Rosetta has imaged the smallest grains of Comet 67P/Churyumov-Gerasimenko’s dust yet, with its Micro-Imaging Dust Analysis System, MIDAS.
Atomic force microscope topographic images of MIDAS particles A, B, and C. (a) Overview image with a pixel resolution of 312 nm and a colour scale representing height. (b) Sub-units (grains) of the individual particles detected at the resolution of the instrument are outlined. (c) 3D images of particles A and C with two times height exaggeration to aid visualisation. Particles A and C comprise tightly packed ‘compact’ grains, while B appears to be a single grain.
MIDAS works by collecting and then physically scanning grains with an Atomic Force Microscope. This uses a very fine tip, a bit like an old-fashioned record player needle, that is scanned over a particle. The deflection of the needle and therefore the height of the sample are measured to build up a 3D picture. This enables scientists to determine the structure of the particle, and thus gain insight into how it might have formed.
The new results, published in the journal Nature, provide evidence that dust particles continue to be aggregates below the size range already reported by the COSIMA instrument. That is, ...