Astrophysics with Radioactive Isotopes

Radioactive isotopes as tracers for the origin of micrometeorites

Not scheduled

20m

Oral Presentation

Speaker

Jenny Feige

Description

Solar system objects are constantly bombarded by solar and galactic cosmic-rays generating cosmogenic radioactive isotopes. The measurement of such isotopes in interplanetary dust particles (IDPs) provides an important step towards reconstructing the time they spent in space and hence, towards identifying the nature and origin of their parent bodies.
Generally, IDPs are produced from collisions or surface sublimation of Solar System objects (e.g., asteroids and comets). The solar radiation pressure causes the IDPs to slowly spiral towards our Sun. A fraction intercepts with Earth and lands on its surface as micrometeorites (MMs) – mostly submillimetre-sized spherical particles that were briefly melted during atmospheric entry.
We measured the $^{26}$Al and $^{10}$Be content of 12 MMs with sizes of 90-500 µm collected from urban areas, particularly from the rooftops of buildings, and from Antarctic sediments. These experimental results were compared to results from theoretical models providing cosmic-ray exposure ages and orbital evolutions. Applying these models, we tested different input parameters including 1) IDP diameters, compositions, and densities, 2) initial orbital parameters, 3) cosmic-ray flux profiles and 4) degrees of ablation during passage through the Earth’s atmosphere. Each of these parameters yielded different final $^{26}$Al and $^{10}$Be concentrations, which were compared to our experimental data for deducing the spatial origins of the MMs in our Solar System.
This initial study shows that our MMs potentially derive from within the Asteroid Belt up to the Kuiper Belt. However, for individual MMs multiple origins are possible. Hence, better statistics of radioactive isotopes within MMs may help to further constrain the sources of dust in our Solar System.