Norman Horowitz (geneticist)
Norman Harold Horowitz was a geneticist at Caltech
California Institute of Technology
The California Institute of Technology is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering...

 who achieved national fame as the scientist who devised experiments to determine whether life might exist
Viking biological experiments
The two Viking spacecraft each carried four types of biological experiments to the surface of Mars in the late 1970s. These were the first Mars landers to carry out experiments to look for biosignatures of life on Mars. The landers used a robotic arm to put soil samples into sealed test containers...

 on Mars
Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...

. His experiments were carried out by the Viking Lander of 1976, the first U.S. mission to successfully land an unmanned probe on the surface of Mars.

Horowitz was a member of both the National Academy of Sciences
United States National Academy of Sciences
The National Academy of Sciences is a corporation in the United States whose members serve pro bono as "advisers to the nation on science, engineering, and medicine." As a national academy, new members of the organization are elected annually by current members, based on their distinguished and...

 and the American Academy of Arts and Sciences
American Academy of Arts and Sciences
The American Academy of Arts and Sciences is an independent policy research center that conducts multidisciplinary studies of complex and emerging problems. The Academy’s elected members are leaders in the academic disciplines, the arts, business, and public affairs.James Bowdoin, John Adams, and...

. In 1965 he began work with the Jet Propulsion Laboratory
Jet Propulsion Laboratory
Jet Propulsion Laboratory is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. The facility is headquartered in the city of Pasadena on the border of La Cañada Flintridge and Pasadena...

 in Pasadena
Pasadena, California
Pasadena is a city in Los Angeles County, California, United States. Although famous for hosting the annual Rose Bowl football game and Tournament of Roses Parade, Pasadena is the home to many scientific and cultural institutions, including the California Institute of Technology , the Jet...

, serving for five years as chief of JPL’s bioscience section and as a member of the science teams for the Mariner and Viking
Viking program
The Viking program consisted of a pair of American space probes sent to Mars, Viking 1 and Viking 2. Each spacecraft was composed of two main parts, an orbiter designed to photograph the surface of Mars from orbit, and a lander designed to study the planet from the surface...

 missions to Mars. From 1977 to 1980, he was chairman of the biology division at Caltech.

Among advocates of space exploration, he was noted for his opposition to a space program centered on the use of human astronauts. Charlene Anderson recalls, "In personal discussions, he could be particularly vociferous on the topic of human versus robotic exploration. Norm argued that human exploration could only interfere with scientific exploration and confuse the public as to why we should explore space. In his view, science should drive the endeavor, not a lust for adventure."

Scientific career

Horowitz earned his BS
Bachelor of Science
A Bachelor of Science is an undergraduate academic degree awarded for completed courses that generally last three to five years .-Australia:In Australia, the BSc is a 3 year degree, offered from 1st year on...

 in biology at the University of Pittsburgh
University of Pittsburgh
The University of Pittsburgh, commonly referred to as Pitt, is a state-related research university located in Pittsburgh, Pennsylvania, United States. Founded as Pittsburgh Academy in 1787 on what was then the American frontier, Pitt is one of the oldest continuously chartered institutions of...

 in 1936 where his experience conducting research as an undergraduate help to persuade him to pursue further graduate training in science. He later established the endowed Norman H. Horowitz Fellowship at the University of Pittsburgh to support undergraduate research. He completed his PhD at Caltech in 1939 under embryologist Albert Tyler
Albert Tyler (biologist)
Albert Tyler was an American biologist whose research was focused on reproductive biology and development in marine organisms....

, and then became a postdoctoral researcher at Stanford University
Stanford University
The Leland Stanford Junior University, commonly referred to as Stanford University or Stanford, is a private research university on an campus located near Palo Alto, California. It is situated in the northwestern Santa Clara Valley on the San Francisco Peninsula, approximately northwest of San...

 in the laboratory of George W. Beadle. Horowitz returned to Caltech as a faculty member in 1946 and stayed at the Institute for the remainder of his career. He served as chair of the Biology Division from 1977 to 1980, and became professor emeritus in 1982.

As a scientist, Horowitz is best known for his discovery and demonstration in 1944 that a metabolic pathway is a series of steps, each catalyzed by a single enzyme. Working with Neurospora crassa
Neurospora crassa
Neurospora crassa is a type of red bread mold of the phylum Ascomycota. The genus name, meaning "nerve spore" refers to the characteristic striations on the spores. The first published account of this fungus was from an infestation of French bakeries in 1843. N...

, Horowitz demonstrated that each step in the metabolism of arginine
Arginine is an α-amino acid. The L-form is one of the 20 most common natural amino acids. At the level of molecular genetics, in the structure of the messenger ribonucleic acid mRNA, CGU, CGC, CGA, CGG, AGA, and AGG, are the triplets of nucleotide bases or codons that codify for arginine during...

 from its precursors depends on the intactness of a single gene. His discovery helped to clinch the case for George Beadle and Edward Tatum's "one gene-one enzyme hypothesis
One gene-one enzyme hypothesis
The one gene-one enzyme hypothesis is the idea that genes act through the production of enzymes, with each gene responsible for producing a single enzyme that in turn affects a single step in a metabolic pathway...

" (a term Horowitz coined for their concept).

Horowitz was head of the Pyrolytic Release experiment during the Viking program
Viking program
The Viking program consisted of a pair of American space probes sent to Mars, Viking 1 and Viking 2. Each spacecraft was composed of two main parts, an orbiter designed to photograph the surface of Mars from orbit, and a lander designed to study the planet from the surface...



  • Anderson, Charlene. In Memoriam: Norman Horowitz (1915-2005) The Planetary Society.
  • Horowitz, Norman H. "On the evolution of biochemical syntheses." Proceedings of the National Academy of Sciences 31 (1945) 153–157.
  • Horowitz, Norman H. To Utopia and Back: The Search for Life in the Solar System. (New York: W. H. Freeman) 1986.
  • Horowitz, Norman H. "Man on Mars: a turnabout." Science 238: 10. 1987.
  • Metzenberg, Robert L. "Norman Harold Horowitz, 1915–2005." Genetics. Dec 2005 171(4): 1445–1448.
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