Regolith and Megaregolith Formation of H-Chondrites: Thermal Constraints on the Parent Body

Akridge, G.; Benoit, P. H.; Sears, D. W. G.

doi:10.1006/icar.1998.5904

Cited by 70 publications

(70 citation statements)

References 40 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In the thermal models of chondrite parent bodies which involve instantaneous accretion (Miyamoto et al 1981;Bennett and McSween 1995;Akridge et al 1998), the time at which peak temperature is realized decreases progressively from the center of the body outward (Fig. 8).…”

Section: Resultsmentioning

confidence: 99%

“…Although several heat sources for asteroids have been proposed (Wood and Pellas 1988), a growing consensus exists that the decay of 26 Al (a radionuclide with a short half-life of 0.72 Myr) and high decay energy provided the heat for melting and metamorphism (Huss et al 2001). Until now, heat transfer models have assumed, for ease of computation, that asteroid accretion was instantaneous, i.e., the asteroid attained its full size in an instant (e.g., Miyamoto et al 1981;Bennett and McSween 1995;Akridge et al 1998;Ghosh and McSween 1998). Instantaneous accretion models are based on the assumption that the accretion process does not have thermal consequences.…”

Section: Using Thermal Models To Link Accretion Models With Meteoritimentioning

confidence: 99%

See 1 more Smart Citation

Importance of the accretion process in asteroid thermal evolution: 6 Hebe as an example

Ghosh

Weidenschilling

McSween

2003

Meteorit & Planetary Scien

View full text Add to dashboard Cite

Importance of the accretion process in asteroid thermal evolution:6 Hebe as an example Abstract-Widespread evidence exists for heating that caused melting, thermal metamorphism, and aqueous alteration in meteorite parent bodies. Previous simulations of asteroid heat transfer have assumed that accretion was instantaneous. For the first time, we present a thermal model that assumes a realistic (incremental) accretion scenario and takes into account the heat budget produced by decay of 26 Al during the accretion process. By modeling 6 Hebe (assumed to be the H chondrite parent body), we show that, in contrast to results from instantaneous accretion models, an asteroid may reach its peak temperature during accretion, the time at which different depth zones within the asteroid attain peak metamorphic temperatures may increase from the center to the surface, and the volume of high-grade material in the interior may be significantly less than that of unmetamorphosed material surrounding the metamorphic core. We show that different times of initiation and duration of accretion produce a spectrum of evolutionary possibilities, and thereby, highlight the importance of the accretion process in shaping an asteroid's thermal history. Incremental accretion models provide a means of linking theoretical models of accretion to measurable quantities (peak temperatures, cooling rates, radioisotope closure times) in meteorites that were determined by their thermal histories.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Using Thermal Models To Link Accretion Models With Meteoritimentioning

confidence: 99%

Importance of the accretion process in asteroid thermal evolution: 6 Hebe as an example

Ghosh

Weidenschilling

McSween

2003

Meteorit & Planetary Scien

View full text Add to dashboard Cite

show abstract

“…Accordingly, several groups have developed a wide range of thermal models of planetesimals with short-lived radioactive nuclides (mainly 26 Al but also 60 Fe) as the main heat source (e.g., Miyamoto et al 1981;Miyamoto 1991;Grimm and McSween 1993;Bennett and McSween 1996;Akridge et al 1998;Merk et al 2002;Ghosh et al 2003;Tachibana & Huss 2003;Trieloff et al 2003;Bizzarro et al 2005;Baker et al 2005;Mostefaoui et al 2005;Hevey & Sanders 2006;Sahijpal et al 2007;Harrison & Grimm 2010;Elkins-Tanton et al 2011;Henke et al 2012aHenke et al , 2012bNeumann et al 2012;Monnereau et al 2013). In the context of ordinary chondrite parent bodies, such models predict an onion-shell structure (Trieloff et al 2003;Ghosh et al 2006;Henke et al 2012aHenke et al , 2012bHenke et al , 2013Wood 2003, and references therein), where all petrologic types formed on the same parent body with type 3 OCs being representative of the crust and type 6 OCs being representative of the core.…”

