Comets are big lumps of ice that came into the solar system from outer space. When the comet came close to the sun, the heat makes them to start to evaporate. Gas and dust form long tails that we can see from Earth and the tails can be millions of m iles long. In 1985 to 1986, a space craft called Giotto visited the most famous comet and the most recent visit to the inner solar system is the comet named Halley. In 1993, the comet Shoemaker-Levy was trapped by Jupiter's gravity and it plunged into Jup iter's atmosphere. In 1996 and 1997, we saw the comet Hyakutake and the comet Hale-Bopp. Hale-Bopp was the brightest comet seen on Earth.