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Flora family


The Flora or Florian family of asteroids is a large grouping of S-type asteroids in the inner main belt, whose origin and properties are relatively poorly understood at present. Roughly 4–5% of all main belt asteroids belong to this family.

Because of its poorly defined boundaries, and the location of Flora itself near the edge, this asteroid group has also sometimes been called the Ariadne(an) family, when Flora did not make it into the group during an analysis (e.g. the WAM analysis by Zappala 1995).

The Flora family of asteroids may be the source of the Chicxulub (Cretaceous–Paleogene) impactor, the likely culprit in the extinction of the dinosaurs.

The largest member is 8 Flora, which measures 140 km in diameter, and comprises about 80% of the total family mass. Nevertheless, the parent body was almost certainly disrupted by the impact/s that formed the family, and Flora is probably a gravitational aggregate of most of the pieces.43 Ariadne makes up much of the remaining mass (about a further 9%), with the remaining family members being fairly small, below 30 km in diameter.

A noticeable fraction of the parent body has been lost from the family since the original impact, presumably due to later processes such as e.g. secondary collisions. For example, it has been estimated that Flora contains only about 57% of the parent body's mass (Tanga 1999), but about 80% of the mass in the present family.

The Flora family is very broad and gradually fades into the background population (which is particularly dense in this part of space) in such a way that its boundaries are very poorly defined. There are also several non-uniformities or lobes within the family, one cause of which may have been later secondary collisions between family members. Hence, it is a classical example of a so-called 'asteroid clan' (see asteroid family). Curiously, the largest members, 8 Flora and 43 Ariadne, are located near the edge of the family. The reason for this unusual mass distribution within the family is unknown at present.


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