Section: Introductionmentioning

confidence: 99%

Multiple and Fast: The Accretion of Ordinary Chondrite Parent Bodies

Vernazza

Zanda

Binzel

et al. 2014

ApJ

125

View full text Add to dashboard Cite

Although petrologic, chemical, and isotopic studies of ordinary chondrites and meteorites in general have largely helped establish a chronology of the earliest events of planetesimal formation and their evolution, there are several questions that cannot be resolved via laboratory measurements and/or experiments alone. Here, we propose the rationale for several new constraints on the formation and evolution of ordinary chondrite parent bodies (and, by extension, most planetesimals) from newly available spectral measurements and mineralogical analysis of main-belt S-type asteroids (83 objects) and unequilibrated ordinary chondrite meteorites (53 samples). Based on the latter, we suggest that spectral data may be used to distinguish whether an ordinary chondrite was formed near the surface or in the interior of its parent body. If these constraints are correct, the suggested implications include that: (1) large groups of compositionally similar asteroids are a natural outcome of planetesimal formation and, consequently, meteorites within a given class can originate from multiple parent bodies; (2) the surfaces of large (up to ∼200 km) S-type main-belt asteroids mostly expose the interiors of the primordial bodies, a likely consequence of impacts by small asteroids (D < 10 km) in the early solar system; (3) the duration of accretion of the H chondrite parent bodies was likely short (instantaneous or in less than ∼10 5 yr, but certainly not as long as 1 Myr); (4) LL-like bodies formed closer to the Sun than H-like bodies, a possible consequence of the radial mixing and size sorting of chondrules in the protoplanetary disk prior to accretion.

show abstract

“…Apart from the models by Henke et al (2012) and Neumann et al (2012), who consider compaction of chondritic planetesimals as a thermally activated creep process (and possibly the calculations of Akridge et al 1997;Senshu 2006), most studies use the simplified parametrised approach based on Yomogida & Matsui (1984) and allow compaction in a rather small temperature window at ≈700 K (e.g. Akridge et al 1998;Hevey & Sanders 2006;Sahijpal et al 2007;Gupta & Sahijpal 2010) to study the insulating effect of regolith on the thermal evolution. Other studies which do not consider compaction explicitly, but discuss its effects on the results, still refer to some of the publications mentioned above (e.g.…”

Section: Introductionmentioning

confidence: 99%

Modelling of compaction in planetesimals

Neumann

Breuer

Spohn

2014

A&A

View full text Add to dashboard Cite

Aims. Compaction of initially porous material prior to melting is an important process that has influenced the interior structure and the thermal evolution of planetesimals in their early history. On the one hand, compaction decreases the porosity resulting in a reduction of the radius and on the other hand, the loss of porosity results in an increase of the thermal conductivity of the material and thus in a more efficient cooling. Porosity loss by hot pressing is the most efficient process of compaction in planetesimals and can be described by creep flow, which depends on temperature and stress. Hot pressing has been repeatedly modelled using a simplified approach, for which the porosity is gradually reduced in some fixed temperature interval between ≈650 K and 700 K. This approach neglects the dependence of compaction on stress and other factors such as matrix grain size and creep activation energy. In the present study, we compare this parametrised method with a self-consistent calculation of porosity loss via a creep related approach. Methods. We use our thermal evolution model from previous studies to model compaction of an initially porous body and consider four basic packings of spherical dust grains (simple cubic, orthorhombic, rhombohedral, and body-centred cubic). Depending on the grain packing, we calculate the effective stress and the associated porosity change via the thermally activated creep flow. For comparison, compaction is also modelled by simply reducing the initial porosity linearly to zero between 650 K and 700 K. As we are interested in thermal metamorphism and not melting, we only consider bodies that experience a maximum temperature below the solidus temperature of the metal phase. Results. For the creep related approach, the temperature interval in which compaction takes place depends strongly on the size of the planetesimal and is not fixed as assumed in the parametrised approach. Depending on the radius, the initial grain size, the activation energy, and the initial porosity and specific packing of the dust grains, the temperature interval lies within 500−1000 K. This finding implies that the parametrised approach strongly overestimates compaction and underestimates the maximum temperature. For the cases considered, the post-compaction porous layer retained at the surface is a factor of 1.5 to 4 thicker for the creep related approach. The difference in the temperature evolution between the two approaches increases with decreasing radius and the maximum temperature can deviate by over 30% for small bodies.

show abstract

Regolith and Megaregolith Formation of H-Chondrites: Thermal Constraints on the Parent Body

Cited by 70 publications

References 40 publications

Importance of the accretion process in asteroid thermal evolution: 6 Hebe as an example

Importance of the accretion process in asteroid thermal evolution: 6 Hebe as an example

Multiple and Fast: The Accretion of Ordinary Chondrite Parent Bodies

Modelling of compaction in planetesimals

Contact Info

Product

Resources

About