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Title: Probing the Rock Mass Fraction and Transport Efficiency inside Uranus Using 40 Ar Measurements
Abstract The bulk of Uranus consists of a rock–ice core, but the relative proportions of rock and ice are unknown. Radioactive decay of potassium in the silicates produces40Ar. If transport of argon from the core to the gaseous envelope is efficient, a measurement of40Ar in the envelope will provide a direct constraint on the rock mass present (assuming a chondritic rock composition). The expected40Ar concentrations in this case would be readily detectable by a mass spectrometer carried by a future atmospheric probe. For a given envelope concentration there is a trade-off between the rock mass present and the transport efficiency; this degeneracy could be overcome by making independent determinations of the rock mass (e.g., by gravity and seismology). Primordial40Ar is a potential confounding factor, especially if Ar/H2is significantly enhanced above solar or if degassing of radiogenic40Ar were inefficient. Unfortunately, the primordial40Ar/36Ar ratio is very uncertain; better constraints on this ratio through measurement or theory would be very helpful. Pollution of the envelope by silicates is another confounding factor but can be overcome by a measurement of the alkali metals in the envelope.  more » « less
Award ID(s):
2223935
PAR ID:
10535908
Author(s) / Creator(s):
; ; ;
Publisher / Repository:
American Astronomical Society
Date Published:
Journal Name:
The Planetary Science Journal
Volume:
5
Issue:
5
ISSN:
2632-3338
Page Range / eLocation ID:
109
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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