mars3

In the 1950s the Soviet writer F. Zigel pointed out how strange it was
that astronomers observing Mars during the favorable opposition of
1862 did not report seeing any satellites, but that Asaph Hall, fifteen
years later with a smaller telescope, discovered both Phobos and
Deimos. Zigel said that if the moons existed in 1862, they must have
been visible. The fact that they were not reported indicated they
weren't there at the time. He concluded, then, that Phobos and
Deimos had been launched into orbit between 1862 and 1877.
Shortly afterward, Iosef Shklovskii, in his book Intelligent Life in the
Universe, showed that Zigel's conjecture is flawed. But he also noted
that Phobos is sinking slowly toward Mars. He reasoned that because
of its size (twelve miles in diameter), Phobos could not diminish its
orbit as a result of Mars' atmosphere unless the atmosphere was very
high. