Date: 1993 - 1999 Are planets made out of dirt or rock? Could
another planet hit earth? Well, dirt or rock is pretty much the
same thing, isn't it? Dirt is just ground up rock... Actually,
only the inner 4 planets of our solar system (Mercury, Venus,
Earth, Mars) are mostly made of rock, like the Earth is. The
outer planets (Jupiter, Saturn, Uranus, Neptune, Pluto) are made
of "lighter" things, like hydrogen, helium, ammonia, and
probably some water. However, these planets (except Pluto) have
so much of these "lighter" elements that they are much much
heavier than the Earth is. The planets right now all orbit the
sun in very nice almost circular orbits. The diameters of those
orbits differ by 10 million miles or more, and the planets them
selves are only a few thousand miles in diameter, so there's no
way one planet could come close to hitting another. The only
exception to this is Pluto, that has a much more non-circular
(elliptical) orbit than any of the others, and which sometimes
crosses Neptune's orbit.