Physical characterization of very young asteroid families

Recently four very young families were discovered: the Datura, Emilkowalski, 1992 YC2, and Lucascavin clusters are 450 ± 50, 220 ± 30, 50-250, and 300-800 kyr old, respectively. To date, these clus- ters are the only known asteroid families younger than 1 Myr. The Datura cluster is a group of seven asteroids while the three other new families are groups of three objects each. All these objects have diameters in the ~ 1-11 km range with >60% of the objects having D< 2km. These discoveries offer an excellent opportu- nity for physical studies of young families whose members have suffered limited erosion. It is known that a planetary surface exposed to space weathering effects (solar wind ion irradiation, cosmic rays and interplanetary dust bombardment) changes in color and spectral characteristics. The effect, in the inner part of the solar system, is a progressive darkening of the surfaces, and a reddening of the reflectance spectra. In the case of these families we expect the surfaces to be young (quite unweathered). Especially, the relatively precise dating of the fragmentation events will allow us to put a time tag on the effects of space weathering. We will present visible (0.45-0.95 µm) and near-infrared (0.7-2.5 µm) spectroscopic observations for 1270 Datura and 14627 Emilkowalski and a visi- ble spectrum for 21509 Lucascavin. Results: We will show that the surfaces, even if young, have already undergone some significant amount of space weathering (SW). These observations prone a fast acting SW process responsible for these reddish colors.