Marietta Blau was born in Vienna, on April 29, 1984, in a middle-class Jewish family, to Mayer, a court lawyer and music publisher, and his wife, Florentine Goldzweig.
From 1914 to 191, after having obtained the general certificate of education from the girls' high school run by the Association for the Extended Education of Women, she studied physics and mathematics at the University of Vienna.
After completing her doctorate in 1919 at the University of Vienna, she could not find any suitable research positions with income or status. She pursued her own research as an unpaid volunteer at the Institute for Radium Research in Vienna, where she performed groundbreaking research throughout much of the 1920s and 1930s. While at the Institute, she developed photographic nuclear emulsions, that was usefully able to image and accurately measure high-energy nuclear particles and events. Additionally, this established a method to accurately study reactions caused by cosmic ray events. Her nuclear emulsions significantly advanced the field of particle physics in her time.
From 1919 to 1923, Blau held several positions in industrial and University research institutions in Austria and Germany; in 1921, she moved to Berlin to work at a manufacturer of x-ray tubes, a position she left in order to become an assistant at the Institute for Medical Physics at the University of Frankfurt am Main. From 1923 on, she worked as an unpaid scientist at the Institute for Radium Research of the Austrian Academy of Sciences in Vienna. A stipend by the Austrian Association of University Women made it possible for her to do research also in Göttingen and Paris (1932/1933).
In her Vienna years, Blau's main interest was the development of the photographic method of particle detection. The methodical goals which she pursued were the identification of particles, in particular alpha-particles and protons, and the determination of their energy based on the characteristics of the tracks they left in emulsions; there, she developed a photographic emulsion technique used in the study of cosmic rays, being the first scientist use nuclear emulsions to detect neutrons.
For this work, Blau and her former student Hertha Wambacher received the Lieben Prize of the Austrian Academy of Sciences in 1937. It was her greatest success when, also in 1937, she and Wambacher discovered "disintegration stars" in photographic plates that had been exposed to cosmic radiation at an altitude of 2,300 metres (≈7,500 feet) above sea level. These stars are the patterns of particle tracks from nuclear reactions (spallation events) of cosmic-ray particles with nuclei of the photographic emulsion.
Because of her Jewish descent, Blau had to leave Austria in 1938 after the country's annexation by Nazi Germany, a fact which caused a severe break in her scientific career. She first went to Oslo. Then, through the intercession of Albert Einstein, she obtained a teaching position at the Instituto Politécnico Nacional in Mexico City and later at Universidad Michoacana de San Nicolás de Hidalgo.
Before she left Austria, her scientific papers were confiscated by German officials in Hamburg, some of which included plans for future research. Later on, some of the ideas were published by her former collaborator Wambacher and G. Stetter, both of who were supporters of the Nazi party. Blau spent a few years in Mexico before moving to the United States in 1944 to further her research.
In the United States, Blau worked in industry until 1948, afterward (until 1960) at Columbia University, Brookhaven National Laboratory, and the University of Miami. At these institutions, she was responsible for the application of the photographic method of particle detection in high-energy experiments at particle accelerators.
In 1950, Cecil Powell won the Nobel Prize for Physics for applications of the photographic method that Blau developed early in her career. Powell decided to make this his field of research once he had been alerted to Blau and Wambacher’s previous research of the topic. Blau was also nominated for the 1950 Nobel Prize due to her development of photographic nuclear emulsions but did not win.
In 1960, Blau returned to Austria and conducted scientific work at the Institute for Radium Research until 1964 – again without pay. She headed a working group analyzing particle-track photographs from experiments at CERN and supervised a dissertation in this field. In 1962, she received the Erwin Schrödinger Prize of the Austrian Academy of Sciences, but an attempt to make her also a corresponding member of the Academy was not successful.
Marietta Blau died in Vienna from cancer on January 27, 1970. Her illness was related to her unprotected handling of radioactive substances as well as her cigarette smoking over many years. No obituary appeared in any scientific publication.