Radar imaging of Asteroid 7 Iris

• Published in: Icarus
• Main Authors: Ostro, S. J., Magri, C., Benner, L. A. M., Giorgini, J. D., Nolan, M. C., Hine, A. A., Busch, M. W., Margot, J. L.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Elsevier 2010
• Subjects: Asteroids; Radar observations; South Pole; South pole
• Online Access: https://doi.org/10.1016/j.icarus.2009.11.011

Arecibo radar images of Iris obtained in November 2006 reveal a topographically complex object whose gross shape is approximately ellipsoidal with equatorial dimensions within 15% of 253 × 228 km. The radar view of Iris was restricted to high southern latitudes, precluding reliable estimation of Iris' entire 3D shape, but permitting accurate reconstruction of southern hemisphere topography. The most prominent features, three roughly 50-km-diameter concavities almost equally spaced in longitude around the south pole, are probably impact craters. In terms of shape regularity and fractional relief, Iris represents a plausible transition between ~50-km-diameter asteroids with extremely irregular overall shapes and very large concavities, and very much larger asteroids (Ceres and Vesta) with very regular, nearly convex shapes and generally lacking monumental concavities. © 2009 Elsevier Inc. Received 26 June 2009; revised 10 October 2009; accepted 7 November 2009. Available online 24 November 2009. Steve Ostro, deceased, led the radar observations of 7 Iris, played the principal role in the analysis of those data, and created several drafts of this paper, nearly bringing the process to completion before his untimely death on December 15, 2008. His determination in the face of illness was remarkable. The second author then supervised the completion of the manuscript (primarily by composing Fig. 1 and the Appendix) and handled the editorial process. We thank the Arecibo technical and support staffs for help with the radar observations. The Arecibo Observatory is part of the National Astronomy and Ionosphere Center, which is operated by Cornell University under a cooperative agreement with the National Science Foundation (NSF). We thank M. Kaasalainen for kindly providing information regarding the Iris lightcurve data set, E. Asphaug for helpful discussions, and an anonymous reviewer and I. de Pater for constructive reviews that improved the presentation of this work. C. Magri was partially supported by NSF Grant ...