Is There Life on Mars?

Is there life on Mars? Few questions, scientific or otherwise, fire the public imagination as much as this one. From H.G. Wells to David Bowie, speculations about Martian life have been a pervasive part of popular culture. There is a good reason for this intense interest: Mars is our planetary next-door neighbor, is the most exciting and accessible field on which to look for alien life. Mars, like Earth, formed about 4.5 billion years ago. A flood of new data from NASA reveals that Mars, like Earth, once had an abundance of surface water, especially during the planet’s first billion years.

Mars once had lakes, underwater volcanic systems and a benign temperature and atmosphere that might have allowed the spark of life. Indeed, Mars was probably habitable long before Earth. Mars still has water beneath its cold dry surface. It’s possible that Martian microbial life still survives in protected pockets underground.

In spite of these fascinating possibilities, today scientists tend to be weary when asked “is there life on mars?” This question has a long history of fraud, a history that underscores the profound difficulty of recognizing life on the base of limited data.

The first serious proposals regarding life on Mars were fueled by telescope observations of the red planet’s surface. The Italian astronomer Giovanni Schiaparelli (1835-1910) first reported what appeared to be faint straight line markings on the Martian surface in 1887. He called these features “canali”, which is the Italian word for channels. This is a neutral word with no suggestion of their origin and said nothing regarding the question “is there life on mars”.

As it turned out, the canali were just optical illusions. The human brain tends to connect the dots between dark patched on a light background. Ironically, Schiaparelli’s descriptions were mistranslated into English as canals. That designation fired the imagination of the wealthy American astronomer Percival Lowell (1855-1916). He was born and educated in Boston. In 1894, he used part of the family fortune to build and operate the Lowell Observatory, principally to try to find life on mars.

By 1895, he reported his first observations of a network of canals on the red planet, what he interpreted as evidence of an advanced civilization. Three years later, he founded a journal that promoted the idea of an ancient intelligent civilization on the red planet. Such speculation inspired the imagination of science fiction writers. H.G. Wells’ novel “The War of the Worlds” was published in the year 1898.

Nevertheless, the scientific community was not convinced. In fact, claims like those of Lowell hardened the scientific community for generations against any proposals regarding life elsewhere in the universe.

NASA’s early Missions: Is There Life on Mars?

Fast forward to the 1960’s, NASA began its widely successful effort to probe nearby planets with robotic missions. Efforts such as the Mariner and Viking missions had a variety of goals: geology, geophysics, mineralogy and more. The search for life, however, was always a prime objective. Beginning in 1965 and continuing through the early 1970’s, NASA’s four Mariner spacecrafts flew close to Mars and produced thousands of remarkable images of a hostile, dry and desolate world. The surface of Mars was full of craters and immense volcanoes, much bigger than any volcanoes on Earth. They found no canals and no cities. Not even a hint of life-sustaining water was found.

Then, in 1976, the first of NASA’s Viking missions carried an array of experiments to the Martian surface. One key objective of this mission was to look for organic compounds in the search for evidence of cellular activity. The result of these experiments confounded the scientists. On the one hand, an experiment specifically designed to look for microbial activity yielded a positive signal. The so called “labeled release experiment” involved scooping up a small amount of Martian soil, exposing it to a nutrient rich solution that had been labeled with radioactive carbon atoms, and then watch for the release of radioactive carbon dioxide. That’s a sign of life.

Sure enough, the experiment produced a big radioactive signal. The nutrients had reacted vigorously with the soil, releasing radioactive carbon dioxide in what appeared to be a metabolic reaction. A second experiment designed to identify carbon-based molecules in the soil seemed to contradict the labeled release results. Viking’s organic analyzer found nothing at all, not even a trace of carbon-based molecules. This result was a mystery, because Mars, like Earth, is subjected to a steady rain of microscopic organic-rich particles from space. There should be at least a little carbon on the Martian surface, yet the experiment showed nothing.

That result seemed to rule out any possibility of living cells. How could there be microbes and no carbon? These ambiguous results have led to years of controversy. The majority of scientists say that the lack of organic molecules proves that there is no life on Mars. They explained the strong labeled release as a result of chemicals on the soil. According to this view, potent chemicals reacted with the nutrients and caused the release of radioactive carbon dioxide.

Others, however, are equally convinced that Viking did find life. According to them, the organic analyzer wasn’t sensitive enough.

The bottom line is that Viking didn’t answer the question “is there life on Mars?”. We have to go back and do more experiments. NASA is taking a very cautious and measured approach to avoid any more ambiguous results. I will talk about new evidences for life on Mars and recent efforts by NASA in my future articles. Stay tuned.

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