Plausible parent bodies for enstatite chondrites and mesosiderites: Implications for Lutetia's fly-by

Vernazza, Pierre; Brunetto, R.; Binzel, Richard P.; Perron, C.; Fulvio, D.; Strazzulla, G.; Fulchignoni, M.

doi:10.1016/j.icarus.2009.03.016

Cited by 86 publications

(80 citation statements)

References 53 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…This appears to be consistent with spectral observations performed by the OSIRIS camera on Rosetta, which are indicative of spectral homogeneity across Steins' surface (Kueppers et al 2009). However, for E-type materials, space weathering is poorly understood and it is unclear whether it would significantly affect the spectral properties of the exposed material as it does for other taxonomic types, such as S-types (Vernazza et al 2009). Therefore, one cannot firmly conclude, based on this homogeneity, that the whole surface has been space weathered for the same amount of time, which would be the case in a scenario that starts from a nonporous monolithic structure.…”

Section: Resultsmentioning

confidence: 99%

A large crater as a probe of the internal structure of the E-type asteroid Steins

Jutzi

Michel²,

Benz

2010

A&A

View full text Add to dashboard Cite

Context. The detection of a large crater (2 km in diameter) on Steins, a diamond-shape asteroid with a diameter of only about 4.6 km, was a large surprise given the size of the asteroid itself. Steins belongs to the rare class of E-type asteroids, which had not been observed by any spacecraft before the Rosetta mission of the European Space Agency (ESA) in 2008. Aims. We demonstrate that this large crater places constraints on both the internal structure of Steins and its age based on crater counting. Methods. Numerical simulations of impacts were performed to reproduce the large crater, assuming four different initial internal structures of the asteroid: monolithic with or without microporosity, and rubble pile with or without microporosity. Results. To reproduce this crater, Steins must be either a rubble pile, which also contains microporosity, or a monolithic body with or without microporosity. The lack of porosity in meteorite analogues favors a structure without microporosity, which, according to our results, must have been monolothic. Moreover, the asteroid would be transformed into a rubble pile structure as a result of the crater formation, allowing it to be reshaped in its current shape by the YORP spin-up thermal effect. Conclusions. A combination of modeling and observations of surface features can thus serve as a probe of the internal structure of a small body and constrains its age estimate. Since the surface was totally refreshed when the large crater was formed, crater counting on Steins indicates the time that has passed since this impact event occurred.

show abstract

Section: Resultsmentioning

confidence: 99%

A large crater as a probe of the internal structure of the E-type asteroid Steins

Jutzi

Michel²,

Benz

2010

A&A

View full text Add to dashboard Cite

show abstract

“…Chapman & Salisbury (1973) first suggested that what we now term an M-type spectrum might be associated with enstatite chondrites (ECs) and Rivkin et al (2000) suggested a hydrated EC as a plausible composition for Lutetia. Recently, Vernazza et al (2009) and (partly) Nedelcu et al (2007) showed that ECs are a good match for the visible/near-infrared spectra of Lutetia. The measured visual albedo for Lutetia has typically ranged over 15-22%, much higher than for the more common (CI/CM) carbonaceous chondrites (CC) and overlapping the lower range for S-types (in recent literature, the early dedicated observations of Lutetia have been supplanted by reference to five rather inconsistent IRAS scans, which imply a still higher albedo and smaller effective diameter for Lutetia, well under 100 km, to which we assign less significance, especially because they are inconsistent with the mean size derived here).…”

