It is narrow in the middle. On top is a large ring-like structure.

VOA: special.2009.03.04

This term is used especially for plants like herbs that produce new growth year after year from the same root structure.

VOA: special.2009.07.21

Marc Rayman says Vesta appears to have a layered structure, one that is similar to planets like Earth, Mars and Venus.

VOA: special.2011.07.27

The structure was meant to look like a "flying saucer,"

VOA: special.2009.03.04