Evidence of large-scale radial mixing in the early solar nebula from measurements of meteoroid bulk density Jean-Baptiste Kikwaya 1,2,3, P. Brown 2,3, and M. Campbell-Brown 2,3 1 Vatican Observatory, V Vatican City State 2 Meteor Physics Group, Dept. Of Physics and Astronomy, University of Western Ontario 3 Centre for Planetary Science and Exploration, University of Western Ontario

Meteor Kitt Peak, AZ ( N, W)Whipple Obs, AZ ( N, W)  Example of data using GENIII image intensified CCD  Meteoroids of mm size and mg mass (10 -6 kg).  Determine the bulk density  Infer the physical properties of the very small meteoroids and establish the link to the parent bodies.

Introduction  Background 1.Meteoroid, Meteor, Meteorite From Ceplecha, 1998 Peekskill meteor (Oct, 1992)

2.Origin: Asteroids Meteoroids: freed through collisions and fragmentations small eccentricity and low inclinations Asteroids: Between Mars (1.5 AU) and Jupiter (~5 AU) Asteroid belt: between 1.8 AU and 4.5 AU. Eros

Origin: Comets Meteoroids: freed through the processes of sublimation. JFC HTC and NIC HaleBoop Comet approaches the sun sunlight warms and sublimates ice. released gases drag dust from the surface large eccentricity and high inclination

Solar Nebula – Frost line ROCKY ROCKY-ICE comets High melting point compounds: metals (iron, nickel, aluminium) and rocky silicates (generally called refractory). High density building blocks Condensation of water, into ice grains. Low density building blocks  Is the separation strict?  Do we only find icy materials in JFComets?  Is bulk density of JFC meteoroid always low?  Is there large scale radial mixing?

STARDUST MISSION Encoutered the comet 81P/Wild 2 on January 2, 2004 at a distance of 236.4± 1 km. Brought back samples from JF comet 81P/Wild2

Major finding result of Stardust mission  Expected result: particles from the icy parts of the outer solar system, grains from the interstellar medium. Low bulk density.  What was found: dust altered by heating and other processes formed inner solar system (chondrules, CAIs found in meteorites: silicates and oxide minerals).  Implication: some transport of refractory dust from inner solar system to outer solar system. Ishii et al, 2006

 Motivation  Measure the bulk density of millimeter sized meteoroids.  Impact risk to artificial satellites  Understanding the physical structure and chemistry of meteoroid parent bodies  This is a difficult task (many attempts made last 50 years).To be successful, we need:  Precise observations to constrain a model of meteoroid ablation (Instruments)  A complete model of ablation (search the full parameter space)

Fundamental equations 1. Deceleration of the meteoroid Γ: drag coefficient (fraction of the momentum transferred to the body (from 0 to 2). A: shape factor ρ d : bulk density of the meteoroid ρ: air density m: meteoroid mass v: meteoroid velocity 2. Mass-loss equation: 3. Luminosity equation Λ: heat-tranfer coefficient (kinetic energy to ablate the body) (<=1) Q: heat of ablation(energy to melt or vaporise a mass dm. I: luminosity τ: kinetic energy lost by the meteoroid and turn to light production. SINGLE BODY THEORY

Meteor at Elginfield, London, Ontario Wide field (20º)Narrow field (1.5º) FRAGMENTATION (small meteors)

 Previous work  Single body theory (Bellot Rubio et al., 2002) oDynamical properties of the meteoroid o Deceleration  Fragmentation (Babadzhanov, 2002) o Mass loss equation oFitting solely the light curve From Bellot Rubio et al., 2002

 Our Goals: 1.Reconcile single body theory and fragmentation 2.Infer the physical properties of very small meteoroids.  A model of ablation to fit simultaneously the observed lightcurve and the observed deceleration of small meteoroids  Use orbits to link to their origin 73P/Schwassmann-Wachmann3 (Credit NASA, ESA)

Model of Ablation  Dustball model (Hawkes and Jones, 1975):  grains held together by a ‘glue’.  “glue” has low point of evaporation  Boiling point of the ‘glue’ reached  Release of grains into airstream (from the smaller ones to the bigger ones).

 Ablation Model (Campbell-Brown and Koschny, 2004): Model based on:  Thermal fragmentation (energy described by the change of temperature over time).  Momentum leading to the estimation of deceleration.  Mass loss takes into account all different processes of ablation ( spallation, radiation, evaporation).  Light production.

 Free parameters: 1)Mass (grain mass distribution follows power law) (total mass estimated from photometric mass. 2)Density (300 kg/m 3 – 8000 kg/m 3 ) 3)heat of ablation (1x10 6 J/kg – 9x10 6 J/kg), 4)boiling ‘glue’ temperature (1400K – 2300 K), 5)boiling grains temperature (800 K – 1500 K), 6)specific heat (800 J/kg K– 1800 J/kg K), 7)molar mass of the meteoroid (20 au – 56 au) 8)thermo-conductivity of the meteoroid (0.1 W/m K – 1 W/m K). Ranges used in the model span the spectrum from CI chondrites, IDPs, ordinary chondrites, iron meteorites.

mass grain distribution: (3 bins): e e e-09 Density: 950 kg/m3 Heat of ablation: 6.5x10^6 J/kg T_lim: 930 K T_boil: 1900 K Spec heat: 1400 J/Kg K Molar mass: 36 Thermal conduct: 0.5 W/m K mass grain distribution: (2 bins): e e-09 Density: 950 kg/m3 Heat of ablation: 7.0x10^6 J/kg T_lim: 1370 K T_boil: 2100 K Spec heat: 1500 J/Kg K Molar mass: 36 Thermal conduct: 0.2 W/m K

