30 research outputs found
The Location of the Snow Line in Protostellar Disks
The snow line in a gas disk is defined as the distance from the star beyond
which the water ice is stable against evaporation. Since oxygen is the most
abundant element after hydrogen and helium, the presence of ice grains can have
important consequences for disk evolution. However, determining the position of
the snow line is not simple. I discuss some of the important processes that
affect the position of the snow line.Comment: 8 pages, 5 figures. Invited talk at IAU Symposium 263 - Icy Bodies in
the Solar System. Rio de Janeiro, Aug. 200
Interior Models of Uranus and Neptune
'Empirical' models (pressure vs. density) of Uranus and Neptune interiors
constrained by the gravitational coefficients J_2, J_4, the planetary radii and
masses, and Voyager solid-body rotation periods are presented. The empirical
pressure-density profiles are then interpreted in terms of physical equations
of state of hydrogen, helium, ice (H_2O), and rock (SiO_2) to test the physical
plausibility of the models. The compositions of Uranus and Neptune are found to
be similar with somewhat different distributions of the high-Z material. The
big difference between the two planets is that Neptune requires a non-solar
envelope while Uranus is best matched with a solar composition envelope. Our
analysis suggests that the heavier elements in both Uranus' and Neptune's
interior might increase gradually towards the planetary centers. Indeed it is
possible to fit the gravitational moments without sharp compositional
transitions.Comment: 16 pages, accepted for publication in Ap
A Simple Model for Understanding the DIM Dust Measurement at Comet 67P/Churyumov-Gerasimenko
We present a simple model for gas and dust flow from
67P/Churyumov-Gerasimenko that can be used to understand the grain impact
observed by the DIM instrument on Philae (Krueger et al. 2015) We show how
model results when applied to the GIADA measurements (Rotundi et al. 2015;
Della Corte et al. 2015) can be used, in conjunction with the results found by
the MIRO (Schloerb et al. 2015) and VIRTIS (De Sanctis et al. 2015) instruments
to infer surface properties such as surface temperature and surface ice
fraction.Comment: 15 pages, 4 figures. Accepted for publication in Planetary and Space
Scienc