A New Growth Model for Protoplanetary Dust Aggregates Carsten Güttler & Jürgen Blum Institut für Geophysik und extraterrestrische Physik, TU Braunschweig, Germany Dust in Planetary Systems Friedrich Schiller Universität, Jena September 27 th to October 1 st 2010 PRESENTATION WITHOUT MOVIE FILES. PLEASE REQUEST FROM OR

Güttler & Blum: A New Growth Model for Protoplanetary Dust Aggregates From Dust to Planets dust ~1 µm planetesimals e.g. 1 km agglomeration Interaction with gas dominant gravitation negligible Blum et al., 1998 Dominik & Tielens, 1997 see also: Blum & Wurm, 2000 ? Comet Temple 1 © NASA/JPL-Caltech/UMD Poppe et al., 2000a

Güttler & Blum: A New Growth Model for Protoplanetary Dust Aggregates Outline 1.The Collision Model laboratory experiments 2.Results: Application of the Model consequences for the evolution of dust 3.Discussion of Results critical inspection of the model 4.New Experiments future improvements of the model

Güttler & Blum: A New Growth Model for Protoplanetary Dust Aggregates 1. Overview on Collisional Outcomes Güttler et al., 2010

Güttler & Blum: A New Growth Model for Protoplanetary Dust Aggregates 1. Overview on Collisional Outcomes Güttler et al., 2010

Güttler & Blum: A New Growth Model for Protoplanetary Dust Aggregates S1: Hit & Stick  Sticking without any restructuring if E impact < 5 · E roll  Physical description and simulation: Dominik & Tielens (1997)  Experiments: Blum & Wurm (2000) Blum & Wurm, 2000 Blum & Wurm, 1998 Blum et al., 1998

Güttler & Blum: A New Growth Model for Protoplanetary Dust Aggregates S2: Sticking by Surface Effects  Collisions can lead to sticking although the hit- and-stick threshold velocity is exceeded  Explanation: aggregate is compacted, contact area increases → more contacts support sticking size: 0.2 mm; velocity: 0.24 m/s Kothe, Güttler & Blum, unpublished data

Güttler & Blum: A New Growth Model for Protoplanetary Dust Aggregates B1: Bouncing with Compaction I  Collisions between mm-sized aggregates hardly lead to sticking  Bouncing for low velocities (<1m/s) Heißelmann, Fraser & Blum, mm v rel = 0.4 m/s

Güttler & Blum: A New Growth Model for Protoplanetary Dust Aggregates B1: Bouncing with Compaction II Weidling et al., mm

Güttler & Blum: A New Growth Model for Protoplanetary Dust Aggregates 1. Possible Collisional Outcomes

Güttler & Blum: A New Growth Model for Protoplanetary Dust Aggregates The Collision Model x axes: velocity cm/s y axes: mass g

Güttler & Blum: A New Growth Model for Protoplanetary Dust Aggregates 1. The Collision Model

Güttler & Blum: A New Growth Model for Protoplanetary Dust Aggregates Outline 1.The Collision Model laboratory experiments 2.Results: Application of the Model consequences for the evolution of dust 3.Discussion of Results critical inspection of the model 4.New Experiments future improvements of the model

Güttler & Blum: A New Growth Model for Protoplanetary Dust Aggregates 2. The Monte-Carlo Growth Model  Dust growth in a box in the protoplanetars disk  Fast Monte Carlo code (Zsom & Dullemond, 2008)  Aggregates possess physical properties (i.e. mass, porosity), which determine the collisional outcome  Monte Carlo character: collision probabilities determine the next collision to compute  Model parameters: r=1AU; α =10 -4 ; T=200K; Σ 0 =1700 g/cm 2 (MMSN)

Güttler & Blum: A New Growth Model for Protoplanetary Dust Aggregates 2. Which Collisions Do Really Occur?  Dust growth in a box in the protoplanetary disk (Zsom & Dullemond, 2008)  Model parameters: r=1AU; α =10 -4 ; T=200K; Σ 0 =1700 g/cm 2 (MMSN) Zsom et al., 2010

Güttler & Blum: A New Growth Model for Protoplanetary Dust Aggregates 2. How do the Aggregates Grow?  Mass Evolution  max ~1g  Bouncing inhibits further growth  Porosity Evolution  very fluffy aggregates after ~1000 years  Bouncing compacts aggregates Zsom et al., 2010

Güttler & Blum: A New Growth Model for Protoplanetary Dust Aggregates 2.Overview of Collisions  Many collisions do not occur within the experiment-boxes  Extrapolations by orders of magnitude  New experiments are being designed to check the 'hot-spots' Zsom et al., 2010

Güttler & Blum: A New Growth Model for Protoplanetary Dust Aggregates Outline 1.The Collision Model laboratory experiments 2.Results: Application of the Model consequences for the evolution of dust 3.Discussion of Results critical inspection of the model 4.New Experiments future improvements of the model

Güttler & Blum: A New Growth Model for Protoplanetary Dust Aggregates  Sizes of protoplanetary dust aggregates:  Mass ratios of projectile and target:  Collision velocities of protoplanetary dust aggregates:  Porosities of protoplanetary dust aggregates:  Protoplanetary dust materials and temperatures: 1 µm1 mm1 kmx1 m m/s10 -2 m/s100 m/sx1 m/s oxides/metals >1000 K silicates ~300 K ices ~100 K organics ~200 K no expt’sexpt’s compactvery porousxporous 0 1x1x 3. How Complete is the Model?

