Deutsches Zentrum für Luft- und Raumfahrt e.V. German Aerospace Center Institut für Planetenforschung Institute of Planetary Research Department: “ASTEROIDS and COMETS” X. Re port 2006/2007 Comets Asteroids Technology Space Missions MODELS http://solarsystem.dlr.de From left to right Dr. Ekkehard Kührt [email protected] Section leader Dr. Alan W. Harris [email protected] Deputy section leader Dr. Gerhard Hahn [email protected] Scientific staff member Nikolaos Gortsas [email protected] PhD student Dr. Stefano Mottola [email protected] Scientific staff member Dr. Detlef de Niem [email protected] Scientific staff member Dr. Jörg Knollenberg [email protected] Scientific staff member Not appearing in the photo: Prof. Uwe Motschmann [email protected] Guest scientist Dr. Carmen Tornow [email protected] Scientific staff member Dr. Michael Solbrig [email protected] Engineer 2 1 Introduction (Kührt).................................................................................................. 4 2 Asteroid Science ....................................................................................................... 4 2.1 Investigations of the physical properties of asteroids with the Spitzer Space Telescope (Harris, Müller)....................................................................................... 4 2.2 Asteroid thermal modelling (Mueller, Harris) .......................................................... 5 2.3 Spectroscopic observations of 12 NEAs with UKIRT (Harris) .................................... 6 2.4 Asteroid search and follow-up programmes (Hahn)................................................ 6 3 Comet science.......................................................................................................... 7 3.1 Thermo-physical modeling of cometary nuclei with moving ice boundaries (Gortsas, Kührt, Motschmann)............................................................................... 7 3.2 Hybrid Simulation Studies of Anisotropic Cometary Plasma Sources (Gortsas, Motschmann, Kührt, Knollenberg )........................................................................ 7 4 Primitive bodies and the planetary system ................................................................. 8 4.1 Impact phenomena (de Niem, Kührt, Motschmann) ............................................... 8 4.2 From the Solar Nebula to minor bodies (Tornow, Kührt, Motschmann)................. 10 5 Space Missions ....................................................................................................... 11 5.1 BepiColombo-MERTIS (Knollenberg) ................................................................... 11 5.2 Rosetta-Mupus (Knollenberg) .............................................................................. 11 5.3 DAWN (Mottola, Kührt)....................................................................................... 12 5.4 Don Quijote: A hazardous asteroid mitigation pre-cursor mission (Harris) ............. 12 6 Technology projects................................................................................................ 13 6.1 HP3 (Knollenberg)................................................................................................ 13 6.2 FIREWATCH (Kührt, Knollenberg, Behnke) ........................................................... 13 7 Scientific Prospects ................................................................................................. 14 7.1 HGF-Alliance (Tornow, Kührt, Motschmann, Harris) ............................................. 14 7.2 AsteroidFinder (Mottola, Kührt, Hahn, Michaelis, Harris) ...................................... 15 8 Appendix................................................................................................................ 16 8.1 Scientific publications in refereed journals and books (submitted or published 2006-2007)......................................................................................................... 16 8.2 Scientific publications in other journals and proceedings (published 2006-2007) .. 18 8.3 Minor Planet Circulars/Electronic Circulars............................................................ 18 8.4 Publications in the popular literature and public outreach .................................... 20 8.5 Observing Campaigns 2006, 2007....................................................................... 21 8.6 Space mission responsibilities............................................................................... 21 8.7 Space Mission proposals...................................................................................... 22 8.8 Other events and activities................................................................................... 22 8.9 Funding sources .................................................................................................. 22 3 1 Introduction (Kührt) This 10th annual report describes the research results of the “Asteroids and Comets” Department of the Institute of Planetary Research (PF) of the DLR (German Aerospace Center) during the years 2006 and 2007. Presently, the Department consists of 8 scientists, 1 PhD student, 1 diploma student and two guest scientists, one from the University of Padua, Italy, and one from the Technical University Braunschweig. Our scientific goal is to investigate minor bodies in the Solar System by observing them in the visible and infrared wavelength ranges, defining and contributing to relevant space missions and modelling physical processes associated with this class of object. Other fields of interest are risk evaluation of impacts of Near Earth Objects (NEOs) on our home planet, the origin of life and the transfer of space technology to solve environmental problems on Earth. Scientific interest in the minor bodies of the Solar System is focussed mainly on their crucial role in the formation of the planets and the development of life. Asteroids and comets are thought to be remnant material from the process of formation and the initial development of planets. Due to their peculiar dynamical and physical properties, such as small size, lack of a permanent atmosphere, and relatively little thermal processing, these objects have remained largely unaltered since the time of Solar System formation. Their dynamical evolution is a tracer of the mass distribution in the early planetary system. Highlights of the period covered by this report include: • 31 refereed papers in 2006/07. • The DAWN space probe was launched to investigate Ceres and Vesta. Two staff members (S. Mottola, E. Kührt) belong to the science team. • Our mission proposal AsteroidFinder was selected in a review process for a launch with a DLR compact satellite in 2012. • The PF proposal “Planetary evolution and life” with major contributions from our Department was selected by the HGF. Funding will be provided for a 5-year period. • A staff member (Alan Harris) was awarded the title “DLR Senior Scientist”. • Michael Müller successfully defended his PhD thesis obtaining an excellent result. • Some issues with the MUPUS hardware onboard of Rosetta were successfully resolved by means of software uploads. In Chapters 1 to 4 we report on our scientific results. Contributions to space missions and our activities in technology transfer are described in Sections 5 and 6. Scientific prospects are discussed in Section 7 and the appendix summarises publications, project contributions, observation campaigns, public outreach activities, and our funding. 2 Asteroid Science 2.1 Investigations of the physical properties of asteroids with the Spitzer Space Telescope (Harris, Müller) The Karin cluster: Our programme of observations of 17 members of the Karin cluster in the main asteroid belt was completed in 2007. The programme (PI: Harris) includes a total of 7 co- investigators from Europe and the USA. The cluster, Fig. 2.1 Spitzer Space Telescope. 4 named after its largest member, (832) Karin, is believed to have been formed only 5.8±0.2 Myr ago in a catastrophic collision. The cluster is of great interest due to the fact that the physical properties of its members may preserve unique information about asteroid fragmentation and surface processes on small asteroids, which include regolith formation and modification of albedo and spectral properties via space weathering. We have determined the sizes and albedos of all objects observed and found evidence for unusually high thermal inertia in a few cases. The albedos of the observed targets are very similar. The mean value, excluding Karin, is pV = 0.18, with a standard error of only 0.01; this compares with pV = 0.15 ± 0.06 for the asteroid Karin itself. Our results strongly support the premise that the family members are taxonomically related. The thermal inertia governs the magnitude of the Yarkovsky effect, i.e. the gradual drift of an asteroid’s orbit due to the momentum carried off by thermal photons. Our observations should assist in determining whether the observed spread in the orbital parameters of the family members since their formation is consistent with the expected magnitude of the Yarkovsky effect. First results were presented at the DPS meeting #39, Orlando, in October 2007. Analysis of the final data set is still in progress. The potential spacecraft target 1989 ML: We were awarded director’s discretionary time with Spitzer in 2006 to determine the albedo and taxonomic type of the potential spacecraft target (10302) 1989 ML. This NEA has been proposed as a target for several