MIDAS: Lessons learned from the first spaceborne atomic force microscope

Bentley, Mark S.; Arends, H.; Bütler, B.; Gavira, J.A.; Jeszenszky, H.; Mannel, Thurid; Romstedt, J.; Schmied, Roland; Torkar, K.

doi:10.1016/j.actaastro.2016.01.012

Cited by 16 publications

(33 citation statements)

References 21 publications

(26 reference statements)

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“…Like every AFM, MIDAS used sharp tips to raster the dust surface in order to obtain high resolution 3D images of nearly unaltered cometary dust. The finite width of the tips became a limiting factor when trying to access the smallest features of the dust particles (Bentley et al, 2016a). Therefore a 'reverse imaging mode' was developed, in which an on-board tip calibration sample with sharp spikes was used to probe cometary dust particles that had accumulated on the AFM tips during previous scans.…”

Section: Methodsmentioning

confidence: 99%

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Dust of comet 67P/Churyumov-Gerasimenko collected by Rosetta/MIDAS: classification and extension to the nanometer scale

Mannel

Bentley

Boakes

et al. 2019

A&A

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Context. 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. Aims. The cometary dust particle morphologies found at comet 67P on the micrometre scale are classified and their structural analysis extended to the nanometre scale. Methods. 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. Results. Three morphological classes can be determined, namely (i) fragile agglomerate particles of sizes larger than about 10 µm 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. Conclusions. The properties of the dust particles found by MIDAS represent an extension of the dust results of Rosetta to the micro-and nanometre scale. 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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Section: Methodsmentioning

confidence: 99%

“…During MIDAS normal imaging mode (a dynamic intermittent contact mode (Bentley et al, 2016a)) only low forces should be applied to the sample. Nevertheless, many of the cometary dust particles imaged fragmented, probably due to a high fragility, and dust was removed from the target or (partially) stuck to the tip.…”

Section: Methodsmentioning

confidence: 99%

Dust of comet 67P/Churyumov-Gerasimenko collected by Rosetta/MIDAS: classification and extension to the nanometer scale

Mannel

Bentley

Boakes

et al. 2019

A&A

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“…MIDAS operates in a slightly different way than most terrestrial AFMs, by making a careful approach to the sample at each pixel position and then moving away by a so-called retraction distance before moving to the next pixel, resulting in long scan times and possible distortion 13,14 . Distortion correction is performed using scans of on-board calibration targets, and polynomial background correction is used to remove height drifts.…”

Section: Data Acquisition and Calibrationmentioning

confidence: 99%

“…Flying on the Rosetta spacecraft, it collects dust on sticky targets during passive exposures and images its 3D topography with an unprecedented nanometre to micrometre resolution 13 .…”

mentioning

confidence: 99%

“…MIDAS, the Micro-Imaging Dust Analysis System 13,14 , is the first spaceborne atomic force microscope (AFM) and a unique instrument designed to measure the size, shape, texture and microstructure of cometary dust. Flying on the Rosetta spacecraft, it collects dust on sticky targets during passive exposures and images its 3D topography with an unprecedented nanometre to micrometre resolution 13 .…”

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confidence: 99%

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Aggregate dust particles at comet 67P/Churyumov–Gerasimenko

Bentley

Schmied

Mannel

et al. 2016

Nature

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Norway * These authors contributed equally to this workComets are believed to preserve almost pristine dust particles, thus providing a unique sample of the properties of the early solar nebula. The microscopic properties of this dust play a key role in particle aggregation during Solar System formation 1,2 . Prior to Rosetta cometary dust was considered to comprise irregular, fluffy agglomerates based on interpretation of remote observations in the visible and infrared [3][4][5][6] MIDAS, the Micro-Imaging Dust Analysis System 13,14 , is the first spaceborne atomic force microscope (AFM) and a unique instrument designed to measure the size, shape, texture and microstructure of cometary dust. Flying on the Rosetta spacecraft, it collects dust on sticky targets during passive exposures and images its 3D topography with an unprecedented nanometre to micrometre resolution 13 .Cometary dust was first collected in mid-November 2014. In this work we focus on particles collected from then until the end of February 2015. The collected particles cover a range of sizes from tens of micrometres down to a few 100 nanometres, and have various morphologies, from single grains to aggregate particles with different packing densities. Five examples are presented here. Figure 1 shows topographic images (height fields) of three particles (A, B and C). Particles A and C will be referred to as compact, since their sub-units (hereafter grains) are tightly packed, and B appears to be a homogeneous grain. The next example (D) is also a compact particle scanned with a higher lateral resolution of 80 nm (Fig. 2) -a factor four better than the previous scan. The final particle (E), presented in Fig. 3, is best described as a loosely packed "fluffy" aggregate comprising many grains. Detailed collection times and geometries for all particles can be found in Extended Data Fig. 1-3.Aided by the 3D nature of the data, individual grains can be identified, as shown in Fig. 1b, Fig. 2b and 1.09 −0.25 +0.01 µm in size, again similar to the grains in A-C. However, the higher resolution reveals that this micrometre-sized particle is itself an aggregate of smaller units; seven grains can be resolved, with sizes ranging from 260 −120 +50 nm to 540 −250 +20 nm. The visible part of particle E has a maximum extent of 14 µm in X and 37 µm in the Y direction. Analysis of its component grains (Fig. 3d) shows sizes in the range from 0.58 −0.20 +0.15 to 2.57 −0.51 +004 µm with the grain heights ranging between 0.2 µm and 3 µm with 90% smaller than 1.7 µm. These measurements are the first evidence for a continuation of the aggregate nature of dust particles below the size range observed by COSIMA (10s-100s micrometres) 15 .Particle E also shows a morphology strongly reminiscent of stratospheric chondritic porous (CP) IDPs, long suspected of having a cometary origin. This link is consistent with observations by COSIMA for larger dust particles, which also measured similar compositions for dust at 67P and IDPs 15,16 . One notable difference to IDPs is the extre...

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