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
“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