Hi again

Here's a link to an article from DAWN about the thermal modelling of Ceres...

Dawn's Early Light Vol2, issue 2

...there's also geophysical data consistent with Ceres having a rocky core and ice crust in abstract here...

P31C MCC:2008 Wednesday 0800h

New Developments in Planet Formation and Early

Solar System History I

Presiding:D Stevenson, California Institute of

Technology; A Halliday, ETH Zurich

P31C-01 08:00h

Ceres Observations with HST: Size, Shape, Pole

and Rocky Core

* Parker, J (joel@boulder.swri.edu) ,

Southwest Research Institute, Dept. of Space

Studies 1050 Walnut St., Boulder, CO 80302

United States
Thomas, P C

(thomas@baritone.astro.cornell.edu) , Cornell

University, 422 Space Sciences Bldg., Ithaca,

NY 14853-6801 United States
Young, E F (efy@boulder.swri.edu) , Southwest

Research Institute, Dept. of Space Studies

1050 Walnut St., Boulder, CO 80302 United

States
Sykes, M V (sykes@as.arizona.edu) , Planetary

Science Institute, 1700 E. Fort Lowell, Ste.

106, Tucson, AZ 85719-2395 United States
McFadden, L (mcfadden@astro.umd.edu) ,

University of Maryland, Depot. of Astronomy,

College Park, MD 20742 United States
Russell, C T (ctrussell@igpp.ucla.edu) ,

University of California Los Angeles,

Institute of Geophysics and Planetary Physics,

405 Hilgard Ave., Los Angeles, CA 90095-1567

United States
Stern, S A (astern@swri.edu) , Southwest

Research Institute, Dept. of Space Studies

1050 Walnut St., Boulder, CO 80302 United

States

Our team has obtained 259 images of Ceres

using the High Resolution Channel of the

Advanced Camera for Surveys on the Hubble

Space Telescope. These images were obtained at

high temporal sampling in three filter bands

(V, U, and Mid-UV) over the entire rotational

phase of Ceres. The resolution was 30

km/pixel, allowing us to detect and follow the

motions of surface features on Ceres for the

first time. Light and dark patches are seen on

the surface, with high contrast and

differences among the three filters. A strong

feature near the equator provided a control

point to definitively determine the rotational

pole of Ceres: RA=291 deg and Dec=59 deg.

Based on limb fits to an accuracy of nearly

0.1 pixel, our shape measurements show that

Ceres is rotationally symmetric with an

equatorial radius of 487.3 km and a polar

radius of 454.7 km with roughly 5 km

uncertainties. This flattening is

significantly less than expected for a relaxed

body of Ceres' mean density and rotation

period, but it is consistent with such a body

if Ceres has a central rocky core surrounded

by water ice. Support for this project is

through STScI grant HST-GO-09748.

...very interesting indeed. Ceres will be quite a high-light of the DAWN mission.

Adam