Two subclasses of cestodes are differentiated on the basis of the numbers of larval hooks, the Cestodaria being decacanth (10 hooks) and the Eucestoda being hexacanth (6 hooks). Collectively, 14 orders of cestodes have been identified according to differences in parasite morphology and developmental cycles.
Most meteorites originate between Mars and Jupiter, where a belt of asteroids has lingered for 4.5 billion years, since the solar system was young. No rock on Earth is as old as a meteoriteâall terrestrial material has been ground, melted, and reformed by plate tectonics. Meteorites have other, less common, origins. Meteor impacts on the moon or Mars can eject surface material into space that ends up on Earth. Last year a 10.5-ounce meteorite that originated on Mars fetched $94,000. A 4-pound lunar meteorite, the most expensive ever auctioned, sold for $330,000 in 2012.
More generally, a meteorite on the surface of any celestial body is a natural object that has come from outer space. Meteorites have been found on the moon and Mars. Meteorites that are recovered after being observed as they transit the atmosphere or impact the Earth are called meteorite fall.All other meteorites are known as finds. meteorite is a solid piece of debris from a source such as an asteroid or a comet, which originates in outer space and survives its impact with the Earth's surface. It is called a meteoroid before its impact.