This project is embedded in the unique ESA mission Rosetta which ensures vivid international cooperation. Besides the exchange at scientific workshops of the Rosetta community this proposal seeks strong cooperation with the scientists of the other dust experiments GIADA (PI: Prof. Alessandra Rotundi) and COSIMA (PI: Dr. Martin Hilchenbach) and the MIDAS Co-Investigators team.

The project is led from IWF, Graz, where the MIDAS PI is hosted. This institute is the center for all activities around MIDAS, such as the development of the instrument, the operation during the mission, and the scientific data analysis as well as the data archiving.

The MIDAS team at IWF Graz is embedded in the former Planetary Surface Science working group that is involved in a variety of projects around comets and granular surfaces as, e.g., the international CoPhyLab project (https://www.cophylab.space/index.php?id=home).

During this project we forged cooperations to work in depth on the following topics:

The hardness of cometary dust at the nanometre scale: MIDAS force curve measurements

Prof. Jürgen Blum, Dr. Bastian Gundlach, Lea Klaiber MSc, Polina Skachkova (TU Braunschweig).
Dr. Mark Bentley (European Space Astronomy Centre ESA – ESAC, Madrid)
H.-J. Butt, M. Kappl (Max-Planck-Institut für Polymerforschung, Mainz)

The force with which the smallest, 100nm-sized grains of dust particles from comet 67P stick together is investigated and compared to reference material on Earth. The MIDAS instrument recorded so called force curves using the tip of the atomic force microscope to push onto the dust particles, often compacting and crushing them. The data reveal a surprisingly high material hardness of cometary dust at the 100 nm scale. To understand which materials have a similar hardness and response to force curve measurements, several comparative laboratory measurements were acquired: for polystyrene with a common atomic force microscope, and for cometary analogue material (SiO2 spheres) with the MIDAS Flight Spare instrument available on Earth. Further measurements with a variety of materials are planned. In the end, we will be able to conclude on the nanoscale properties of cometary dust, i.e. its hardness and a possible material composition.

Results:

The structure of cometary dust particles: comparison to COSIMA data and simulations

Dr. Jérémie Lasue, Isabelle Maroger MSc., Dr. Ph Garnier, (Univ. Toulouse)
Dr. Robert Botet (Univ. Paris-Saclay)
Prof. Anny-Chantal Levasseur-Regourd (Sorbonne Univ. Paris)
Dr. Sihane Merouane (MPS Göttingen)
Dr. Mark Bentley (European Space Astronomy Centre ESA – ESAC, Madrid)

The structure of the particles collected on targets, like it is the case for the COSIMA and the MIDAS instrument on board the Rosetta comet orbiter, may be altered by the impact on the collector surface depending on the dust particle’s structure, speed,  and internal strength. This project aims to understand the alteration of the dust by comparing COSIMA and MIDAS data to simulations.

In a first part of the project it was investigated how the dust structures observed in the COSIMA instrument can be explained. A major question is if the extremely porous particles with fractal dimension around 1.8 that are observed by MIDAS (see Mannel et al. 2016 in MNRAS 462) and GIADA may also exist in the COSIMA dataset. The comparison of the simulation result with the COSIMA dataset indicates that the most favourable explanation for the observed structures would be that two populations exist, one with a fractal dimension around 2, and one with a compact structure of fractal dimensions between 2.5 and 3. The results of this study are published in Lasue et al. 2019 in Astron. Astrophys 630.

A second part of the project is envisioned to directly compare the structures detected by MIDAS with those in COSIMA and the simulations. This would further the understanding of the alteration of dust particles upon impact, and also strengthen the link between COSIMA and MIDAS observations.

Results:

  • Paper:
    Flattened loose particles from numerical simulations compared to particles collected by Rosetta
    Lasue, J., I. Maroger, R. Botet, Ph. Garnier, S. Merouane, Th. Mannel, A.C. Levasseur-Regourd, M.S. Bentley, Astron. Astrophys, 630, A28, 2019.
    https://doi.org/10.1051/0004-6361/201834766
  • Talk at European Geosciences Union (EGU) 2018:
    Compacted aggregates from numerical simulations compared to Rosetta collected particles 
    Maroger, Isabelle; Lasue, Jérémie; Botet, Robert; Garnier, Philippe; Merouane, Sihane; Mannel, Thurid; Levasseur-Regourd, Anny-Chantal; Bentley, Mark
    https://ui.adsabs.harvard.edu/abs/2018EGUGA..2012523M/abstract
  • Talk at the 49th Lunar and Planetary Science Conference 2018:
    Compacted Loose Particles from Numerical Simulations Compared to Rosetta Collected Particles
     Maroger, I.; Lasue, J.; Botet, R.; Garnier, Ph.; Merouane, S.; Mannel, Th.; Levasseur-Regourd, A. C.; Bentley, M. S.
    https://ui.adsabs.harvard.edu/abs/2018LPI....49.2149M/abstract

Characterization of cometary activity of 67P/Churyumov-Gerasimenko

(ISSI team of Dr. Longobardo)

A. Longobardo, V. Della Corte, A. Rotundi, M. Fulle, G. Rinaldi, M. Formisano, V. Zakharov, S. Ivanovski, T. Mannel, M. Ciarniello, L. Inno, M. Rubin, E. Palomba, H. Cottin, F. Dirri, P. Palumbo, C. Güttler, S. Merouane, C. Tubiana, B. Pestoni, Z. Dionnet.

This project investigates the activity of comet 67P by linking results of dust emission, morphology and composition together with nucleus surface properties. It also aims to offer new insights about the formation and evolution of the comet.

To date, an algorithm was developed that links dust detections in the coma with potential emission regions on the cometary surface. It is examined if certain dust properties as detected by Rosetta instruments can be linked with certain surface morphologies. In a first published paper (Longobardo et al. 2020 in MNRAS 496) GIADA detections of fluffy and compact particles are linked to the comet nucleus surfaces of either rough or smooth appearance. Fluffy and compact particles seem to have common ejection regions and maintain their spatial connection up to an altitude of 10km. Afterwards, fluffy particles get dispersed in the coma. Regarding their origin on the nucleus surface, fluffy particles seem to be more abundant in rough terrains; this is in agreement with the assumption that fluffy particles are a pristine resource that stem mostly from the more pristine, rough terrains.

Currently the comparison between the dust analysing instruments in on going. Especially the GIADA and MIDAS data are compared and trends in e.g. particle flux and size distribution checked.

Results:

  • Paper:
    67P/Churyumov–Gerasimenko’s dust activity from pre- to post-perihelion as detected by Rosetta/GIADA
    A. Longobardo, V. Della Corte, A. Rotundi, M. Fulle, G. Rinaldi, M. Formisano, V. Zakharov, S. Ivanovski, T. Mannel, M. Ciarniello, L. Inno, M. Rubin, E. Palomba, H. Cottin, F. Dirri, P. Palumbo, C. Güttler, S. Merouane, C. Tubiana, B. Pestoni, Z. Dionnet. Monthly Notices of the Royal Astronomical Society 496, 2020.
    https://doi.org/10.1093/mnras/staa1464
  • Talk at EPSC 2020:
    Merging data from Rosetta GIADA and MIDAS dust detectors to characterize 67P’s activity
    Andrea Longobardo et al. in Session SB3 – Comets, Centaurs, Trans-Neptunian and interstellar objects