## The Face on Mars

### Looking for patterns: The Man on the Moon

If you go out tonight and look up at the full Moon, and you're like most people, you'll probably see the face of a man, or, alternatively, a rabbit superimposed on the bright disk of the Moon. Yet if you were to look through even a small telescope at the full Moon, or at a photograph of it, you probably wouldn't see either thing. Why is that? The human tendency to see familiar shapes in random patterns of light and dark no doubt comes into play, especially given the blurring effects of turbulence in the Earth's atmosphere. Telescopic images and photographs contain enough sharp detail that your mind no longer needs to try to make sense out of the random patterns it sees by looking for familiar shapes.

Have your students make sketches of the full Moon while they are at home. Ask them to draw something like a first impression, a quick sketch that focuses mainly on the outlines of the dark maria, or lava plains on the lunar surface. Compare the sketches with a photograph of the Moon. Discuss what the sketches look like. How many look like a rabbit? How many like the Man in the Moon? How many like something else? Finally discuss whether there really is a rabbit or a giant face on the Moon.
 When people look at the full Moon, they often see either a Man in the Moon (left) or a rabbit in the Moon (right). (Courtesy American Museum of Natural History)

### Faces, Faces Everywhere

The Face on Mars is a naturally occurring rock outcropping that just happens to look like a face when lit from the side. Where else can you see naturally occurring objects that look like a face? Show your students pictures of clouds, tree bark, rock formations, or any other picture with a fairly complex structure to it, and have them look for faces or shapes of different animals in them. See how many different faces or animals students can find in the same picture. Also notice how once one student points out a face or animal, it is sometimes hard to see any other shape. You can also have the students draw a page of random, squiggly lines. Then have them see how little (or how much) it takes to turn parts of the "squiggles'' into recognizable shapes.

## Bibliography

• "The Man in the Moon,'' Carl Sagan, Parade June 2, 1985, page 12.
• "Facing Up to Mars,'' Frederic Golden, Discover, April 1985, page 92.
• "Seeing Faces on Mars,'' David Morrison, The Skeptical Inquirer, Fall 1988, page 76.
• ''The Great Stone Face and Other Nonmysteries,'' Martin Gardner, The Skeptical Inquirer, Fall 1985, page 14.
• ''Face-off,'' Alex Heard, Air and Space, June/July 1991, page 22.
• "The Face on Mars,'' Odyssey, October 1991, page 12.
• "Wishful Seeing,'' Jon Muller, The Skeptical Inquirer, Spring 1987, page 296.

## What Happened to Mars Observer?

On Saturday, August 21, 1993, NASA mission controllers lost contact with the Mars Observer spacecraft, one day before it was to enter orbit around Mars and begin a three-year mission to survey and study the Red Planet. Communication was lost after ground controllers had radioed commands to pressurize its fuel tanks in preparation of rocket firings to slow the spacecraft down and allow it to be captured by Mars' gravity.

Initially there was speculation that a problem with the pressurization may have caused the fuel to leak, making the spacecraft tumble out of control, or even explode. After a few days of silence, a second theory emerged: a pair of electronic transistors in Mars Observer's master clock, the timekeeper for most of the craft's computers, may have failed, disabling the spacecraft. Researchers found a similar problem in the master clock of the NOAA-3 weather satellite before its launch last June. The faulty transistors were from the same manufacturing batch as those aboard Mars Observer. The transistors on the weather satellite were replaced before launch, but Mars Observer was already on its way to Mars when the problem was discovered. A NASA task force investigating the cause of the loss of Mars Observer should release its findings around Thanksgiving of this year.

What about other missions to Mars? The Mars Environmental Survey (MESUR) will include a network of a dozen or more landers. Each lander will have a small mobile robot to explore the Martian surface. The first lander in the network, MESUR Pathfinder, is scheduled for launch by NASA in 1996 (to arrive at Mars in 1997). The MESURmissions are not dependent on results from Mars Observer, and thus should not be effected by its loss.

On the other hand, two planned Russian missions to Mars, Mars 94 and Mars 96, had hoped to use the Mars Observer orbiter to relay data from a Russian lander (in the case of Mars 94) and atmospheric balloon (for Mars 96) to their orbiters farther away from the planet. At this time it is unclear what effect the loss of Mars Observer will have on these missions. NASA scientists are also looking into the possibility of creating a new spacecraft to replace Mars Observer, using parts scavenged from other missions. But this replacement won't be ready until November 1996, at the earliest.

## Viking's Search for Life

On July 20, 1976, exactly seven years after the first manned landing on the Moon, the robotic Viking 1 lander safely touched down on the surface of Mars in a plain called Chryse. Two months later, a sister ship, Viking 2, also landed in a plain called Utopia. The two landers took thousands of pictures of the Martian surface and relayed millions of weather reports back to Earth.

The landers also carried miniature biological laboratories designed to perform three different tests for microorganisms in the Martian soil. The three tests were all based on the idea that living things alter their environment -- they eat, breathe, and give off waste products. In each test, the lander's long robotic arm scooped up some soil and put it in a closed container, with or without certain nutrients. The containers were then analyzed for changes in their contents, changes that could be attributed to biological processes. The three experiments were as follows:

• The gas-exchange experiment looked for evidence of what could broadly be called "respiration.'' The soil sample was placed into the container along with a controlled amount of gas and nutrients. Gases in the container were then monitored for any changes in their chemical composition.
• The labeled-release experiment looked for evidence of "metabolism.'' The soil sample was moistened with nutrients containing radioactive carbon atoms. Any organisms in the soil that "ate'' the carbon would give off gases containing radioactive carbon, which would be detected.
• The pyrolytic-release experiment looked for evidence of photosynthesis, the process by which plants on Earth convert carbon dioxide gas into organic compounds, using sunlight as an energy source. The soil sample was placed in a container with radioactive carbon dioxide gas and exposed to an artificial light source. If photosynthesis occurred, some of the radioactive carbon would be incorporated into microorganisms in the soil.
A fourth instrument pulverized the soil to look for traces of organic matter.

In almost every case, rapid and extensive changes took place within the experimental containers. But later analyses showed that the activity could have been caused by ordinary chemical, not biological, reactions. It appears that Martian soil is much more chemically active than soil on Earth, perhaps because of its exposure to the Sun's ultraviolet radiation (due to the lack of a protective ozone layer in the Martian atmosphere). The organic experiment found no trace whatsoever of organic material, which was apparently killed by this same ultraviolet light.

The Viking experiments were sensitive enough that they would have easily detected signs of life anywhere on Earth, with the possible exception of Antarctica. While the possibility of life on present-day Mars has not been conclusively eliminated, it does not appear likely.

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