Stardust Interstellar Preliminary Examination I: Identification of tracks in aerogel

Andrew J. Westphal , David Anderson , Anna L. Butterworth , David R. Frank , Robert Lettieri , William Marchant , Joshua Von Korff , Daniel Zevin , Augusto Ardizzone , Antonella Campanile , Michael Capraro , Kevin Courtney , Mitchell N. Criswell , Dixon Crumpler , Robert Cwik , Fred Jacob Gray , Bruce Hudson , Guy Imada , Joel Karr , Lily Lau Wan Wah , Michele Mazzucato , Pier Giorgio Motta , Carlo Rigamonti , Ronald C. Spencer , Stephens B. Woodrough , Irene Cimmino Santoni , Gerry Sperry , Jean-Noel Terry , Naomi Wordsworth , Tom Yahnke , Carlton Allen , Asna Ansari , Saša Bajt , Ron K. Bastien , Nabil Bassim , Hans A. Bechtel , Janet Borg , Frank E. Brenker , John Bridges , Donald E. Brownlee , Mark Burchell , Manfred Burghammer , Hitesh Changela , Peter Cloetens , Andrew M. Davis , Ryan Doll , Christine Floss , George Flynn , Zack Gainsforth , Eberhard Grün , Philipp R. Heck , Jon K. Hillier , Peter Hoppe , Joachim Huth , Brit Hvide , Anton Kearsley , Ashley J. King , Barry Lai , Jan Leitner , Laurence Lemelle (1) , Hugues Leroux , Ariel Leonard , Larry R. Nittler , Ryan Ogliore , Wei Ja Ong , Frank Postberg , Mark C. Price , Scott A. Sandford , Juan-Angel Sans Tresseras , Sylvia Schmitz , Tom Schoonjans , Geert Silversmit , Alexandre S. Simionovici , Vicente A. Solé , Ralf Srama , Thomas Stephan , Veerle J. Sterken , Julien Stodolna , Rhonda M. Stroud , Steven Sutton , Mario Trieloff , Peter Tsou , Akira Tsuchiyama , Tolek Tyliszczak , Bart Vekemans , Laszlo Vincze , Michael E. Zolensky

1 LGL-TPE - Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement

Here, we report the identification of 69 tracks in approximately 250 cm2 of aerogel collectors of the Stardust Interstellar Dust Collector. We identified these tracks through Stardust@home, a distributed internet-based virtual microscope and search engine, in which 30,000 amateur scientists collectively performed 9 \texttimes 107 searches on approximately 106 fields of view. Using calibration images, we measured individual detection efficiency, and found that the individual detection efficiency for tracks 2.5 μm in diameter was 0.6, and was 0.75 for tracks 3 μm in diameter. Because most fields of view were searched 30 times, these results could be combined to yield a theoretical detection efficiency near unity. The initial expectation was that interstellar dust would be captured at very high speed. The actual tracks discovered in the Stardust collector, however, were due to low-speed impacts, and were morphologically strongly distinct from the calibration images. As a result, the detection efficiency of these tracks was lower than detection efficiency of calibrations presented in training, testing, and ongoing calibration. Nevertheless, as calibration images based on low-speed impacts were added later in the project, detection efficiencies for low-speed tracks rose dramatically. We conclude that a massively distributed, calibrated search, with amateur collaborators, is an effective approach to the challenging problem of identification of tracks of hypervelocity projectiles captured in aerogel.

Domaines: Planète et Univers [physics]

Andrew J. Westphal, David Anderson, Anna L. Butterworth, David R. Frank, Robert Lettieri, et al.. Stardust Interstellar Preliminary Examination I: Identification of tracks in aerogel. Meteoritics and Planetary Science, 2014, 49 (9), pp.1509--1521. ⟨10.1111/maps.12168⟩. ⟨hal-02351161⟩