Friday 19th October Sol 72

One of the main aims of the scoops has been to get soils and
dust of suitable fine grained size for the X-ray diffraction experiment –
CHEMIN.  We are waiting with excitement
for the first results.  X-ray photons from
the radioactive Cobalt-60 source are diffracted at specific angles which depend
on the X-ray photon wavelength and the atomic lattice thickness (‘d-spacing’) of the
mineral grain.  The set of d spacings are
unique to each mineral.  The
Curiosity instrument uses transmission geometry ie X-rays are transmitted through
the thin layer of scooped grains, and a piezo stage to vibrate the sample and
so evenly mix it and help measure all the possible d-spacings.  It is
critical that the sample is fine grained with numerous different crystal orientations so
that all the necessary reflections will be measured.

One of the things we will get are an image from the CCD detector with rings, the diameters of which show the diagnostic mineral lattice spacings.