Detrital remanent magnetization in the solar nebula

Fu, R. R.; Weiss, B. P.

doi:10.1029/2011je003925

Cited by 23 publications

(25 citation statements)

References 80 publications

(144 reference statements)

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“…Finally, we consider collisions with other chondrules. Such collisions can impart large angular velocities to chondrules (110). The frequency of compound chondrules is 5%, which represents a lower bound to the frequency of collisions during cooling between approximately 1500 and 1100˚C (109,111).…”

Section: Calculation Of Paleointensitiesmentioning

confidence: 99%

Solar nebula magnetic fields recorded in the Semarkona meteorite

Weiss

Lima

et al. 2014

Science

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24 25 26Accepted Manuscript. This version has not undergone final editing. Please refer to the complete version of record at http://www.sciencemag.org/.2 Magnetic fields are proposed to have played a critical role in some of the most enigmatic 26 processes of planetary formation by mediating the rapid accretion of disk material onto the 27 central star and the formation of the first solids. However, there have been no direct 28 experimental constraints on these fields. Here we show that dusty olivine-bearing 29 chondrules from the Semarkona meteorite were magnetized in a nebular field of 54±21 µT. 30This intensity supports chondrule formation by nebular shocks or planetesimal collisions 31 rather than by electric currents, the x-wind, or other mechanisms near the sun. This 32 implies that background magnetic fields in the terrestrial planet-forming region were likely 33 5-54 µT, which is sufficient to account for measured rates of mass and angular momentum 34 transport in protoplanetary disks. 35 36Astronomical observations of young stellar objects indicate that early planetary systems 37 evolve through a protoplanetary disk phase in <5 million years (My) following the collapse of 38 their parent molecular clouds (1, 2). Disk evolution on such short timescales requires highly 39 efficient inward transport of mass accompanied by outward angular momentum transfer, which 40 allows disk material to accrete onto the central star while delivering angular momentum out of 41 the protoplanetary system. 42The mechanism of this rapid mass and angular momentum redistribution remains unknown. 43Several proposed processes invoke a central role for nebular magnetic fields. Among these, the 44 magnetorotational instability (MRI) and magnetic braking predict magnetic fields with intensities 45 of ~100 µT at 1 AU in the active layers of the disk (3, 4). Alternatively, transport by 46 magnetocentrifugal wind (MCW) requires large-scale, ordered magnetic fields stronger than ~10 47 µT at 1 AU. Finally, non-magnetic effects such as the baroclinic and Goldreich-Schubert-Fricke 48 instabilities may be the dominant mechanism of angular momentum transport in the absence of 49 sufficiently strong magnetic fields (5). Direct measurement of magnetic fields in the planet-50 forming regions of the disk can potentially distinguish among and constrain these hypothesized 51 mechanisms. 52Although current astronomical observations cannot directly measure magnetic fields in 53 planet-forming regions [(6); supplementary text], paleomagnetic experiments on meteoritic 54 materials can potentially constrain the strength of nebular magnetic fields. Chondrules are 55 millimeter-sized lithic constituents of primitive meteorites that formed in transient heating events 56 in the solar nebula. If a stable field was present during cooling, they should have acquired a 57 thermoremanent magnetization (TRM), which can be characterized via paleomagnetic 58 experiments. Besides assessing the role of magnetic fields in disk evolution, such paleomagnetic 59 measure...

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Section: Calculation Of Paleointensitiesmentioning

confidence: 99%

Solar nebula magnetic fields recorded in the Semarkona meteorite

Weiss

Lima

et al. 2014

Science

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153

216

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“…Up to 1% of the Fe content can be present as magnetite. Processes like accretional remanent magnetization (8) or detrital remanent magnetization (9) are possible candidates to form larger scale magnetic dust grains and cometesimals. These in turn allow the possibility for a comet to possess a larger scale remanent magnetic field.…”

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The nonmagnetic nucleus of comet 67P/Churyumov-Gerasimenko

Auster

Apáthy

Berghofer

et al. 2015

Science

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Knowledge of the magnetization of planetary bodies allows far--reaching conclusions on their formation processes, and the conditions in the solar nebular at that time. Based on magnetic field measurements during the descent and subsequent triple landing of the ROSETTA lander PHILAE on comet 67P/Churyumov--Gerasimenko, we show that no global magnetic field was detected within the limitations of analysis. The ROMAP suite of sensors measured an upper magnetic field magnitude of less than 2 nT at the cometary surface at multiple locations with the upper specific magnetic moment being < 3.1·•10 --5 Am 2 /kg for meter--size homogeneous magnetized boulders and the maximum dipole moment of 67P/Churyumov--Gerasimenko is 1.6·•10 8 Am 2 . We conclude that on this scale magnetic alignment in the pre--planetary nebular is of minor importance.One Sentence Summary: High--precision magnetic field measurements obtained during the triple landing of ROSETTA's lander PHILAE demonstrate that the Jupiter family comet 67P/Churyumov--Gerasimenko is unmagnetized (<3.1·•10 --5 A m 2 /kg).Main Text: Comets are believed to have been formed in the outer solar nebula beyond the snow line, where icy aggregates can grow in size to form larger bodies (1--3). Both the Kuiper belts as well as the Oort cloud are possible reservoirs of comets, with different processes leading to their formation (3). The dust--to--ice ratio of comets is of the order 1 (4, 5). Thus, a large fraction of cometary material is refractory material. Analysis of Stardust samples indicates a high contribution of Fe to this refractory material (6, 7). Up to 1% of the Fe content can be present as magnetite. Processes like accretional remanent magnetization (8) or detrital remanent magnetization (9) are possible candidates to form larger scale magnetic dust grains and cometesimals. These in turn allow the possibility for a comet to possess a larger scale remanent magnetic field.Detection of any cometary magnetization is difficult as a dipole field decreases with the cube of the distance from the object. Global magnetization of small solar system bodies can be detected either by spacecraft flybys or direct measurements on the surface. Whereas the flybys of the Galileo and Deep Space spacecraft at asteroids 951 Gaspra and 9969 Braille suggested the possibility of notable magnetization of these bodies (10,11), the distant flybys of the ROSETTA spacecraft (12) at asteroids 2867 Steins and 21 Lutetia provided an upper limit on the specific magnetic moment of 10 --6 Am 2 /kg (13, 14).Magnetic field measurements obtained during the flyby of the GIOTTO spacecraft at comet 1P/Halley offered an opportunity to estimate cometary magnetization as they revealed an almost magnetic field free (<50 pT) region around the nucleus (16,17). Taking into account the closest approach distance of 596 km to Halley's nucleus this corresponds to a formal dipole magnetic moment of < 5·•10 13 Am 2 or an upper specific magnetic moment of < 0.25 Am 2 /kg, an unreasonably large value indicating the l...

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“…Such discrete metal particles may have been accreted, along with chondrules, CAIs, etc., through magnetic interaction (Fu and Weiss, 2012). Considering the relatively small sizes of asteroids, the precursor metal particles may have been buried relatively deep in the asteroids (near the core region of asteroids?).…”

Section: Applications To Meteoriticsmentioning

confidence: 99%