Dr Helen Jane FraserThe Open University

helen.fraser@open.ac.uk

Dust Aggregation and the ELIPS Programme

AcknowledgementsMD work: Pavel Elkind; James Miller; John McCann

Observations: Alison Craigon; Jennifer Noble; Aleksi Suutarinen

Experiments: Jennifer Noble; Catherine Hill; Natalia Pascual; Alexander Driesmann

Collaborators: Dr. Klaus Pontoppidan (NASA), Prof. Y Aikawa (Kobe)

Prof. Francois Dulieu, Dr Emmanuel Congui (Observatoire de Paris / Cergy)Dr Stefan Anderson (Trondheim) Prof Gunar Nyman (Gothenberg)

Prof Thomas Loetering (Insbruck)Prof Harold Linnartz (Leiden) Dr Herma Cuppen (Nijmegen)

Prof. Jurgen Blum, Daniel Heisselmann (Braunchweig)Prof. Graeme Ackland (Edinburgh), Martin Uhrin (Imperial)

Prof. Dinko Chakarov (Chalmers)

e.g. large-scale MD simulations of ice structure & pore collapse

e.g. N-body simulationsof dust & ice aggregation‘bouncing’

& splinteringModelling ofEnvironment

Laboratory Experiments

RemoteObservations

TheoreticalChemistry / Physics

CURRENT RESEARCH

HIGHLIGHTS

e.g. • detecting icydebris disks

• moons of existing planets (Enceladus)

e.g. Ice MappingGas Depletion Mapping

e.g. Grain aggregationCollision induced

desorption / reaction

e.g. Chemical Kinetics & DynamicsDesorption

Chemical ReactivityDeuteration--------------

Energy transferIce structure & Pore Collapse

--------------

Dr Helen Jane FraserThe Open University

helen.fraser@open.ac.uk

“Understanding the earliest stages of planet formation: dust and ice collisions under

zero-g conditions”

Role of Icein “Star

and PlanetFormation”Is interstellar ice ‘sticky’? Does it ‘help’

planet building?

Credit: NASA/JPL-Caltech/R. Hurt (SSC)

Icy Grains in Protostellar Envelopes

Image courtesy of K Pontoppidan

adapted from an original idea in HJ Fraser, MP Collings and MRS McCoustra,

Review of Scientific Instruments, 2002, 73, 2161

Water Ice

Structure

< 150 –180 K

< 130 K

< 70 K

> 180 K

Ehrenfreund, Fraser, et. al. P&SS, 51, 473 (2003)

Al Halabi et. al.

JCP 120, 3358

(2004)

Al Halabi, Fraser

et. al. A&A, 422,

777 (2004)

H2O = most abundant condensed solid in ISM

McCann Sweatmann & Fraser, JCP (2011) in prep

Fraser & Miller JCP (2011) in prep

Wang et al ApJ ( 2005)

Credit: NASA/JPL-Caltech/R. Hurt (SSC)

Credit: David A. Hardy (ROE, ATC, NSF, NASA)

What do we need & why?pre-stellar phases& planet ‘building’

‘mature’ phasese.g. rings, debris disks, interplanetary dust, comets, KBO’s TNO’s

theory

Obs

expt

Particle diameter (cm)

10-4 10-2 10-1 101 102 104

Weidenschilling and Cuzzi [1993]

SERIOUS BOTTLENECKmm-cm sized particlesv = 1 cms-1 –1 ms-1

(How) do they stick?

Disk T = 180 K

•critical input for our planet formation simulations.

•parabolic flights = best way to do these experiments.

Observationalconstraints

Empiricaldata

Feedbackmodel – expt.

Testing ice as a glue.

Low velocity dust / ice collisions at LOW temperatureusing microgravity

Salter et al REVIEW SCIENTIFIC INSTRUMENTS (2009), 80, 074501

Optics use prism for ‘stereo view’

of collision volume

@ 48.8 deg.

Salter et al REVIEW SCIENTIFIC INSTRUMENTS (2009), 80, 074501

Low Temperature Stability

Velocity Ranges

I did this 248

times now (= 1 hr 30 mins 56 sec)

Aim =

Collide particles together – do they stick or bounce?

N-body simulations / kinetic theories – use single parameterThe co-efficient of restitution (ε)(a measure of KE dissipation)= relative velocities of particles before / after collision

mm-sized dust aggregates

in 1g conditions

1cms-1< v >1 ms-1

Parabolic flight

22sec

+0.01 < g > -0.01

Flight 1 – dust aggregate collisions (305 K)

Flight 2 – dust aggregate – target collisions (305 K)

Flight 3 – cold dust aggregate collisions (90< T >130 K)& cold dust + target

Flight 4 – mm – micron ice grain collisions (90 < T > 110 K)& cm ice particle collisions (120 < T > 150 K)

Heisselmann et al ICARUS (2010)

Heisselmann, Fraser & Blum, ApJ (in prep)

No discernable link with

ε and impact parameter

No discernable link with

ε and impact velocity

[As T rises with experiment duration,

no trend seen with

ε and temperature]

Heisselmann et al ICARUS (2010)

Small Icy particles @ low velocities

bounce!!

