Microgravity experiments on the collisional behavior of saturnian ring particles

Heißelmann, D.; Blum, Jürgen; Fraser, H. J.; Wolling, Kristin

doi:10.1016/j.icarus.2009.08.009

Cited by 63 publications

(83 citation statements)

References 46 publications

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“…This demonstrates that the limit of coefficient of restitution decreases with increasing impact velocity, which is corroborated by Güttler et al (2012) and Krijt et al (2013). It is also possible that this is a result of deviation from sphericity (compared to the results of Heißelmann et al (2010) who used almost perfectly spherical samples) or due to the smaller size of our particles.…”

Section: Coefficient Of Restitution and Impact Parametersupporting

confidence: 86%

“…7a, the coefficients of restitution have an upper limit of 0.65. Similar experiments by Heißelmann et al (2010) on collisions of 1.5 cm (diameter) ice spheres in the velocity range 0.06-0.22 m s −1 gave an upper limit of 0.84 (also shown in Fig. 7a).…”

Section: Coefficient Of Restitution and Impact Parametersupporting

confidence: 74%

“…5. The coefficients of restitution are slightly lower on average than those reported for 1.5 cm (diameter) sized spheres at impact velocities of 0.06-0.22 m s −1 (Heißelmann et al 2010), which were spread from 0.0 to 0.84, suggesting that there is a velocity effect at play with lower velocities giving a greater limit of coefficient of restitution. It is also possible that this effect could be due to the smaller size of our particles (between 4.7 and 10.8 mm).…”

Section: Discussioncontrasting

confidence: 61%

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Collisions of small ice particles under microgravity conditions

Hill

Heißelmann

Blum

et al. 2014

A&A

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Context. Planetisimals are thought to be formed from the solid material of a protoplanetary disk by a process of dust aggregation. It is not known how growth proceeds to kilometre sizes, but it has been proposed that water ice beyond the snowline might affect this process. Aims. To better understand collisional processes in protoplanetary disks leading to planet formation, the individual low velocity collisions of small ice particles were investigated. Methods. The particles were collided under microgravity conditions on a parabolic flight campaign using a purpose-built, cryogenically cooled experimental setup. The setup was capable of colliding pairs of small ice particles (between 4.7 and 10.8 mm in diameter) together at relative collision velocities of between 0.27 and 0.51 m s −1 at temperatures between 131 and 160 K. Two types of ice particle were used: ice spheres and irregularly shaped ice fragments. Results. Bouncing was observed in the majority of cases with a few cases of fragmentation. A full range of normalised impact parameters (b/R = 0.0-1.0) was realised with this apparatus. Coefficients of restitution were evenly spread between 0.08 and 0.65 with an average value of 0.36, leading to a minimum of 58% of translational energy being lost in the collision. The range of coefficients of restitution is attributed to the surface roughness of the particles used in the study. Analysis of particle rotation shows that up to 17% of the energy of the particles before the collision was converted into rotational energy. Temperature did not affect the coefficients of restitution over the range studied.

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Section: Coefficient Of Restitution and Impact Parametersupporting

confidence: 86%

Section: Coefficient Of Restitution and Impact Parametersupporting

confidence: 74%

Section: Discussioncontrasting

confidence: 61%

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Collisions of small ice particles under microgravity conditions

Hill

Heißelmann

Blum

et al. 2014

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“…More recent experiments showed that collisions of mm-to cm-sized aggregates often result in bouncing (e.g., Weidling et al 2009;Heißelmann et al 2010;Weidling et al 2012;Jankowski et al 2012). Extrapolating the results obtained from the various experiments, Güttler et al (2010) devised a model describing the outcome of collision with respect to the collision velocity, and the mass and porosity of the colliding aggregates.…”

Section: Introductionmentioning

confidence: 99%

Bouncing behavior of microscopic dust aggregates

Seizinger

Kley

2013

A&A

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Context. Bouncing collisions of dust aggregates within the protoplanetary disk may have a significant impact on the growth process of planetesimals. Yet, the conditions that result in bouncing are not very well understood. Existing simulations studying the bouncing behavior used aggregates with an artificial, very regular internal structure. Aims. Here, we study the bouncing behavior of sub-mm dust aggregates that are constructed applying different sample preparation methods. We analyze how the internal structure of the aggregate alters the collisional outcome and we determine the influence of aggregate size, porosity, collision velocity, and impact parameter. Methods. We use molecular dynamics simulations where the individual aggregates are treated as spheres that are made up of several hundred thousand individual monomers. The simulations are run on graphic cards (GPUs). Results. Statistical bulk properties and thus bouncing behavior of sub-mm dust aggregates depend heavily on the preparation method. In particular, there is no unique relation between the average volume filling factor and the coordination number of the aggregate. Realistic aggregates bounce only if their volume filling factor exceeds 0.5 and collision velocities are below 0.1 ms −1 . Conclusions. For dust particles in the protoplanetary nebula we suggest that the bouncing barrier may not be such a strong handicap in the growth phase of dust agglomerates, at least in the size range of ≈100 µm.

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“…Numerical modeling, including all different kinds of collisions then result in a boucing barrier ). However, the most pronounced input is that only rebound was observed in collisions of mm-size aggregates in the relevant domain of low collision velocities (Heißelmann et al 2010;Weidling et al 2012). The experiments that are important used dust with grain sizes of about 1 μm.…”

Section: Resultsmentioning

confidence: 99%

Crossing barriers in planetesimal formation: The growth of mm-dust aggregates with large constituent grains

Jankowski

Wurm

Kelling

et al. 2012

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Collisions of mm-size dust aggregates play a crucial role in the early phases of planet formation. It is for example currently unclear whether there is a bouncing barrier where millimeter aggregates no longer grow by sticking. We developed a laboratory setup that allowed us to observe collisions of dust aggregates levitating at mbar pressures and elevated temperatures of 800 K. We report on collisions between basalt dust aggregates of from 0.3 to 5 mm in size at velocities between 0.1 and 15 cm/s. Individual grains are smaller than 25 μm in size. We find that for all impact energies in the studied range sticking occurs at a probability of 32.1 ± 2.5% on average. In general, the sticking probability decreases with increasing impact parameter. The sticking probability increases with energy density (impact energy per contact area). We also observe collisions of aggregates that were formed by a previous sticking of two larger aggregates. Partners of these aggregates can be detached by a second collision with a probability of on average 19.8 ± 4.0%. The measured accretion efficiencies are remarkably high compared to other experimental results. We attribute this to the relatively large dust grains used in our experiments, which make aggregates more susceptible to restructuring and energy dissipation. Collisional hardening by compaction might not occur as the aggregates are already very compact with only 54 ± 1% porosity. The disassembly of previously grown aggregates in collisions might stall further aggregate growth. However, owing to the levitation technique and the limited data statistics, no conclusive statement about this aspect can yet be given. We find that the detachment efficiency decreases with increasing velocities and accretion dominates in the higher velocity range. For high accretion efficiencies, our experiments suggest that continued growth in the mm-range with larger constituent grains would be a viable way to produce larger aggregates, which might in turn form the seeds to proceed to growing planetesimals.

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Microgravity experiments on the collisional behavior of saturnian ring particles

Cited by 63 publications

References 46 publications

Collisions of small ice particles under microgravity conditions

Collisions of small ice particles under microgravity conditions

Bouncing behavior of microscopic dust aggregates

Crossing barriers in planetesimal formation: The growth of mm-dust aggregates with large constituent grains

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