[MIS23-P03] Homogeneous nucleation of silicate nanoparticles in a microgravity environment using a sounding rocket
Keywords:Dust, Nucleation, Microgravity, Silicate
We conducted a set of microgravity nucleation experiments using a NASA Black Brant IX sounding rocket on October 7, 2019 to study the nucleation, growth and aggregation of silicate grains. Over a period of 460 seconds in microgravity silicate particles formed following the evaporation of starting materials previously deposited onto tantalum filaments that were resistively heated in six different experimental chambers. Particles formed via homogeneous nucleation from a supersaturated vapor after cooling in a buffer gas of either pure argon or a mixture of argon plus oxygen. The temperature and concentration of the evaporated vapor can be determined by direct imaging of a double-wavelength, Mach-Zehnder type interferometer. In addition, we successfully recovered both the payload and the particles produced during the experiment. We studied these analog presolar silicates using a transmission electron microscope. The particles have a size distribution centered at ~40 nm in diameter and are mostly amorphous but with some small degree of crystallinity in some grains. While some aggregated grains show clear boundaries between the particles, other samples show complete fusion with no observable boundaries remaining. We will discuss the nucleation of presolar grains based on the results of the further analyses of these experiments.