- 11 Mar '06 04:21Since all this news about Encaledus I was going over a data sheet

about Saturn and these three lines struck me as odd:

Gravity (eq., 1 bar) (m/s2) 10.44 9.80 1.065

Acceleration (eq., 1 bar) (m/s2) 8.96 9.78 0.916

Escape velocity (km/s) 35.5 11.19 3.172

The first figure is the gravity of Saturn, then earth then the ratio between the two. You see gravity and acceleration as nearly equal to earths but then you look at the escape velocity and you see Saturn has an escape velocity of three times that of earth. How can that be? - 11 Mar '06 05:55Well I let my rusty neurons grind on it for a while and came to the

conclusion the one bar figure must be the key. It must represent

the gravity at the depth in Saturn's atmosphere that is the same

pressure as earth's at sea level but that point on Saturn would be

way up from the 'surface' but lower down it would be three times

greater gravitation. But if you were at the one bar depth wouldn't the

escape velocity still be about the same as earth? It seems it would

have to be. - 13 Mar '06 08:39This is how to calculate the escape velocity

v = sqrt(2*G*M/R

and the gravitation

g = G*M/R^2

where

v = escape velocity [m/s],

g = gravitation [m/s^2],

M = mass of the planet [kg],

R = distance from its center or radius [m] and

G = gravitational constant = 6.673x10^-11

Now you can test different planets and moons and even the sun itself.

If you calculate the density of Saturn by dividing its mass with its volume you'll find that its density is very low - even less than water, and therefore its radius is larger than it should be if it just was a rocky planet like the Earth.