Section: Taxonomy and Densitymentioning

confidence: 99%

Physical properties of the ESA Rosetta target asteroid (21) Lutetia

Drummond¹,

Conrad

Merline

et al. 2010

A&A

View full text Add to dashboard Cite

Context. Asteroid (21) Lutetia was the target of the ESA Rosetta mission flyby in 2010 July. Aims. We seek the best size estimates of the asteroid, the direction of its spin axis, and its bulk density, assuming its shape is well described by a smooth featureless triaxial ellipsoid. We also aim to evaluate the deviations from this assumption. Methods. We derive these quantities from the outlines of the asteroid in 307 images of its resolved apparent disk obtained with adaptive optics (AO) at Keck II and VLT, and combine these with recent mass determinations to estimate a bulk density. Results. Our best triaxial ellipsoid diameters for Lutetia, based on our AO images alone, are a × b × c = 132 × 101 × 93 km, with uncertainties of 4 × 3 × 13 km including estimated systematics, with a rotational pole within 5The AO model fit itself has internal precisions of 1 × 1 × 8 km, but it is evident both from this model derived from limited viewing aspects and the radius vector model given in a companion paper, that Lutetia significantly departs from an idealized ellipsoid. In particular, the long axis may be overestimated from the AO images alone by about 10 km. Therefore, we combine the best aspects of the radius vector and ellipsoid model into a hybrid ellipsoid model, as our final result, of diameters 124 ± 5 × 101 ± 4 × 93 ± 13 km that can be used to estimate volumes, sizes, and projected areas. The adopted pole position is withinConclusions. Using two separately determined masses and the volume of our hybrid model, we estimate a density of 3.5 ± 1.1 or 4.3 ± 0.8 g cm −3 . From the density evidence alone, we argue that this favors an enstatite-chondrite composition, although other compositions are formally allowed at the extremes (low-porosity CV/CO carbonaceous chondrite or high-porosity metallic). We discuss this in the context of other evidence.

show abstract

“…On the basis of spectral and polarimetric observations, three types of meteorites are generally taken into consideration as possible analogues: iron meteorites (Bowell et al 1978;Dollfus et al 1979), enstatite chondrites (Chapman et al 1975;Vernazza et al 2009), and some types of carbonaceous chondrites, mainly CO3 or CV3 (Belskaya & Lagerkvist 1996;Birlan et al 2004;Barucci et al 2008;Lazzarin et al 2009). The main problem in spectral data interpretation is the featureless spectrum of Lutetia.…”

Section: Introductionmentioning

confidence: 99%

Puzzling asteroid 21 Lutetia: our knowledge prior to the Rosetta fly-by

Belskaya

Fornasier

Krugly

et al. 2010

A&A

Self Cite

View full text Add to dashboard Cite

Aims. A wide observational campaign was carried out in [2004][2005][2006][2007][2008][2009] that aimed to complete the ground-based investigation of Lutetia prior to the Rosetta fly-by in July 2010. Methods. We obtained BVRI photometric and V-band polarimetric measurements over a wide range of phase angles, and visible and infrared spectra in the 0.4-2.4 μm range. We analyze them with previously published data to retrieve information about Lutetia's surface properties.Results. Values of lightcurve amplitudes, absolute magnitude, opposition effect, phase coefficient, and BVRI colors of Lutetia surface seen at near pole-on aspect are determined. We define more precisely parameters of polarization phase curve and show their distinct deviation from any other moderate-albedo asteroid. An indication of possible variations in both polarization and spectral data across the asteroid surface are found. To explain features found by different techniques, we propose that (i) Lutetia has a non-convex shape, probably due to a large crater, and heterogeneous surface properties probably related to surface morphology; (ii) at least part of the surface is covered by a fine-grained regolith of particle size smaller than 20 μm; (iii) the closest meteorite analogues of Lutetia's surface composition are particular types of carbonaceous chondrites, or Lutetia has specific surface composition that is not representative among studied meteorites.

show abstract

Plausible parent bodies for enstatite chondrites and mesosiderites: Implications for Lutetia's fly-by

Cited by 86 publications

References 53 publications

A large crater as a probe of the internal structure of the E-type asteroid Steins

A large crater as a probe of the internal structure of the E-type asteroid Steins

Physical properties of the ESA Rosetta target asteroid (21) Lutetia

Puzzling asteroid 21 Lutetia: our knowledge prior to the Rosetta fly-by

Contact Info

Product

Resources

About