Güttler & Blum: A New Growth Model for Protoplanetary Dust Aggregates 3. How Solid are the Threshold Lines? experiments and MD simulations model based on Hertzian theory based on experiments bouncing dominates porosity model exclusively based on Weidling et al.

Güttler & Blum: A New Growth Model for Protoplanetary Dust Aggregates 3. Improvement of Monte Carlo Method  Previous simulations in a local, static box (no global particle motion)  0D  Recent simulations with many boxes, including differential settling and turbulent mixing  1D

Güttler & Blum: A New Growth Model for Protoplanetary Dust Aggregates Zsom, Ormel, Dullemond & Henning, in prep. midplane 1 pressure scale height 2 pressure scale heights

Güttler & Blum: A New Growth Model for Protoplanetary Dust Aggregates Outline 1.The Collision Model laboratory experiments 2.Results: Application of the Model consequences for the evolution of dust 3.Discussion of Results critical inspection of the model 4.New Experiments future improvements of the model

Güttler & Blum: A New Growth Model for Protoplanetary Dust Aggregates 4. Sticking and Bouncing Güttler et al., 2010

Güttler & Blum: A New Growth Model for Protoplanetary Dust Aggregates 4. Collisional Outcomes Weidling et al., unpublished  Microgravity experiment (drop tower, suborbital flight)  Particle diameter: mm  Initial velocity ~0.1m/s  Collisional cooling down to mm/s

Güttler & Blum: A New Growth Model for Protoplanetary Dust Aggregates Two bouncing collision v = 17 cm/s (first) v = 14 cm/s (second) particle size: mm 4. Bouncing I particle diameter: 1 mm filling factor: 40% 47 analyzed collisions: 6xsticking 40xbouncing 1xfragmentation Weidling et al., unpublished

Güttler & Blum: A New Growth Model for Protoplanetary Dust Aggregates Bouncing collision v = 12 mm/s particle size: mm 4. Bouncing II particle diameter: 1 mm filling factor: 40% 47 analyzed collisions: 6xsticking 40xbouncing 1xfragmentation Weidling et al., unpublished

Güttler & Blum: A New Growth Model for Protoplanetary Dust Aggregates Sticking collision v = 9 mm/s particle size: mm 4. Sticking particle diameter: 1 mm filling factor: 40% 47 analyzed collisions: 6xsticking 40xbouncing 1xfragmentation Weidling et al., unpublished

Güttler & Blum: A New Growth Model for Protoplanetary Dust Aggregates 4. Relation to Collision Model scheduled for 11/2010 to be analyzed Weidling et al., unpublished

Güttler & Blum: A New Growth Model for Protoplanetary Dust Aggregates 4. Bouncing and Fragmentation

Güttler & Blum: A New Growth Model for Protoplanetary Dust Aggregates 4. Laboratory Drop Tower  Laboratory drop tower  Two aggregates collide in free fall  Two falling cameras, 1.5 m drop height  Velocities from 1 cm/s to 3 m/s Beitz et al., in prep.

Güttler & Blum: A New Growth Model for Protoplanetary Dust Aggregates 4. Low-Velocity Collisions 2cm diameter, 50% filling factor, velocity: 10 mm/s 2cm diameter, 50% filling factor, velocity: 1.8 m/s

Güttler & Blum: A New Growth Model for Protoplanetary Dust Aggregates 4. Fragmenting Collisions  bouncing for v < 20 cm/s  fragmentation with mass transfer for v > 20 cm/s Beitz et al., in prep. also see poster by Jens Teiser et al.

Güttler & Blum: A New Growth Model for Protoplanetary Dust Aggregates 4. Revised Fragmentation Threshold? Beitz et al., in prep.

Güttler & Blum: A New Growth Model for Protoplanetary Dust Aggregates 4. Fragmentation with Mass Transfer Kothe, Güttler & Blum, accepted by ApJ

Güttler & Blum: A New Growth Model for Protoplanetary Dust Aggregates Kothe, Güttler & Blum, accepted by ApJ 4. Fragmentation with Mass Transfer II

Thank you for your attention! This work was funded by the Deutsche Forschungs- gemeinschaft (DFG) under grant Bl 298/14-1 and by DLR under grant 50WM0936. We thank René Weidling, Eike Beitz, and Stefan Kothe for providing their unpublished data. Additional information on the presented model can be found in Güttler et al. (2010, A&A) and Zsom et al. (2010, A&A).