Dust in the Solar System: Where Does it Come From?

Synopsis

Micrometeorites (MMs) are small particles of cosmic dust (with diameters between 30 micrometers and one millimeter) which have fallen onto Earth’s surface. When MMs are found on Earth, it is natural to ask where in the Solar System they have come from. In this talk, I will discuss an analysis performed by Feige et al.¹ to determine the origin of MMs found in urban locations and Antarctica. The study relies on the idea that, during travel, MMs are irradiated by Solar Cosmic Rays, which produce Al-26, and Galactic Cosmic Rays, which produce Be-10. I will give an overview of Accelerator Mass Spectrometry, which can be used to measure isotope populations of Be-10 and Al-26 in MMs. Additionally, I will describe a model used for simulating the evolution of Be-10 and Al-26 populations as the MM travels through the Solar System. This model is compared to the measured Be-10 and Al-26 to determine a likely spatial origin for the MMs. The work I will describe demonstrates how experimental nuclear physics and theoretical astronomy can be synthesized to learn about dust transport in the Solar System. We will also learn how dust can originate as far as the outer Solar system, so we don’t need to look much further than our own backyard (literally!) to find a variety of extraterrestrial samples.

¹Feige J et al. 2024 Transport of dust across the Solar System: Constraints on the spatial origin of individual micrometeorites from cosmic-ray exposure. Phil. Trans. R. Soc. A 382: 20230197.