Planetary Science by Space Missions
Composition of Interstellar Dust Crossing our Solar System
During the formation of our solar system, most presolar dust grains were destroyed or heavily processed. A minor population of circumstellar presolar grains survived processing in the protosolar disk and can be recognized by their extremely diverse isotopic composition. In contrast, the solar system as part of our galaxy, is constantly subject to interstellar material made of dust and gas, that passes through our solar system. These contemporary interstellar dust particles (IDP) can be analyzed in situ from a spacecraft or can be captured and brought back to Earth by a sample-return mission. In the framework of the DFG Priority Program “The first 10 Million years of the Solar System” (SPP1385), our group worked on both of these approaches, as described below.
The Cosmic Dust Analyser (CDA) aboard the Cassini spacecraft for the first time carried out compositional in situ analysis of contemporary interstellar dust. In a 10-year campaign the mass spectrometer of the instrument recorded impact ionization spectra of 36 IDP (Altobelli, Postberg et al., Science 2016). These findings changed the view on processing of dust & gas in interstellar space.
In 2000 and 2002 the Stardust Mission exposed aerogel collector panels and aluminum foil for a total of about 200 days to the stream of interstellar grains sweeping through the solar system. The material was brought back to Earth in 2006. In our project we carry out laboratory calibration experiments of the collection process by shooting sub-micron, high speed [3 - 30km/s] interstellar dust (ISD) analogues onto Stardust aerogel flight spares and aluminum foils. This helped to verify the dynamics and composition of grains captured in the Stardust aerogel and craters of presumably interstellar origin in the aluminum foil (Postberg et al, MAPS 2014 / Westphal et al., Science 2014). Our results further indicate that probably about 100 ISD grains have not yet been recovered from the aerogel samplers, thus the search for further grains continues.