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Mars Landing 1976

July 18, 2016

Planetary science has come a long way since the end of the 19th century. This month, the Juno spacecraft achieved orbit of Jupiter, just a year after the encounter of the New Horizons spacecraft with Pluto. New Horizons gave us the first detailed images of distant Pluto and its moons, and Juno will measure the composition of Jupiter, the largest planet in our Solar System, perhaps even discovering whether its clouds hide a rocky core.

Pluto, the ninth planet, was discovered by Clyde Tombaugh in 1930. Forty years before that, in 1890, Giovanni Schiaparelli (1835-1910) published his detailed map of the surface features of Mars (see figure). While unintended, Schiaparelli's map and the name given to the linear features he had seen launched a wave of speculation about Mars' being an inhabited planet.

Giovanni Schiaparelli, Atlas of Mars 1890

Giovanni Schiaparelli's 1890 map of Mars. This map is a composite of his observations over the years 1877 to 1886. (Via Wikimedia Commons.)


Schiaparelli used the Italian word, "canali," meaning "channels" in the sense of grooves, but the similarity of this word to the English word, "canals," prompted speculation that these were, indeed, Martian canals built by an intelligent race to channel water from the poles to oases that were also present on this map. As telescopes improved, such linear features were found to be just optical illusions caused by poor viewing conditions.

Before these features were shown to be false, they inspired Percival Lowell (1855-1916), a "one-percenter" of his time, to build an observatory, the Lowell Observatory, near Flagstaff, Arizona, a location ideal for observational astronomy because of its isolation, high altitude (6,900 feet), and mostly cloudless nights. Clyde Tombaugh discovered Pluto at the Lowell Observatory.

Lowell popularized his theories about Mars in three books: Mars, 1895, Mars and Its Canals, 1906, and Mars As the Abode of Life, 1908. By these books, Lowell popularized the idea that the Martian canals were built by an intelligent life form. He had many critics, one of whom was Alfred Russel Wallace (1823-1913), who deserves some of the credit for the theory of evolution by natural selection that's typically reserved for Charles Darwin. Wallace thought that Mars was too cold, too dry, and too airless for life.

A paragraph from page 153 of Mars by Percival Lowell.

A paragraph from page 153 of "Mars" by Percival Lowell. (Scan of my copy of a facsimile edition, published in 1978, of the 1895 original edition.)[1])


Such musing may have inspired Edgar Rice Burroughs to write his novels about an inhabited Mars, called "Barsoom" by the Martians. The plot development was assisted by the presence of a human, John Carter, a captain of the Confederacy during the American Civil War who was transported to Mars by some unknown process. The first novel of his Mars series was the 1917 A Princess of Mars.

Even during Lowell's lifetime, observational evidence was mounting that Mars was completely lacking in water. In mid-July, 1965, the Mariner 4 spacecraft showed us a cratered surface quite unlike the fanciful Mars of fiction. As an example of how far technology has progressed in recent years, the Mariner 4 images were actually stored on a mechanical tape recorder for transmission back to Earth at a necessarily slow data rate.

Mariner 4 image 10D, Memnonia Fossae

Mariner 4 image 10D, showing craters in the Memnonia Fossae region of Mars.

The image field is about 250 km x 250 km.

The crater section at the right is part of the crater, Dejnev, which is about 156 km in diameter.

(NASA image.)


Tourists would rather stop at roadside attractions and linger, rather than catch a fleeting glimpse as they pass quickly on the highway. Such is also true for planetary exploration, and the Mariner 4 fly-by was followed by an actual landing on Mars. The landing was by the Viking Lander 1 spacecraft on July 20, 1976, forty years ago.[2-4] At that landing, our image resolution of Mars improved at least a million-fold, going from a kilometer to millimeter specks of sand.

The Viking 1 lander's destination was Chryse Planitia. A twin lander, the Viking lander 2, arrived at Utopia Planitia a few weeks later, on September 3. Along with the landers were orbiters designed to image Mars at a much higher resolution than Mariner 4. Images were routinely snapped at 150-300 meter resolution, while selected areas were resolved down to 8 meters. They imaged the now familiar Martian landscape of huge canyons, volcanoes, and lava fields; and, of course, craters.

First Photograph Taken On Mars Surface (PIA00381)

First photograph taken on the surface of Mars. The photo was taken by the Viking lander 1. (NASA image.)


One interesting fact about the landers is the design of the footpads. Since so little was known about the surface of Mars at that time, it was feared than the Martian surface might be spongey, and the landers would sink into the surface.[2] For this reason, large area footpads were used. Martin Marietta, a predecessor to today's Lockheed Martin, designed a heatshield for entry into the Martian atmosphere composed of a cork-silica composite.[2] How the cork was sterilized to prevent contamination of the Martian biosphere is likely an interesting story in itself.

The landers were also designed to detect signs of life. As a cautionary tale, one of the life-detecting experiments registered a false-positive arising from the extreme oxidizing nature of the soil. It's believed that the intense solar ultraviolet radiation, present at the Martian surface because of its lack of a shielding atmosphere, forms oxidizing agents.

The Viking Lander 2 ceased functioning on April 11, 1980. The Viking Lander 1 held out a little longer, until November 11, 1982. Not surprisingly, events have been planned to commemorate the arrival at Mars of Viking Lander 1 forty years ago.[5]

First Color Image From Viking Lander 1 (PIA00563)

The first color image of Mars, acquired by the Viking Lander 1.

(NASA image.)


References:

  1. Percival Lowell, "Mars," Houghton Mifflin (Boston, 1895), 228 pages. Facsimile edition published in 1978 by History of Astronomy Reprints.
  2. Changing Knowledge of Mars Forever: Viking Lander Celebrates 40 Years of Success, Lockheed Martin, June 2016.
  3. A Viking history fact sheet, NASA Web Site (PDF file).
  4. Gallery of Viking images, NASA Web Site.
  5. Viking at 40 Events, NASA Web Site.                    

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