Enstatite chondrite density, magnetic susceptibility, and porosity

Abstract-As part of a large-scale survey of meteorite bulk and grain densities, porosities, and magnetic susceptibilities, we measured these properties for 174 stones from 106 achondritic meteorites. These include four lunar meteorites, 15 stones from 10 shergottites, nakhlites, and chassignites (SNCs), 96 stones from 56 howardites, eucrites, and diogenites (HEDs), 17 stones from nine aubrites, two angrites, and 16 stones from 10 ureilites, four stones of three acapulcoites, as well as four stones of three lodranites, and 15 stones from eight primitive achondrites. Those meteorites derived from basalts and crustal material of differentiated parent bodies have lower densities and magnetic susceptibilities, on an average, than the more primitive achondrites, which have a higher percentage metal. A notable exception is the one chassignite in the study (Chassigny), which has a high grain density of 3.73 ± 0.04 g cm )3 . Ureilites have magnetic susceptibilities consistent with primitive achondrites, but lower grain densities. Porosities do not vary considerably between most of the groups, with most stones 5-14% porous, although on an average, ureilites and brachinites have lower porosities, with most stones less than 7% porous. For primitive achondrites, the higher metal content causes finds to exhibit weathering effects similar to what is observed in ordinary chondrites, with a reduction in grain density, magnetic susceptibility, and porosity as compared with unweathered falls. For lunites, SNCs, and HEDs, no such effect is observed. We also observe that grain density and magnetic susceptibility used in conjunction distinguish shergottites, nakhlites, and chassignites from each other. Shergottites and nakhlites have low grain densities (averaging 3.31 and 3.41 g cm )3 , respectively) whereas Chassigny is 3.7 g cm )3 . In magnetic susceptibility, shergottities and chassignites are similar (averaging 2.85 and 2.98 in log units of 10 )9 m 3 kg )1 , respectively) with nakhlites averaging higher at 3.42.

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“…4). In fact, its grain density and magnetic susceptibility are similar to those of EC finds (Macke et al. 2010).…”

Section: Resultssupporting

confidence: 73%

“…Physical properties of aubrites are not at all comparable to the same properties of ECs (Macke et al. 2010).…”

Section: Resultsmentioning

confidence: 94%

Density, porosity, and magnetic susceptibility of achondritic meteorites

Macke

Britt

Consolmagno

2011

Meteorit & Planetary Scien

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“…We note that the Blithfield EL6 chondrite fragment studied by Smith et al. (2006) has an unusually high bulk density of 3.93 g cm −3 compared with that obtained for two other Blithfield fragments (3.69 g cm −3 ; Macke et al. 2010).…”

Section: Discussionmentioning

confidence: 45%

“…2010). Blithfield has an unusually large variation in bulk and grain density (Macke et al. 2010), and so the departure of one fragment from the average may not be meaningful.…”

Section: Discussionmentioning

confidence: 99%

Determination of bulk density for small meteorite fragments via visible light 3‐D laser imaging

McCausland

Samson

McLeod

2011

Meteorit & Planetary Scien

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Abstract-Bulk density is an important intrinsic property of meteorites, but the necessary bulk volume measurement is difficult to do in a truly nondestructive way. Archimedean methods involving the displacement of a 40-100 lm beads ''fluid'' are commonly applied, but can encounter systematic errors. Herein, we report a visible light laser imaging technique for the nondestructive measurement of meteorite surface features, allowing for the subsequent assembly of 3-D volumetric models; the method is particularly applicable to small meteorite fragments and to fragile specimens. We have acquired laser image data for 24 fragments from 18 ordinary chondrites, carbonaceous chondrites, and achondrites, with masses ranging from 265.0 to 1.2 g. Laser imaging bulk density is consistent between sister fragments of meteorites down to sizes of about 0.5 cm 3 , an order of magnitude smaller than can be reliably measured with Archimedean beads techniques. Uncertainty is less than 2% for fragments >4 cm 3 , and typically between 2 and 4% for small fragments <4 cm 3 . For 10 fragments, 3-D laser imaging volumes are on average 1.3% smaller than those obtained with Archimedean beads. In a wider comparison using 21 meteorite fragments, 3-D laser imaging bulk densities are on average 2.14 ± 2.36% greater than the corresponding Archimedean method literature values for these meteorites. Difficulties in the procedure of 3-D image alignment may lead to a slight overestimation of meteorite bulk density, and so laser imaging-based bulk densities are maximum estimates that can be viewed as being complementary to the minimum bulk density estimates obtained using Archimedean beads methods.

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“…Average bulk densities (8,34) range from 2.96 to 3.03 g/cm 3 for CO and CV meteorites and 3.55 g/cm 3 for ECs. If Lutetia were composed purely of EC material, this would imply a bulk asteroid macroporosity of ~ 0 -13% (given the uncertainty range on Lutetia's density).…”

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confidence: 99%

Images of Asteroid 21 Lutetia: A Remnant Planetesimal from the Early Solar System

Sierks

Lamy

Barbieri

et al. 2011

Science

190

132

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Images obtained by the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) cameras onboard the Rosetta spacecraft reveal that asteroid 21 Lutetia has a complex geology and one of the highest asteroid densities measured so far, 3.4 ± 0.3 grams per cubic centimeter. The north pole region is covered by a thick layer of regolith, which is seen to flow in major landslides associated with albedo variation. Its geologically complex surface, ancient surface age, and high density suggest that Lutetia is most likely a primordial planetesimal. This contrasts with smaller asteroids visited by previous spacecraft, which are probably shattered bodies, fragments of larger parents, or reaccumulated rubble piles

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Enstatite chondrite density, magnetic susceptibility, and porosity

Cited by 54 publications

References 34 publications

Density, porosity, and magnetic susceptibility of achondritic meteorites

Density, porosity, and magnetic susceptibility of achondritic meteorites

Determination of bulk density for small meteorite fragments via visible light 3‐D laser imaging

Images of Asteroid 21 Lutetia: A Remnant Planetesimal from the Early Solar System

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