Kuiper Belt, a disk-shaped region of space, extending beyond the orbit of Neptune, in which a very large number of minor planets are in orbit around the sun. These bodies, called Kuiper Belt objects (or trans-Neptunian objects), are generally less than 200 miles (320 km) in diameter, although some are larger. Quaoar, discovered in 2002, has a diameter of about 800 miles (1,300 km). Astronomers believe Kuiper Belt objects are composed of rock and ice and that some become comets. The discovery in 1992 of the object named 1992 QB1 provided the first observational evidence for the existence of the Kuiper Belt. The region is named after astronomer Gerard Kuiper, who theorized about distant objects in the solar system.
Since the 19th century, humans have wondered about the prospect of life on Mars. While we haven't sent anyone to the Martian surface, we have sent spacecrafts, which have gathered a good amount of information on what it's like on Mars. How is it different from Earth? How is it similar? And could life really have existed there long ago, or exist in the future?
Neptune is the eighth planet from the sun, the fourth largest, and a gas planet. It is named after the Roman god of the sea. Neptune is four times the size of Earth, and its day lasts a little more than16 hours. Its year is about 165 Earth years. Neptune's orbit is a perfect circle. The last stop on spacecraft Voyager's epic trip through the solar system was the gas giant Neptune.