Astronomy: Marsh Gas on Mars

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Many a scientist's fond hope that there was life on Mars was dashed in 1963 when spectrographic studies revealed that the Martian atmosphere is as much as 50 times thinner than the earth's. It seemed almost certain that a relatively weak Martian gravity had allowed most of the planet's primitive atmosphere to leak off into space. There appeared to be practically no possibility that any of the lightest element, hydrogen, or its compounds, had remained long enough to play their essential role in the early evolution of life. Now it appears that such pessimism may have been unfounded. The newest studies of the Martian atmosphere indicate that it abounds in hydrogen compounds, some of which are similar to those produced by terrestrial organisms.

In a paper presented to an American Chemical Society meeting in San Francisco, Jet Propulsion Laboratory Astrophysicist Lewis Kaplan disclosed that spectrograms of the Martian atmosphere, made when the planet was 70 million miles from the earth last year, suggest that Mars has a concentration of hydrogen compounds in its atmosphere 1,000 times greater than the earth's. Those compounds probably include methane derivatives and possibly methane itself—a finding that could be significant because methane, or "marsh gas,"* is produced on earth by anaerobic bacteria, which do not require oxygen to exist. Even if the Martian methane is not produced by living organisms, Kaplan says, its presence along with other hydrocarbons detected in the spectrograms strongly suggests the existence of free hydrogen and a chemical environment from which life could evolve.

Strenuous Climate. Kaplan's discovery was made possible by French Astronomers Pierre and Janine Connes, who developed new equipment at the Observatoire de Haute-Provence that enabled them to produce the most detailed spectrograms of Mars ever made. Originally intended to reveal data about atmospheric pressure at the Martian surface, the spectrograms were of such high quality that they revealed unexpected absorption lines which had been indistinguishable in spectrograms recorded by less sensitive instruments. After careful analysis, Kaplan concluded that many of the absorption lines could have been caused only by reflected sunlight passing through hydrogen compounds in the Martian atmosphere.

The discovery of methanelike compounds on Mars, Kaplan believes, leaves only one important obstacle to life on the red planet: the apparent lack of water in liquid form. What little Martian water there is exists as polar-cap frost or vapor in the atmosphere; there are no oceans or even lakes similar to those in which the first terrestrial life evolved. "It would be a strenuous climate for life," says Kaplan, "but then not all life—even on earth—requires liquid water."

Convincing Picture. Scientists may soon be able to talk about Mars with more certainty. Astronomers Pierre and Janine Connes have now improved their instruments. They hope to make new and better spectrograms next year when Mars passes within 60 million miles of the earth. When these are available, says Kaplan, "I think we can speculate more reasonably about the possibility of life on Mars."