McKay, David Stewart

▪ 1997

      In 1996, a year in which extraterrestrials were the focus of movies, television shows, and books, David McKay proved that the real drama was taking place in a science laboratory. On August 7 McKay, leader of a NASA research team, announced that a 1.9-kg (4.2-lb) meteorite from Mars had yielded evidence indicating that primitive life may have existed on the planet. The news came only weeks after the 20th anniversary of the first Viking landing on Mars, which had concluded that the planet was sterile.

      McKay was born on Sept. 25, 1936, in Titusville, Pa. He earned a master's degree in geochemistry from the University of California, Berkeley, in 1960 and four years later received a Ph.D. in geology from Rice University, Houston, Texas. In 1965 he began working at the Manned Spacecraft Center (later Johnson Space Center), where he instructed Apollo astronauts in geology and analyzed soil samples they retrieved from the Moon. McKay worked on a variety of projects, including the development of a method for extracting oxygen and water from lunar materials that would enable people to live on the Moon. It was his work on ALH84001, the meteorite originally discovered in Antarctica in 1984, however, that placed the mild-mannered scientist in the spotlight.

      The meteorite, believed to be about 4.5 billion years old, had initially been classified as a diogenite, a common type of rock. It was not until 1994 that it was determined to be Martian. One of only 12 such known meteorites, the rock quickly attracted special interest. A research team was assembled with McKay as its leader. The study, which took more than two years, revealed several peculiarities. First was the presence of polycyclic aromatic hydrocarbons (PAHs). While these organic compounds are commonplace, found throughout the solar system, the PAHs in the meteorite were unusual in appearance, resembling the type that result from the decay of organic matter. The presence of the molecules within the rock and their absence on its surface ruled out Earth contamination. The team also discovered carbonate globules, which are closely associated with bacteria found on Earth. Moreover, iron sulfides and magnetite were present. These compounds, which are so small that one billion of them can fit on the head of a pin, do not usually coexist. Certain bacteria, however, synthesize them simultaneously.

      These discoveries, published by McKay and his co-workers in the journal Science, indicated the possibility of ancient life on Mars. While the news generated a flurry of debate, McKay stressed that the findings were not definitive proof and that further research was planned. (AMY TIKKANEN)

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