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Home » Note, Paper: Icarus Incoming

Note, Paper: Icarus Incoming

Time again for Icarus, an explicitly Solar-System-centric journal, In the August (vol. 418) issue:

Engels, T. Monteux, J. Boyet, M. et al. Large impacts and their contribution to the water budget of the … a 116124 .2024.116124
Pravec, P. Meyer, A. J. Scheirich,P. et al. Rotational lightcurves of Dimorphos and constraints on its po… a 116138 .2024.116138
Oldani, V. Manzini, F. Ochner, P. et al. Comet 81P/Wild 2: Changes in the spin axis orientation during … a 116141 .2024.116141
Ikeya, R. Hirata, N. Gravitational disturbance on asteroidal ring systems by close encounter with a sma… a 116153 .2024.116153

And time again to deflate the Moon hype. Earth’s old satellite is exceedingly dry, as dry as Earth was when it was a ball of molten rock. The purported water is a) not high, compared to carbonaceous chondrite bodies; b) not from comets, but likely asteroids (including astero-comets… the carbonaceous asteroids); and c) less accessible than the accessible carbonaceous asteroids. Engels et al. describe the contrived circumstances in which an impact during the early Solar System could deliver part-per-million levels of water to the Moon (and actually have it stay, not vaporize back to space). These circumstances are… contrived. Hence, the part per million versus few parts per million water levels are stochastic; if you could rewind, and play back the history of the Solar System, lunar water would vanish and reappear for different rewind/replays, as chance events either happen, or don’t.

Pravec et al. do the more prosaic work of follow-up studies after the DART impact experiment. If the asteroid (Didymos) is a dot of light in even a large telescope, then its binary (Dimorphos) is, also, a smaller dot of light. Yet we can deduce the properties of Dimorphos, the DART subject, because we’re smart, and good at pulling information out of dots of light.

Briefly touching on a non-asteroid: Comet Wild 2 is well-studied, even though the nucleus is an obscured dot of light: when near Earth, the active small body is shrouded in a coma. Yet we can still speak of its properties, like spin rate and vector (the pointing of the spin axis).

And speaking of shrouded: asteroids (well… astero-comets, as these Centaurs are past Jupiter, hard to categorize) can have rings. Dynamically, we can study gravity as pure, direct, unambiguous math. What does that math tell us of ring behavior? Ask a dynamicist- one (or, here, two) that did the math.

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