Dating antarcic meteorites
The primary ones were decay of short-lived radioactive isotopes within the bodies and collisions between the bodies as they grew.
As a result, the interiors of larger bodies experienced substantial melting, with consequent physical and chemical changes to their constituents.
Prairie soil is largely derived from fine glacial loess and contains few large rocks.
The collectors realized that there was a reasonable chance that any rocks the farmers unearthed would include meteorites.
Fewer than 1 percent of meteorites are thought to come from the Moon or Mars.
On the other hand, there is good reason to believe that a significant fraction of the micrometeorites found drifting down through Earth’s upper atmosphere come from comets.
For further discussion of the sources of meteorites and the processes by which they are brought to Earth, meteor and meteoroid: Reservoirs of meteoroids in space and Directing meteoroids to Earth.Indeed, certain meteorites do appear to preserve very ancient material, some of which predates the solar system.The effect of the final impact with the ground of meteoroids about a kilogram or less in mass is usually an anticlimax.In the outer solar system the formation of Jupiter, Saturn, and the other giant planets is thought to have involved more than simple aggregation, but their moons—and comets—probably did form by this basic mechanism.Available evidence indicates that asteroids and comets are leftovers of the intermediate stages of the aggregation mechanism.