Annual Progress Report for NASA Planetary Astronomy Program Project
“Physical Observations of Very Young Dynamical Families of Asteroids”
Principal Investigator: Clark R. Chapman () Southwest Research Institute (SwRI)
Suite 400, 1050 Walnut St.
Boulder, CO 80302
Co-Investigators: William J. Merline (SwRI)
David Nesvorný (SwRI)
Eliot F. Young (SwRI)
Collaborators: Petr Pravec (Astron. Inst., Ondrejov, Czech R.)
2 March 2005
Introduction
The goals of this project are to study, with various telescopic techniques, the physical properties of members of very young dynamical families. These families, identified by Co-I Nesvorny and his colleagues, were formed at discrete and well-determined times less than 10 million years ago. Most asteroid families are expected to be hundreds or even billions of years old. Our expectation is that young families, as compared with typical families, may provide vital clues to processes that presumably take place on relatively short timescales. Processes that we are interested in include space weathering, temporary preservation of near-surface volatiles, satellite formation and evolution, the Yarkovsky Effect (which we can help to calibrate), and understanding the initial/early configurations of asteroid families as a check on hydrocode simulations and other theoretical insights concerning the formation of families.
Our approach is to observe known members of the Karin cluster (a=2.87 AU, e=0.044, i=2.1º), the Veritas family (a=3.17 AU, e=0.065, i=9.3º), and the Iannini cluster (a=2.64 AU, e=0.267, i=12.2º), plus controls (e.g. non-Karin members of the Koronis family), using a variety of telescopes, instruments, and techniques. Our approach is to make coordinated space-based and ground-based observations of relevant family members, obtaining low- and medium-resolution spectrophotometry, radiometry, adaptive optics imaging, and lightcurve photometry.
Progress During First 9 Months
Funding arrived in late May 2004. Here we briefly report progress in obtaining initial observations for this program through February 2005, including near-term plans we have made for future observing.
Observations to date have been obtained chiefly for members of the young Veritas family (C-type), the young Karin family (S-type), and the Koronis family (control). These include VLT AO observations obtained in July 2004 (and we are also incorporating analogous data obtained in February 2004, as well as earlier data from Keck and Gemini); IRTF/MIRSI radiometry at 2 different wavelengths on 11/3/04 and 12/8/04 for several Veritas and Koronis members plus 1 Karin member; 12 observations at 8um with S/N 10-30 with Spitzer, split roughly equally between Karin family and Koronis controlds, as presented at the recent AAS meeting (P.Tamblyn, W.J. Merline, C.R. Chapman, D. Nesvorny, D.D. Durda 2005, "Space- and Ground-Based Observations of Exceptionally Young Asteroids", BAAS 205, 56.09); 2 weeks of V lightcurves and/or UBVRI color observations, using a CTIO 1-m telescope in mid-October 2004, on 9 Karin members, 3 Veritas members, 1 Iannini member, and 7 Koronis controls; 4 partly usable nights 11/30/04-12/4/04 on a KPNO 0.9m telescope (MOSAIC visible CCD) but less successful than the CTIO run; another KPNO MOSAIC run in mid-February 2005, but mostly rained out. These observing runs represent good initial accomplishment, although we have yet to settle on exactly the most effective telescopes/instruments to meet our goals. We have considered obtaining spectrophotometry with IRTF, but have not yet done so, concentrating first on the radiometry.
Several future runs are already scheduled, or are in the works. Contacts have been made concerning utilization of other telescopes. For example, we have scheduled a week in late-May 2005 on the KPNO 2.1m for spectrophotometry. We have an AO run sceduled for late June on the IRTF, which may be applied to our young family members if an appulse is available.
Needless to say, it is premature to attempt any analysis or synthesis of the very partial data set so far obtained, but we are encouraged by our successful observations.