Electron Holography Details the Tagish Lake Parent Body and Implies Early Planetary Dynamics of the Solar System

The degree of aqueous alteration of small bodies in the solar system depends on the time of their formation, their size, and collisions with other bodies, among other factors. Therefore, a knowledge of the aqueous alterations recorded in meteorites is crucial to understanding the history of our solar system. The Tagish Lake meteorite, believed to have formed in the cold outer solar system, contains framboidal magnetite, a major product of the aqueous process. By in situ annealing experiments on the magnetic properties of the magnetite by electron holography and by numerical simulations, we show that the interior temperature of the parent body of the Tagish Lake meteorite reached ∼250°C as a result of radiogenic heating and an energetic impact. Our nanometer-scale magnetic study suggested that the parent body grew to >160 km in diameter in the Kuiper Belt at ∼3 Myr after the first solar system minerals formed and then experienced an energetic impact from a smaller body with a diameter of ∼10 km at a speed of ∼5 km s−1 about 4–5 Myr after the first minerals. The probability of such a high-impact-velocity event would have increased during travel of the parent body from the Kuiper Belt to the asteroid belt, triggered by the formation and migration of the giant planets. Our results imply the early dynamics of solar system bodies that occurred several million years after the formation of the solar system and a highly efficient formation of the outer bodies of the solar system, including Jupiter.