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SUMMARY:Meteorite paleomagnetism: Constraints on planetary migration and t
 he formation of the first solids - James Bryson (Cambridge)
DTSTART:20171101T160000Z
DTEND:20171101T170000Z
UID:TALK87861@talks.cam.ac.uk
CONTACT:Ed Gillen
DESCRIPTION:It is thought that there were at least two major planetary rea
 rrangements within the first 1 Gyr of our solar system. Such events are be
 lieved to have played a crucial role in shaping the present-day architectu
 re our solar system as well as possibly those of exoplanetary systems. Wit
 hin our own solar system\, these planetary migrations have been proposed t
 o have brought material that formed beyond the orbit of the gas giants int
 o the inner solar system\, possibly explaining the compositional trends ac
 ross the asteroid belt as well as the makeup of the Trojan asteroids. Howe
 ver\, very few robust\, accurate or quantitative estimates of the heliocen
 tric distances of the formation of meteorite parent bodies exist. These di
 stance estimates would also provide a means of investigating the range ove
 r which the first solids may have been recycled throughout the solar syste
 m. Here\, we present paleomagnetic evidence that the Tagish Lake meteorite
  does not contain a stable magnetic remanence. Given the ancient aqueous a
 lteration age of this meteorite (less than 4 Myr after calcium-aluminium r
 ich [CAI] formation)\, this absence suggests that the Tagish Lake parent b
 ody must have originated from more than 10 - 20 AU where the magnetic fiel
 d generated by the collapse of the dust and gas within the nebula was less
  than 0.15 micro-T. This distance corresponds to radii greater than the or
 bits of the gas giants prior to Grand Tack\, suggesting the Tagish Lake pa
 rent body represents the outer disk bodies that now constitute the Kuiper 
 belt and could therefore feasibly be a comet. Tagish Lake contains sparse 
 chondrules and even rare CAIs\, indicating that transport mechanisms in th
 e early solar system were capable of moving material that formed within 1 
 AU from the Sun to distances as far as that of present-day Saturn or Uranu
 s within 3-4 Myr. Finally\, our results provide the first direct\, quantit
 ative observation from the meteorite record that a body formed in the oute
 r solar system and now resides in the inner solar system\, supporting the 
 existence of major planetary migrations that altered the architecture and 
 structure of our solar system.
LOCATION:Martin Ryle Seminar Room\, Kavli Institute
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