Investigation of Surface Chemistry from Electron Irradiation of Synthetic Schreibersite

Author

Tyler Davis, Kennesaw State UniversityFollow

Date of Award

Spring 4-24-2024

Degree Type

Thesis

Degree Name

Master of Science in Chemical Sciences

Department

Department of Chemistry and Biochemistry

Committee Chair/First Advisor

Heather Abbott-Lyon

Second Advisor

Martina Kaledin

Third Advisor

Bharat Baruah

Abstract

While phosphorus is one of the key elements for life on Earth, it has relatively low abundance in extraterrestrial environments, making it a target for astronomers and astrobiologists interested in the possibility of life beyond our planet. Schreibersite (Fe,Ni)₃P is one of the first P-containing minerals to condense during planetary cooling and one of the primary P-containing minerals in iron and stony-iron meteorites. Therefore, it is a likely P-bearing mineral in cometary cores and dust grains within the interstellar medium and circumstellar envelopes. Experiments in this project were performed with the aim of observing the formation of small P-containing molecules when ice-covered synthetic schreibersite is irradiated with electrons of varying energies (100-1000 eV). Surface science analysis was performed in an ultrahigh vacuum (UHV) chamber with the ability to mimic cometary conditions (T < 125 K, P < 1 x 10^-9 torr). The relative abundance of the most likely small P-bearing molecules in space including, PO, PN, CP, HCP, and PH₃, were searched for using surface-sensitive infrared spectroscopy and mass spectrometry. Formation of phosphorus-bearing compounds on the surface of the synthetic schreibersite sample was not observed in RAIRS data. Additionally, no mass-to-charge ratios believed to correspond to phosphorus-bearing compounds were seen in QMS desorption data. However, CO₂ formation on the surface was seen in RAIRS and QMS data during desorption. Our measurements constrain the conditions under which volatile phosphorus species are formed in the outer Solar System. Additionally, they impact our understanding of the phosphorus chemical cycle on icy planetary bodies (e.g., comets, Jovian and Saturnian moons) and the potential habitability of extraterrestrial environments.

Comments

Presented at 2023 SERMACS in Durham, NC

Winner of best poster at 2024 GA Academy of Sciences