A natural solid object (metallic or stony/silicate) larger than 10 µm (microns) that has traveled through space, by natural means from the celestial body on which it formed, and has landed on Earth or other planetary body or artificial body/satellite (larger than itself). Most meteorites come from asteroids, but a small number found on Earth come from the Moon (see Lunar meteorites) or Mars (see Martian meteorites). Meteorite types include: iron, stony iron, chondrite, carbonaceous chondrite, and achondrite. A primitive meteorite is defined as a chondrite that experienced minimal heating and aqueous alteration on its parent asteroid. Primitive meteorites have the highest concentrations of presolar grains. (See "Meteors, Meteorites, and Impacts" from The Eight Planets website. ) Meteorites between 10 µm (microns) and 2 mm in size are called "micrometeorites. " Meteorites collected on Earth are named for the location where they are found.