How come most satellites/moons are spheres?

Question

I know Mars moons are most likely capture asteroids, and they are spherical in shape, so why is it that the other planets moons are spherical? If it's true that the earth's moon was a broken off piece of the earth, then how come it is spherical and Mar's satellites aren't?

Answer 1

Most natural satellites are spheroidal because they are massive enough for gravity to pull them into that shape. This condition is called hydrostatic equilibrium. I think you meant to say that Mars' moons are *not* spherical in shape, which is correct, and that's because they are not very massive. Even though Earth's moon probably formed as the result of a giant impact, it was not really a single chunk that blew off. The outer portion of the Earth and the impactor were both pulverized, and became an orbiting cloud. It was massive enough and far enough from Earth that its own gravity due to its mass was able to pull it together into a spheroidal body.

Answer 2

Most planets are spherical because this is the shape which can contain the most mass for the smallest volume.

I do not think the moon is a broken off piece of the Earth.

Although planets are nor perfectly round, they certainly are more spherical in shape than any other shape.

Answer 3

The larger moons are spherical because their own gravity is strong enough to pull them into that shape. Smaller moons such as those of Mars are too small to be pulled into a spherical shape. In other words, their own rigidity is stronger than their gravitational force, so they can reatin irregular shapes.

The Earth's moon was not broken off so much as blasted off by a large impact. It is quite large enough to be pulled into a sphere by its own gravity even as a solid mass, but even if it were not, the impact meant that the Moon was in a liquid state when it first formed from the accretion of debris from the impact.

Answer 4

All mass on or near a moon is attracted toward its center of gravity. As a moon is formed the mass of its original parts fall toward the center of mass, and potential energy (elevation) is converted to kinetic energy (velocity) which on impact with the center (or existing layer) is converted to heat energy. Also decay of radioactive elements in the mix give off heat. If the mass of the moon is large enough to reach high temperatures it will 'melt' and form a near perfect sphere surrounding the center of gravity. On earth, water (melted ice) covers 3/4 of the earth's surface forming a near perfect sphere, neglecting tides and the spin of the earth that enlarges the equator and slightly flattens the poles. Asteroids have too little mass and too little heat to melt.

Answer 5

What you are saying is not true at all, Jupiter and Saturn have some small potato shaped moons but they are small and dead so who really cares. The reason all the Major (big) moons are sphere is because they are big and their gravity pulls them into a ball.

Answer 6

u should know that the most imp and strong force act on heavenly bodies is gravitational force,
due to their own gravitational pull, planets and moons tend to minimize their surface area,and u shoul know that for a perticular volume, spherical shapes have minimum surface area,

Answer 7

Gravity pulling them inward with equal pressure. Those that are woppydo dont have enough gravity themselves to pull them into a sphere.