Gaspra and the Flora family: fragments of an ancient collision

What Gaspra's young surface and grooves say about the collision that created thousands of sibling asteroids.

Published 2026-10-23

Gaspra is not alone. It belongs to the Flora family, a large group of asteroids sharing similar orbits in the inner main belt — fragments of a collision long ago.^[4][3]

A big family

The Flora family has more than 13,000 known members, about 3.5% of all main-belt asteroids. Its largest member, 8 Flora, is about 140 km across and holds about 80% of the family's mass; most other members are smaller than 30 km.^[4] Gaspra, about 12 km across, is a medium-sized member near the family's core.^[2][4]

Reading Gaspra's surface

Gaspra has relatively few large craters. One likely reason is that the collision that produced the Flora family — and Gaspra — happened relatively recently on astronomical timescales.^[3] Crater counts suggest a surface age of roughly 20 to 300 million years.^[3]

Gaspra's long grooves, 100–300 m wide and tens of meters deep, may be linked to its violent birth in that family-forming collision.^[3] Its pitted grooves also hint that the surface is covered by a layer of loose regolith, which Gaspra may have gained during the same impact.^[3]

Clues about the parent body

Gaspra is unusually olivine-rich for an S-type asteroid.^[3] Studies of Gaspra suggest the Flora parent body was at least partly differentiated — heated enough for some layering — and that the family is on the order of 200 million years old.^[4]

Meteorites and the dinosaurs?

Flora family members are considered good candidates for the parent bodies of the L chondrite meteorites, which make up about 38% of meteorites striking Earth.^[4] Some researchers have also suggested that the family may be the source of the impactor that created the Chicxulub crater, linked to the extinction of the dinosaurs — an idea that remains debated.^[4]

Numbered citations link to the sources list on the Gaspra overview page.