Size‐selective Concentration of Chondrules and Other Small Particles in Protoplanetary Nebula Turbulence

Cuzzi, Jeffrey N.; Hogan, R. C.; Paque, J. M.; Dobrovolskis, Anthony R.

doi:10.1086/318233

Cited by 357 publications

(380 citation statements)

References 59 publications

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“…We simply mention that the absence of grains larger than about ∼1 cm in meteorites appears to be consistent with our finding that these would be captured preferentially in large embryos. Conversely, two features can explain the size distribution of chondrules in meteorites (see, in a different context Cuzzi et al 2001): grains smaller than centimeter-size are captured preferentially in small-planetesimals, and moreover, grains of smaller sizes are increasingly more difficult to capture, as a consequence of the hydrodynamical flow around these planetesimals.…”

Section: Discussionmentioning

confidence: 99%

On the filtering and processing of dust by planetesimals

Guillot

Ida

Ormel

2014

A&A

141

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Context. Circumstellar disks are known to contain a significant mass in dust ranging from micron to centimeter size. Meteorites are evidence that individual grains of those sizes were collected and assembled into planetesimals in the young solar system. Aims. We assess the efficiency of dust collection of a swarm of non-drifting planetesimals with radii ranging from 1 to 10 3 km and beyond. Methods. We calculate the collision probability of dust drifting in the disk due to gas drag by planetesimal accounting for several regimes depending on the size of the planetesimal, dust, and orbital distance: the geometric, Safronov, settling, and three-body regimes. We also include a hydrodynamical regime to account for the fact that small grains tend to be carried by the gas flow around planetesimals. Results. We provide expressions for the collision probability of dust by planetesimals and for the filtering efficiency by a swarm of planetesimals. For standard turbulence conditions (i.e., a turbulence parameter α = 10 −2 ), filtering is found to be inefficient, meaning that when crossing a minimum-mass solar nebula (MMSN) belt of planetesimals extending between 0.1 AU and 35 AU most dust particles are eventually accreted by the central star rather than colliding with planetesimals. However, if the disk is weakly turbulent (α = 10 −4 ) filtering becomes efficient in two regimes: (i) when planetesimals are all smaller than about 10 km in size, in which case collisions mostly take place in the geometric regime; and (ii) when planetary embryos larger than about 1000 km in size dominate the distribution, have a scale height smaller than one tenth of the gas scale height, and dust is of millimeter size or larger in which case most collisions take place in the settling regime. These two regimes have very different properties: we find that the local filtering efficiency x filter,MMSN scales with r −7/4 (where r is the orbital distance) in the geometric regime, but with r −1/4 to r 1/4 in the settling regime. This implies that the filtering of dust by small planetesimals should occur close to the central star and with a short spread in orbital distances. On the other hand, the filtering by embryos in the settling regime is expected to be more gradual and determined by the extent of the disk of embryos. Dust particles much smaller than millimeter size tend only to be captured by the smallest planetesimals because they otherwise move on gas streamlines and their collisions take place in the hydrodynamical regime. Conclusions. Our results hint at an inside-out formation of planetesimals in the infant solar system because small planetesimals in the geometrical limit can filter dust much more efficiently close to the central star. However, even a fully-formed belt of planetesimals such as the MMSN only marginally captures inward-drifting dust and this seems to imply that dust in the protosolar disk has been filtered by planetesimals even smaller than 1 km (not included in this study) or that it has been assembled into planetesi...

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Section: Discussionmentioning

confidence: 99%

On the filtering and processing of dust by planetesimals

Guillot

Ida

Ormel

2014

A&A

141

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“…In essence, this is exactly what our inference would be, based on the 146 Sm-142 Nd systematics, suggesting that the offset in the Sm/Nd ratio in terrestrial planets could be due to an accumulation of chondrules with a higher Sm/Nd. In practical terms, the calculated concentration of chondrules can increase by a factor of 10 with a high probability (Cuzzi et al 2001). Using the histogram shown in figure 8, this is enough to shift the 147 Sm/ 144 Nd from 0.1967 to 0.206.…”

Section: (B ) the Nd-isotope Composition Of The Terrestrial Planetsmentioning

confidence: 96%

“…Furthermore, modelling of turbulence in the solar nebula has also shown that the abundances of chondrules themselves could be enhanced by the process of turbulent concentration (Cuzzi et al 2001). More importantly, the prediction is that chondrules should be concentrated in the terrestrial planet regions (Cuzzi et al 1998), while porous aggregates would be concentrated in the outer planet regions.…”

Section: (B ) the Nd-isotope Composition Of The Terrestrial Planetsmentioning

confidence: 99%

Early differentiation of the Earth and the Moon

Bourdon

Touboul

Caro

et al. 2008

Phil. Trans. R. Soc. A.

