Brand new evidence from the NEAR Shoemaker probe points in this direction. It's another great science detective story, with help from the sun. A huge solar flare caused Eros to be bathed in especially strong X-rays on May 4. These are the chondritic meteorites.
Most scientists now believe such rocks are the basic building blocks of the solar system.
This smooth mixture of elements fits nicely into current thinking about how the rocky planets in our system formed, including the Earth itself. Think of incredibly huge amounts of dust floating about. Some of these particles naturally collide with each other, and stick together. The resulting clumps get bigger and bigger. Gravity works its magic on these clumps, now called planetesimals, which keep colliding.