No real trend in ε

Modellers should add

all values in range

with equal probability

Heisselmann et al ICARUS (2010)

Parabolic Flight

Conclusions:Ice alone cannot account for simple sticking and growth of

particles from ‘ISM’ size grains to KBO’s TNO’s and planets – how does aggregation work?

Collisions involving icy particles (crystalline) are highly ‘inelastic’ but involve bouncing and erosion rather than sticking. KE is converted to rotational energy, and is reflected in the lack of correlation between the co-efficient of restitution and other parameters (impact velocity / angle / temperature)

It seems congregation of icy particles and resonant rotations may be key to building condensation (and planetary growth) events (see for e.g. Zsom et al A&A (2010); Dullemond et al. A&A (2011)).

This would indicate higher instances of collisions between particles, more cyclic ad-desorption events and outgassing. This has exciting prospects for chemical processing –collision induced desorption / reaction / deuteration?...

Outlook =

Need to use ASW NOT crystalline ice

Study effects of ‘dirty’ ices – mixed with dust + chemicals

Need to see population of small fragments < 1 micron in collisioni.e. clusters and gas yield

The IPE Experiment on the

International Space Station (ISS)

on behalf of the IPE team

and with thanks to Prof J Blum (lead scientist ICAPS)

& Astrid Orr Physical Sciences Coordinator

Directorate of Human Spaceflight and Exploration, ISS Utilisation Department, ESA

Why the ISS?

Particle diameter (cm)

10-4 10-2 10-1 101 102 104

Weidenschilling and Cuzzi [1993]

Small particles @ low velocities:-

Aggregation hindered by sedimentation

Highly porous particles collapse under their own gravity

Disk T = 180 K

•critical input for our planet formation simulations.

•parabolic flights = best way to do these experiments.

Interactions in Cosmic and Atmospheric Particle Systems � “IPE”(ICAPS Precursor Experiment)

Science Goals:

• Simulation of dust agglomeration e.g. in molecular clouds and star-forming regions

• Measurement of light scattering from these same aggregates (intensity, polarisation).

Blum et al. 2000

∅1.9 µm SiO2

“IPE”

Science Objectives

� Agglomeration through Brownian MotionDust-gas & dust-dust interactions

� Agglomeration through Laser Manipulation

Dust-gas-light & dust-dust

� Light scattering of aggregates (measurement of polarisation & intensity)

Dust-light

� Study of the Thermophoretic “Trap”Dust-gas

Physical Concepts

• Brownian Motion: Stochastic motion of particles in colloidal suspensions due to thermal

motion of the molecules of the fluid or gas.

• Van der Waals forces:Weak attractive or repulsive forces between molecules which can become

significant for very small dust grains (µm to nanometer size)

• ThermophoresisMotion of a particle within a gas, due to a thermal gradient in the gas

• PhotophoresisMouvement of a particle within a gas, due to a thermal gradient on the

particle, caused by illumination of the particle

Why study dust?Understand :

• the cycle of matter in the universe (plasma-gas-solid)

• the formation and composition of solid bodies around stellar systems: planets, comets

• the physics of planetary atmospheresPrepare:

• future space missions to the Moon, Mars, asteroids (robotic or with astronauts)

IPE experiment apparatus

•Experiment Chamber (EC) •Thermophoretic Trap (TP) •Particle manipulation system •Particle Injection Unit (PIU) •Cleaning system

Observation Systems:

•Overview Observation System•DHM/LDM Microscope •Light Scattering Unit (LSU) •Liquid Crystal variable retarder (LCVR) •Particle tracking

Courtesy of Qinetic Space

Experiment chamber

Content of chamber:

•Vacuum interface to PIU•Top and bottom cover•LSU ring window•Windows for other optical diagnostics•Thermophoretic trap•Cleaning unit•T-shield

Vacuum chamber: internal pressure: 0.1 to 100 mbarGas-type N2, Ar, He

Requirement on thermal gradients: < 0.01°°°°C/chamber radius !

Size of chamber: ∅ (inner) ∼10 cm

Thermophoretic trap

4-ring trap design

Requirement: “The Confining Trap shall not only trap the particles, it shall also force the particles tomove (if they are not in the centre).”

Breadboard built and tested at ZARM 2008, 2010

� extremely high requirements on the thermal control system

Columbus:

ESA's science laboratory on

the International Space

Station (ISS):

launched in Feb 2008

Columbus: for internal and external science payloads

The Columbus Module on ISS

IPE within the EPM“European Physiology Module” (EPM)

IPE Experiment Accommodation in the EPM Rack

EPM Rack Configuration

Role of the EPM rack

The EPM provides to the experiments modules:

• Mechanical supports and mechanical interfaces• Power Distribution Unit (PDU) • Ethernet Network• Air loop as thermal control system. • Interfaces to external power and data

resources• Computers , Laptop Unit

IPE Experiment Apparatus

Courtesy of QinetiQ Space (Verhaert Sp.)

Accomodation of items inside the experiment drawer