Mars Revisited

At first, the data sent back to earth by two Mariner spacecraft more than 60 million miles away seemed to offer as little hope as the lunar rocks that life would be found elsewhere in the solar system. Flying past the planet Mars, the small, instrument-packed spacecraft detected no evidence of nitrogen, an indispensable ingredient of life on earth. Probing the upper reaches of the Martian atmosphere, they failed to find anything like the ozone shield that protects the earth's surface from the sun's deadly rain of ultraviolet radiation. Even their stunning close-up photographs from only 2,200 miles above the red planet seemed to indicate that Mars is a cold, cratered globe, altogether inhospitable to life as man knows it.

Or is it? At week's end the infra-red spectrometer on board Mariner 7, the second of the two vehicles that flew past Mars, detected two gases--ammonia and methane--that could indicate the presence of primitive life. Both are produced on earth by biological decay. George C. Pimentel, a University of California chemist, said that he was unable to determine the amount of ammonia in the Martian atmosphere, but he estimated the concentration of methane as "no more than a few parts per million." In the earth's atmosphere, the amount is about 1.5 p.p.m.--and added rather jovially that among the terrestrial sources of methane are marsh gas and bovine flatulence, both of which result from the gradual deterioration of vegetable matter.

Biological Origin. Pimentel conceded that the gases he detected might have been produced on Mars by such nonbiological processes as "outgassing" from Mars' interior. But, he added, "One cannot restrain the speculation that the gases might be of biological origin." If that is the case, he theorized, they may have been produced by organisms that found shelter in a relatively hospitable ( --94DEGF.) region near the edge of Mars' southern polar cap, where Mariner 7 concentrated its cameras and instruments. There, he said, they might have drawn water from the polar ice and protection from the sun's ultraviolet radiation under a cloud of carbon-dioxide particles.

Other scientists at Pasadena's Jet Propulsion Laboratory (JPL) hotly dispute the idea that the polar caps are largely frozen water. Most investigators are now convinced that they are mostly frozen carbon dioxide, otherwise known as dry ice. Mariner 7 helped their argument. Its infra-red radiometer measured the temperature of the area at -- 253DEGF., or roughly the frost point of carbon dioxide on Mars.

Even so, scientists are not quite ready to dismiss the possibility of life there altogether. Investigators think that microbes or other primitive forms of life may yet be discovered on Mars. In a number of studies, biologists have already shown that algae, plant seeds and even beetles can survive temperatures similar to those found on the red planet. "Considering the extreme conditions that organisms tolerate here on earth," adds the University of Hawaii's Sanford Siegel, a physiologist whose studies on low-temperature life have been supported by NASA, "I would be very surprised indeed if we didn't find life on other planets."

Puzzling Erosion. In all, Manner 7 radioed back 126 pictures, compared with 74 by Mariner 6, before speeding behind Mars en route to an orbit around the sun. The pictures have all but ended the old controversy about the so-called Martian canals. The "canals" are not distinct linear features laid out by intelligent beings, as some scientists once believed, but apparently rough, uneven splotches that lose their geometric-looking form on closer examination. Far from being the outpost of an advanced civilization, Mars more and more seems to be something of a primordial version of the earth, as it might have been billions of years ago. Says Caltech Geologist Robert Sharp: "We are looking at what could be baby pictures of the earth."

Clearly, the two highly successful Mariner flybys have whetted the appetites of space officials for further planetary exploration. NASA Administrator Thomas Paine last week urged the U.S. to send two nuclear-powered spaceships, one to serve as a rescue vehicle, on a two-year trip to Mars by the 1980s. Many scientists, noting that such a project would cost perhaps $60 billion, prefer less expensive unmanned probes beyond Mars. Last week 23 space scientists strongly urged "grand tours" of the outer planets in the mid-1970s. At that time, Jupiter, Saturn, Neptune, Uranus and Pluto will be so aligned that a spacecraft could sweep past at least three of them in a single, multibillion-mile journey. This rare planetary configuration, the panel noted, will not occur again for another 179 years.

This file is automatically generated by a robot program, so reader's discretion is required.