Diagram of distribution of density of the Moon and Jupiter’s satellites versus their distance from parent planets. 1 – Earth (density is recalculated for a pressure of zero); 2 – Moon; 3–20 – Jupiter (3), its iron–silicate molten core (4), and satellites (5 – Io, 6 – Europe, 7 – Ganymede, 8 – Callisto, 9 – Leda, 10 – Gimalia, 11 – Lisitea, 12 – Elara, 13 – Ananke, 14 – Karme, 15 – Pacife, 16 – Sinope, 17 – Adrastea, 18 – Metida, 19 – Teba, 20 – Amaltea. The direction of the Jupiter’s satellites rotation is indicated on the scheme of their orbits by arrows. I–IV – groups of satellites in the supposed sequence of their formation: I–II – distant satellites with reversed (I) and normal (II) rotation by orbits; III–IV – near-planetary massive satellites (III) and satellites of a low density surrounding the ring systems of planets (IV).