are made of planetary material, silicates (sand), minerals, rocks and very little metal.
Collected fragments are ordinary chondrites, stony meteorites
that make up 85% of all meteorites recovered.
Most meteorites are stony and of the stony meteorites
, almost all (90 percent) are what are called ordinary chondrites.
New evidence from old rocks suggests that many of the precious metals mined today were delivered to the planet by stony meteorites
called chondrites in a bombardment that lasted for hundreds of millions of years.
On the red planet, iron meteorites are more common than stony meteorites
, probably because they are better at resisting erosion.
The majority of stony meteorites
are chondrites, so named because they contain chondrules--spherical grains of silicate materials unlike anything found on Earth.
Small, stony meteorites
typically break up high in the atmosphere (SN: 7/19/03, p.
Initial tests revealed that the large rock is an ordinary chondrite - stony meteorites
that are commonly found in Earth.
Ground-based observations indicate that Vesta represents the only known parent of a class of stony meteorites
called basaltic achondrites.
Unlike the more common iron and stony meteorites
, carbonaceous chondrites are thought to be made of material that has never undergone heating or pressure since the earliest days of the solar system.
The relative abundance of certain long-lived radioactive isotopes in stony meteorites
suggests that the galaxy ranges in age from 9 to 15 billion years.
The group's initial goal was to identifythe fine-grained type of carbon contained in many primitive, stony meteorites