A common mass scaling for satellite systems of gaseous planets Options

[Guest_AlexBlackwell_*]

Canup and Ward have a new, interesting paper ("A common mass scaling for satellite systems of gaseous planets") in the June 15, 2006, issue of Nature. See the Editor's Summary for more details.

[Rob Pinnegar]

This is an interesting point, especially when comparing the relative sizes of the major satellites in the Jovian and Uranian systems: two good-sized ones closer in, two somewhat bigger ones further out. (Saturn's system, in a way, is a hybrid: it resembles Uranus' with a Galilean thrown in for good measure).

Is Neptune omited from this argument (even though Triton roughly follows the pattern)?

[Guest_AlexBlackwell_*]

Is Neptune omited from this argument (even though Triton roughly follows the pattern)?

Primarily, Canup and Ward use Jupiter, Saturn, and Uranus and their coterie of satellites in their model, though they do consider Neptune. From the paper (references omitted):

"Although the model presented here applies to regular satellite formation, it is remarkable that Neptune's single large, irregular satellite, Triton, also contains a similar mass fraction, with M(Triton)/M(P) ~ 2.1 x 10^-4. Triton's orbit is retrograde and inclined, and it is believed to have been captured intact from heliocentric orbit. Although we lack direct evidence of a putative original prograde neptunian satellite system, it seems clear that it cannot have contained much greater total mass than Triton itself. Otherwise, a retrograde and initially eccentric Triton would have been destroyed while traversing the regular satellite region (either as it was accreted or collisionally disrupted, or by the decay of its orbital angular momentum36 owing to interactions with a much greater mass in prograde material). The survival of a captured retrograde satellite requires it to have comparable or greater mass than any prograde system with which it actively interacts. As larger interlopers would have been less numerous (and therefore captured less frequently), the most probable surviving Triton-like object would be one having the smallest mass affording its survival, which would suggest that M(Triton) is similar to the total mass of Neptune's original regular satellites, or M(T)/M(Neptune) ~ O(10^-4) as well."