|
|||||
|
|
A giant crater on 90 Antiope? |
|
| Authors: | P Descamps F Marchis T Michalowski J Pollock M Birlan F Vachier M Fauvaud F Pilcher |
| Institution: | a Institut de Mécanique Céleste et de Calcul des Éphémérides, Observatoire de Paris, UMR 8028 CNRS, 77 av. Denfert-Rochereau, 75014 Paris, France b University of California at Berkeley, Department of Astronomy, 601 Campbell Hall, Berkeley, CA 94720, USA c SETI Institute, 515 N. Whisman Road, Mountain View, CA 94043, USA d Astronomical Observatory, Adam Mickiewicz University, Sloneczna 36, 60-286 Poznan, Poland e Appalachian State University, Department of Physics and Astronomy, 231 CAP Building, Boone, NC 28608, USA f Wiggins Observatory, 472 Country Club, Tooele, UT 84074-9665, USA g Observatoire du Bois de Bardon, 16110 Taponnat, France h Observatoire de la Côte d’Azur, BP 4229, 06304 Nice Cedex 4, France i Organ Mesa Observatory, 4438 Organ Mesa Loop, Las Cruces, NM 88011, USA j Magdalena Ridge Observatory, New Mexico Tech, Socorro, NM 87801, USA |
| Abstract: | Mutual event observations between the two components of 90 Antiope were carried out in 2007-2008. The pole position was refined to λ0 = 199.5 ± 0.5° and β0 = 39.8 ± 5° in J2000 ecliptic coordinates, leaving intact the physical solution for the components, assimilated to two perfect Roche ellipsoids, and derived after the 2005 mutual event season (Descamps, P., Marchis, F., Michalowski, T., Vachier, F., Colas, F., Berthier, J., Assafin, M., Dunckel, P.B., Polinska, M., Pych, W., Hestroffer, D., Miller, K., Vieira-Martins, R., Birlan, M., Teng-Chuen-Yu, J.-P., Peyrot, A., Payet, B., Dorseuil, J., Léonie, Y., Dijoux, T., 2007. Figure of the double Asteroid 90 Antiope from AO and lightcurves observations. Icarus 187, 482-499). Furthermore, a large-scale geological depression, located on one of the components, was introduced to better match the observed lightcurves. This vast geological feature of about 68 km in diameter, which could be postulated as a bowl-shaped impact crater, is indeed responsible of the photometric asymmetries seen on the “shoulders” of the lightcurves. The bulk density was then recomputed to 1.28 ± 0.04 g cm−3 to take into account this large-scale non-convexity. This giant crater could be the aftermath of a tremendous collision of a 100-km sized proto-Antiope with another Themis family member. This statement is supported by the fact that Antiope is sufficiently porous (∼50%) to survive such an impact without being wholly destroyed. This violent shock would have then imparted enough angular momentum for fissioning of proto-Antiope into two equisized bodies. We calculated that the impactor must have a diameter greater than ∼17 km, for an impact velocity ranging between 1 and 4 km/s. With such a projectile, this event has a substantial 50% probability to have occurred over the age of the Themis family. |
| Keywords: | Asteroids Rotation Surfaces Satellites of asteroids Eclipses Photometry |
| 本文献已被 ScienceDirect 等数据库收录！ | |