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We examine the implications of new 182 W and 142 Nd data for Mars and the Moon for the early evolution of the Earth. The similarity of 182 W in the terrestrial and lunar mantles and their apparently differing Hf/W ratios indicate that the Moon-forming giant impact most probably took place more than 60 Ma after the formation of calcium-aluminium-rich inclusions (4.568 Gyr). This is not inconsistent with the apparent U-Pb age of the Earth. The new 142 Nd data for Martian meteorites show that Mars probably has a superchondritic Sm/Nd that could coincide with that of the Earth and the Moon. If this is interpreted by an early mantle differentiation event, this requires a buried enriched reservoir for the three objects. This is highly unlikely. For the Earth, we show, based on new mass-balance calculations for Nd isotopes, that the presence of a hidden reservoir is difficult to reconcile with the combined 142 Nd-143 Nd systematics of the Earth's mantle. We argue that a likely possibility is that the missing component was lost during or prior to accretion. Furthermore, the 142 Nd data for the Moon that were used to argue for the solidification of the magma ocean at ca 200 Myr are reinterpreted. Cumulate overturn, magma mixing and melting following lunar magma ocean crystallization at 50-100 Myr could have yielded the 200 Myr model age.

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“…Thus, the CV and CK groups characteristically contain large chondrules and refractory inclusions, whereas those in the CO and CM groups are significantly smaller. This important difference is currently regarded as being due to aerodynamic sorting in the solar nebula, and hence predates the onset of parent body processes (Cuzzi et al, 2001;Liffman, 2005). In contrast, it has been argued that the mineralogical and oxygen isotope variability among the CV, CM and CI groups is essentially the result of parent body alteration (Young et al, 1999).…”

Section: Carbonaceous Chondrites Typically Have Whole Rock Refractorymentioning

confidence: 99%

The relationship between CK and CV chondrites

Greenwood¹,

Franchi²,

Kearsley³

et al. 2010

Geochimica et Cosmochimica Acta

195

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CK chondrites are highly oxidized meteorites containing abundant magnetite and trace amounts of Fe,Ni-metal. Although the group is predominately composed of equilibrated meteorites (types 4 to 6), in recent years a significant number of new samples have been classified as being either CK3 or CK3-anomalous. These unequilibrated CKs often display a close affinity with members of the CV oxidized subgroup. CKs and CVs (oxidized subgroup) may therefore form a continuum and by implication could be derived from a single common parent body. To investigate the relationship between these two groups a detailed study of the oxygen isotope composition, opaque mineralogy and major and trace element geochemistry of a suite of CV and CK chondrites has been undertaken. The results of oxygen isotope analysis confirm the close affinity between CV and CK chondrites, while excluding the possibility of a linkage between the CO and CK groups. Magnetites in both CV and CK chondrites show significant compositional similarities, but high Ti contents are a diagnostic feature of the latter group. The results of major and trace element analysis demonstrate that both CV and CK chondrites show overlapping variation. Supporting evidence for a single common source for both groups comes from their similar cosmic-ray exposure age distributions. Recent reflectance spectral analysis is consistent with both the CVs and CKs being derived from Eos family asteroids, which are believed to have formed by the catastrophic disruption of a single large asteroid. Thus, a range of evidence appears to be consistent with CV and CK chondrites representing samples from a single thermally stratified parent body. In view of the close similarity between CV and CK chondrites some modification of the present classification scheme may be warranted, possibly involving integration of the two groups. One means of achieving this would be to reassigned CK chondrites to a subgroup of the oxidized CVs. It is recognized that a full evaluation of this proposal may require further study of the still poorly understood CK3 chondrites. ACCEPTED MANUSCRIPT3

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Size‐selective Concentration of Chondrules and Other Small Particles in Protoplanetary Nebula Turbulence

Cited by 357 publications

References 59 publications

On the filtering and processing of dust by planetesimals

On the filtering and processing of dust by planetesimals

Early differentiation of the Earth and the Moon

The relationship between CK and CV chondrites

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