[FPSPACE] Titan at the time of the Cassini spacecraft first flyby: a prediction for its or

[LARRY KLAES]

Astrophysics, abstract
astro-ph/0602512

From: Andrew Prentice [view email]

Date (v1): Thu, 23 Feb 2006 11:04:48 GMT (262kb)
Date (revised v2): Fri, 24 Feb 2006 00:56:14 GMT (262kb)

Titan at the time of the Cassini spacecraft first flyby: a prediction for 
its origin, bulk chemical composition and internal physical structure

Authors: A.J.R. Prentice

Comments: This paper was submitted to the MNRAS on 27 October 2004 to 
coincide with the Cassini spacecraft first flyby of Titan. It was assigned 
the ref. no. ME1249 but was not published.

It is proposed that Titan condensed in a solar orbit, prior to capture by 
Saturn. Hyperion is the remnant of a Rhea-sized native moon of Saturn that 
was destroyed by impact with Titan. The Titanian surface should be mostly 
smooth and crater-free. Titan is predicted to be a 2-zone satellite with a 
rock-graphite core and water ice mantle. New calculations completed since 
ME1249 yield an axial moment-of-inertia coefficient C/MR^2 = 0.317 +/- 
0.004.

This prediction is to be tested during the first dedicated radio science 
flypast of Titan on 27 February 2006. Cassini should discover mass anomalies 
in the upper mantle of Titan that correspond with the burial sites of ~ 2 
former native moons of Saturn

I report the results of a new set of calculations for the gravitational 
contraction of the proto-solar cloud to quantify the idea that Titan may be 
a captured moon of Saturn (Prentice 1981, 1984).

It is proposed that Titan initially condensed as a secondary embryo in the 
same proto-solar gas ring from which the central solid core and gaseous 
envelope of Saturn were acquired. At the orbit of Saturn, the bulk chemical 
constituents of the condensate are rock (mass fraction 0.494), water ice 
(0.474), and graphite (0.032). The mean density is 1523 kg/m^3. Structural 
models for a frozen Titan yield a mean density of 2095 kg/m^3 (chemically 
homogeneous case) and 1904 kg/m^3 (fully differentiated 2-zone case). The 
agreement to one percent of the latter value with the observed mean density 
suggests that Titan is indeed a fully differentiated satellite. The value of 
C/MR^2 for this model is 0.316.

It is predicted that Titan has no internal ocean or induced magnetic field 
but it may possess a small native dipole field of magnitude 2 x 10^11 Tesla 
m^3 due to thermoremanent magnetization fed by the ancient magnetic field of 
Saturn.

Capture of Titan was achieved by gas drag at the edge of the proto-Saturnian 
envelope at a time when that cloud had a radius close to the present orbital 
size of Titan. Collisional drag was also probably an important agent in 
securing the capture of Titan.

Perhaps Hyperion is the shattered remnant of a pre-existing native moon of 
Saturn that was destroyed on the arrival of Titan. Titan should thus have 
much the same appearance as Triton, being nearly smooth, crater-free and 
streaked with elemental carbon (Prentice 2004a).

http://arxiv.org/abs/astro-ph/0602512