Dust of comet 67P/Churyumov-Gerasimenko collected by Rosetta/MIDAS: classification and extension to the nanometre scale. (arXiv:1907.01266v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Mannel_T/0/1/0/all/0/1">T. Mannel</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bentley_M/0/1/0/all/0/1">M.S. Bentley</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Boakes_P/0/1/0/all/0/1">P.D. Boakes</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Jeszenszky_H/0/1/0/all/0/1">H. Jeszenszky</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ehrenfreund_P/0/1/0/all/0/1">P. Ehrenfreund</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Engrand_C/0/1/0/all/0/1">C. Engrand</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Koeberl_C/0/1/0/all/0/1">C. Koeberl</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Levasseur_Regourd_A/0/1/0/all/0/1">A.C. Levasseur-Regourd</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Romstedt_J/0/1/0/all/0/1">J.Romstedt</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Schmied_R/0/1/0/all/0/1">R. Schmied</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Torkar_K/0/1/0/all/0/1">K. Torkar</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Weber_I/0/1/0/all/0/1">I. Weber</a>
The properties of the smallest subunits of cometary dust contain information
on their origin and clues to the formation of planetesimals and planets.
Compared to IDPs or particles collected during the Stardust mission, dust
collected in the coma of comet 67P/Churyumov-Gerasimenko during the Rosetta
mission provides a resource of minimally altered material with known origin
whose structural properties can be used to further the investigation of our
early Solar System. A novel method is presented to achieve the highest spatial
resolution of imaging possible with the MIDAS Atomic Force Microscope on-board
Rosetta. 3D topographic images with resolutions of down to 8,nm are analysed
to determine the subunit sizes of particles on the nanometre scale. Three
morphological classes can be determined, namely (i) fragile agglomerate
particles of sizes larger than about 10,$mathrm{mu m}$ comprised by
micrometre-sized subunits that may be again aggregates and show a moderate
packing density on the surface of the particles; (ii) a fragile agglomerate
with a size about few tens of micrometres comprised by micrometre-sized
subunits suggested to be again aggregates and arranged in a structure with a
fractal dimension less than two; (iii) small, micrometre-sized particles
comprised by subunits in the hundreds of nanometres size range that show
surface features suggested to again represent subunits. Their differential size
distributions follow a log-normal distribution with means about 100,nm and
standard deviations between 20 and 35,nm. All micrometre-sized particles are
hierarchical dust agglomerates of smaller subunits. The arrangement, appearance
and size distribution of the smallest determined surface features are
reminiscent of those found in CP IDPs and they represent the smallest directly
detected subunits of comet 67P.
The properties of the smallest subunits of cometary dust contain information
on their origin and clues to the formation of planetesimals and planets.
Compared to IDPs or particles collected during the Stardust mission, dust
collected in the coma of comet 67P/Churyumov-Gerasimenko during the Rosetta
mission provides a resource of minimally altered material with known origin
whose structural properties can be used to further the investigation of our
early Solar System. A novel method is presented to achieve the highest spatial
resolution of imaging possible with the MIDAS Atomic Force Microscope on-board
Rosetta. 3D topographic images with resolutions of down to 8,nm are analysed
to determine the subunit sizes of particles on the nanometre scale. Three
morphological classes can be determined, namely (i) fragile agglomerate
particles of sizes larger than about 10,$mathrm{mu m}$ comprised by
micrometre-sized subunits that may be again aggregates and show a moderate
packing density on the surface of the particles; (ii) a fragile agglomerate
with a size about few tens of micrometres comprised by micrometre-sized
subunits suggested to be again aggregates and arranged in a structure with a
fractal dimension less than two; (iii) small, micrometre-sized particles
comprised by subunits in the hundreds of nanometres size range that show
surface features suggested to again represent subunits. Their differential size
distributions follow a log-normal distribution with means about 100,nm and
standard deviations between 20 and 35,nm. All micrometre-sized particles are
hierarchical dust agglomerates of smaller subunits. The arrangement, appearance
and size distribution of the smallest determined surface features are
reminiscent of those found in CP IDPs and they represent the smallest directly
detected subunits of comet 67P.
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