Acceleration due to gravity at the surface of Mars is given by the formula
[tex]g_m = \frac{GM}{R^2}[/tex]
here
M = mass of Mars
R = radius of Mars
Now if we take a point which is at height 3 times the radius of Mars from its surface
So the acceleration due to gravity is given as
[tex]g = \frac{GM}{(3R+R)^2}[/tex]
now using this
[tex]g = \frac{GM}{16R^2}[/tex]
[tex]g = \frac{g_m}{16}[/tex]
so here the gravity is 16 times lesser than gravity at surface