Meteorite paleomagnetism: Constraints on the rearrangement of the planets and the formation of the first solids

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• James Bryson (Earth Sciences, Cambridge)
• Monday 23 October 2017, 14:00-15:00
• MR14, Centre for Mathematical Sciences, Wilberforce Road, Cambridge.

If you have a question about this talk, please contact Dr. Yufeng Lin.

It has been suggested 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, 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 constrain the range over which the first solids (chondrules and calcium-aluminium-rich inclusions [CAIs]) may have formed or have been recycled throughout the solar system by stellar outflows. 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 ( 10 – 20 AU where the magnetic field generated by the collapse of the dust and gas within the nebula was < 0.15 µT. This distance corresponds to radii greater than the orbits of the gas giants prior to the migrations involved in Grand Tack, suggesting the Tagish Lake parent body represents 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 stellar outflows were capable of transporting solid material that formed within 1 AU of the Sun and within 1 Myr of CAI formation to distances as far as that of present-day Saturn or Uranus. Finally, our results provide a 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 presence of major ancient planetary migrations that altered the architecture and structure of our solar system.

This talk is part of the DAMTP Astrophysics Seminars series.

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