Planets by definition are required to have achieved hydrostatic equilibrium, and thus have a spherical shape - and not a highly rough, irregular shape like many smaller asteroids. In order to achieve this they need to be quite massive. So one might say, all planets have a large spherical shape; the largest in our solar system being Jupiter.
Because of their rotation, planets are slightly oblate (or squished at the poles, as oppsed to spherical prolation which would be be slightly stretched).
No i am sorry to say mars is not an exact sphere. the rocks and boulders and everything on the planet is not an exact sphere
Sphere
its a sphere
a sphere
It orbits the sun. It is large enough to form into a sphere (not difficult for a gas/ice giant). It has cleared its orbit of debris.
Generallly speaking, it spherical. The planet is small, but still has a large enough mass and gravity to pull it into this shape. As with earth, it has lots of lumps and bumps on it's surface.
This is a very vauge question as it could refer to anything from the surface of the sun, to the Earth, to many things beyond the sun. 1) if by sphere you mean the sun, then the closest layer is that is not part of the sun is the plasma sphere. 2) if by sphere you men the Earth layers, then the Exosphere is the closest. 3) if by sphere you mean a body that is large enough to be considered a planet, the answer is Mercury, since the other bodies in the area maybe closer but they are not large enough to be sphere shaped.
That picture represents the planet Saturn. The sphere is the planet itself, while the ring symbolizes its iconic ring system that surrounds it.
Sphere, orb, planet.
biosphere
Planet?
planet, world, earth, sphere, orb