Sandra Pizzarello, chemist and emeritus professor at Arizona State University, passed away on October 24, 2021. Pizzarello greatly enhanced the research field of molecular, isotopic, and chiral analysis of organic compounds in carbonaceous chondrite meteorites since the 1970s. During her active research career, she produced an impressive number of achievements in her studies on the origin and chemical evolution of organic compounds in the early solar system and the origin of homochirality in living systems.

Pizzarello was born in Venice, Italy, in 1933. She obtained a doctoral degree in Biological Sciences at Universitá degli Studi di Padova, Italy, in 1955. She was a research associate with Farmitalia Research Laboratories, Neuropharmacology Department, Milan, Italy, from 1957 to 1960. She joined the research staff at the Department of Chemistry and Biochemistry at Arizona State University (ASU) in 1977, where she remained a research professor and an emeritus professor until her death.

Pizzarello was a pioneering scientist who either identified or greatly expanded our knowledge of a suite of soluble compounds in carbonaceous chondrites such as amino acids, monocarboxylic acids, dicarboxylic acids, hydroxyl acids, hydroxydicarboxylic acids, aliphatic hydrocarbons, ammonia, amines, and polar hydrocarbons as well as insoluble organic matter (IOM). Together with the late Professor John R. Cronin, Pizzarello concentrated her efforts over 30 years on the development of the analytical techniques for these compounds — in particular, a diverse suite of over 80 amino acids, which is clearly different from the distributions of terrestrial amino acids. Pizzarello and Cronin carried out the first isotopic analysis of amino acids in meteorites and revealed enrichments in deuterium, carbon-13, and nitrogen-15. These results provided the first evidence suggesting a direct relationship between meteoritic organic compounds and interstellar chemistry. Later, Pizzarello worked on the compound-specific carbon, hydrogen, and nitrogen isotopic analyses of soluble organic compounds in meteorites. Her results demonstrated the diverse synthetic pathways of these compounds in the early solar system.

One of the most laudable achievements in Pizzarello’s work in collaboration with Cronin was their discovery of L-enantiomeric excesses (ee) in a suite of rare (non-biological) extraterrestrial amino acids from carbonaceous chondrites in 1997. Observing ee in non-biological compounds was definitive evidence that ee were present in the early solar system. The origin of the amino acid homochirality of life has been one of the most significant, unsolved questions in natural science, and their pioneering discovery established a strong position in the search for the origin of amino acid homochirality of life in the universe. Moreover, she experimentally showed that ee are catalytically transferred from amino acids when sugars are synthesized from the formose reaction. The result suggested that meteoritic amino acids could have provided the symmetry breaking necessary for the evolution of RNA by acting as catalysts of asymmetric syntheses leading to D-sugars. Her extensive works demonstrated the possible universality of molecular asymmetry in the universe, suggesting abiotic origins of biomolecular homochirality.

Pizzarello’s significant contributions to meteoritics, astronomy, astrobiology, and the origins of life have influenced the next generation of scientists in these research fields. She served as president of the International Society for the Study of the Origin of Life (ISSOL) — the international Astrobiology society — from 2014 to 2017, and was an effective mentor for younger scientists and a role model for women in science.

— Portions of text courtesy of The Meteorological Society
(H. Yabuta, G. Cooper, L. Williams, K. Soai, M. Bose)