A new study suggests that the planet Jupiter may have been hit a long time ago by a still-developing planet, one about 10 times the size of Earth. Scientists believe the head-on crash took place not long after Jupiter was formed. Scientists say such a violent collision could explain conditions inside the center of the planet. A report on the study appeared in the publication Nature. Astronomers believe the collision may have happened several million years after the formation of our sun. The solar system, made up of the sun and eight major planets, was formed about 4.6 billion years ago. Jupiter is massive, more than two times the size of all other planets in the solar system combined. Jupiter is a gaseous planet, made up mostly of hydrogen and helium.