Face on Mars
in the Classroom
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
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
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
- "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
- ''The Great
Stone Face and Other Nonmysteries,'' Martin Gardner, The Skeptical Inquirer,
Fall 1985, page 14.
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.
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'
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.
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:
A fourth instrument
pulverized the soil to look for traces of organic matter.
- 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.
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.
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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