can vesta have a polar cap? eleonora ammannito inaf/ifsi - roma cisas - padova cisas-upd
TRANSCRIPT
Can Vesta have a polar cap?Can Vesta have a polar cap?
Eleonora AmmannitoINAF/IFSI - Roma
CISAS - Padova
CISAS-UPD
The modelThe model
• Time-dependent, unidimensional partial differential equations, expressing the conservation of energy (heat diffusion) and mass (gas diffusion), in the general form
= density, = flux, Q = source term• PDE's are solved numerically in
discrete time steps on a discrete grid
Qt
The initial conditionsThe initial conditions
70
90
110
130
150
170
190
210
-4 -3 -2 -1 0 1 2 3 4
orbital position
tem
pera
ture
(k)
10 20 30 40 50 60 65 70 75 80 85
semi major axis (a) 2.362 (AU)eccentricity (e) 0.089rotational period (p) 5.342 (h)latitude (theta) 90 ÷ 75 (deg)obliquity* (q) 21.8 (deg)Perihelion argument (w ) 150.27 (deg)
Seasonal variation of the temperature at different latitudes on the surface of Vesta. It was condidered the equilibrium between the solar irradiance at the Vesta’s distance from the Sun at each latitude and the thermal emission of the body.
albedo (al) 0.04IR emissivity (em) 0.9porosity (po) 0.3radius (r) 265 (km)dust thermal conduct. 0.25 ÷ 1.0 (W/(m*K))dust specific heat 1200 ÷ 1300 (J/(Kg*K))n° layers 100thikness of layers 0.001 (m)
Parametri orbitali:
Parametri fisici:
Preliminary indicationsPreliminary indications
-0.15
-0.13
-0.11
-0.09
-0.07
-0.05
-0.03
-0.01
0 100 200 300 400 500 600 700 800 900 1000
vesta's orbits
Po
siti
on
of
the
ice
wrt
th
e su
rfac
e (m
)
90 85 80