Norman Horowitz, a pioneer of the study of evolution through biochemical synthesis who conducted a search for life on Mars, died Wednesday at his home in Pasadena, Calif. He was 90.

In 1965, he began working with the Jet Propulsion Laboratory after showing interest in the biochemical evolution of life and its possible applications to the search for life on other worlds. He spent five years as chief of JPL’s bioscience section.

Horowitz was part of the scientific teams for both the Mariner and Viking missions to Mars. On the Viking mission, he and two collaborators designed an instrument capable of detecting any biochemical evidence of life on the planet.

The results of the experiment were negative at the two Viking sites, but the data continue to inform current efforts in astrobiology.

Horowitz may be best known for his 1945 thought experiment on biochemical evolution. The paper is considered the origin of the study of evolution at the molecular level.

He also performed an experiment that led to the widespread acceptance of the one-gene, one-enzyme hypothesis that, until the early 1950s, was considered a radical theory.

He was also the author of a 1986 book titled “To Utopia and Back: The Search for Life in the Solar System.”