From Laboratory Measurements to the First In-Situ Analysis of Pristine Cometary Grains

Abstract

The microimaging dust analysis system (MIDAS) will be part of the payload of ESA’s Rosetta spacecraft4 to explore comet Wirtanen between 2011 and 2013. The launch of the spacecraft will take place in early 2003. MIDAS is based on an atomic force microscope, a technique which has made rapid progress in recent years after the discovery of the principle in 1986 by Binnig et al.1 The main scientific objective of MIDAS concerns the microtextural and statistical analysis of cometary dust grains and the project will resolve surface features with a spatial resolution of 4 nm in x and y direction and better than 1 nm in the z-direction. The comparative simplicity and robustness of the technique lends itself to space applications. The capabilities of the instrument are tailored to studies of the cometary environment and will provide an insight into the physical properties of dust grains that are not accessible otherwise. The prominent anticipated results are the size and texture of individual cometary grains and their building blocks in the range 4 nm to 5 μm. In preparation of the mission, a comprehensive measurement program of cosmic spherules and interplanetary dust grains has been initiated in order to build up experience in analyzing extraterrestrial particles with this technique. We present a description of the microscope and initial results from our AFM measurements on extraterrestrial material.