Instruments and data 1. Gen III  Fujinon 25mm f/0.85  Images: 640x480pixels  Field of view: 34.4x24.9 degrees.  Scale 0.05 deg/pixel. (3.1 arcmin/pixel).  At 100 km range, 1 pixel=94m.  30 frames per second  Limiting stellar magnitude: +9 Mag : Elginfied : Tavistock

2.Gated Camera  Fujinon 50mm f/0.95  Images: 1360x1036 pixels  FOV: 15.2x11.5 degrees.  Scale deg/pixel. (0.67 arcmin/pixel).  At 100 km range, 1 pixel = 20m.  CCD: 5 Hz, Gated: 200 Hz  Limiting stellar magnitude: +8.5 Mg : Brussels, Ontario

3. Cooke Camera  Fujinon 50mm f/0.95  Images: 1024x1024pixels  Field of view: 34.4x24.9 degrees.  Scale 0.02 deg/pixel. (1.2 arcmin/pixel).  At 100 km range, 1 pixel=35m.  20 frames per second  Limiting stellar magnitude: +9.3 Mag.

Data All data gathered with two (or three) stations between Total ~120 hours of observations 109 meteors captured 92 analyzed

Fit model to observations : Example data. meteor a.Lightcurve b.deceleration

Density: 950/-500/ Density: 975/-400/+300

Meteor

Density of suggests: long period highly inclined Saturated case: 480/-150/+250 kg/m 3 Corrected case: 970/-400/+200 kg/m 3 Fit model to observations: Solution “region”

Results: 92 meteors

Direct measurements (IDPs) Our work Love et al (IDPS) 150 (5 to 150 μm) stratospheric IDPs Density ranges from 300 to 6200 kg m -3 Denser IDPs contain large sulfide grains Three peaks: Around 1000 kg m -3 (cometary) Around 3000 kg m -3 (chondritic) Around 5000 kg m -3 (iron-rich)

Direct measurements (Meteorites) Carbonaceous chondrites 2200±50 kg/m 3 ~20% porosity Ordinary chondrites 3200 ± 20 kg/m 3 ~10% porosity Stony-iron meteorites 4500±40 kg/m 3 ~5 % porosity

Meteor spectra (Borovicka et al., 2005) 97 meteor spectra

 (SA) Sun-approaching orbits: q<0.2 AU  (ES): Ecliptic shower orbits: (low inclination meteor shower)  (HT): Halley type orbits (Tj 45º  (JF): Jupiter family orbits (2 4.5 AU  (A-C): Asteroidal-chondritic orbits: Tj>3 or Q<4.5 AU aj: Jupiter’s semi-major axis, a, e and i: semi-major axis, eccentricity and inclination of the body. Tisserand parameter: Classification: Borovicka et al. 2005

Borovicka et al orbit classifications Roughly:  3<Tj: asteroids (Main belt)  2<Tj<3: Jupiter Family comets (Kuiper belt)  Tj<2 : Halley type comets (Oort cloud)

2<Tj<3

AC Class Our work Borovicka et al., 2005 (x=iron meteoroids) Average density: 4200 kg/m3 RESULTS

HT Class  Range: 360/-100/+400 kg/m3 to 1510/- 900/+400 kg/m3  Perseids (10 meteoroids): average: 620 kg/m3 (HT origin)  4 meteoroids of NIA (Northern Iota Aquariids).  Average density: 3200 kg/m3 (Taurids origin, parent body: 2P/Encke). ES Class  Density spreads from 1000 kg/m 3 to 4000 kg/m 3.  Multiple origins SA class

JF class  We found ~ 80% of JFC meteoroids have density around 3000 kg/m 3  No system error only on JFC.

JF class  Average density: /- 300 kg/m 3  Very unexpected result!  High density for JFC meteoroids (more chondritic than cometary)  Stardust measurements of 81P/Wild2 reported the presence of refractory material.  Inclusion of refractory material common phenomenon among broader JFC population.

Conclusion I  Our model reconciles Bellot Rubio et al (2002) (low densities) and Babadzhanov (2002) (high densities).  Our measurements show meteoroid range in density from fluffy cometary density to chondritic density and “iron” density.  JFC meteoroids have density more chondritic than cometary in agreement with the results of the Stardust mission on 81P/Wild2 Jupiter family comet.  Our results show that inclusion of refractory materials is a common process among JFC comets.  Supports theories suggesting large scale radial transport in early solar nebula. Ishii et al. 2006

Three plausible interpretations: 1.Our JFC-like meteoroids are from JFCs and reflect their physical properties  JFC meteoroids have bulk density more chondritic than cometary in agreement with the results of the Stardust mission to the JFC 81P/Wild 2 2.Our JFC-like meteoroids are from JFCs but have been thermally sintered due to epochs with low-q  IDP collection of JFC material compromised 3.Our JFC-like meteoroids are from MB or NEA population  Explains agreement with asteroidal densities, but at variance with recent models (Nesvorny et al., 2010; Wiegert et al., 2010) which show JFCs dominant dust delivery to Earth  Our data show cometary density, chondritic density and “iron” density sorted into clear population groups. *See published paper: Kikwaya, Campbell-Brown, Brown, A&A, 2011, 530, A113 Conclusion II *