Comets are composed of a solid core of rock, ice and dust and are covered by a thin and gaseous atmosphere of more ice and dust, called a coma. They melt as they approach the Sun, releasing a stream of gas and dust blown from their surface by solar radiation and plasma and forming a cloud and outward tail.
Comets drift toward the inner Solar System when various gravitational forces remove them from the Oort cloud, becoming more visible as they get closer to the heat given off by the Sun. Fewer than a dozen comets are discovered each year by observatories around the world.
This comet last passed Earth at a time when Neanderthals still lived in Eurasia, our species was expanding its reach beyond Africa, bringing large Ice Age mammals including mammoths and saber-toothed cats into the landscape and North Africa was a wet, fertile and rainy place.
According to California Institute of Technology physics professor Thomas Prince, the comet may provide clues about the early Solar System as it formed during the early stages of the Solar System.