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Meteorite paleomagnetism: Constraints on planetary migration and the formation of the first solids

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It is thought that there were at least two major planetary rearrangements within the first 1 Gyr of our solar system. Such events are believed to have played a crucial role in shaping the present-day architecture our solar system as well as possibly those of exoplanetary systems. Within our own solar system, these planetary migrations have been proposed to have brought material that formed beyond the orbit of the gas giants into the inner solar system, possibly explaining the compositional trends across the asteroid belt as well as the makeup of the Trojan asteroids. However, very few robust, accurate or quantitative estimates of the heliocentric distances of the formation of meteorite parent bodies exist. These distance estimates would also provide a means of investigating the range over which the first solids may have been recycled throughout the solar system. Here, we present paleomagnetic evidence that the Tagish Lake meteorite does not contain a stable magnetic remanence. Given the ancient aqueous alteration age of this meteorite (less than 4 Myr after calcium-aluminium rich [CAI] formation), this absence suggests that the Tagish Lake parent body must have originated from more than 10 – 20 AU where the magnetic field 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 orbits of the gas giants prior to Grand Tack, suggesting the Tagish Lake parent 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 the 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 Uranus within 3-4 Myr. Finally, our results provide the first direct, quantitative observation from the meteorite record that a body formed in the outer 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.

This talk is part of the Exoplanet Meetings series.

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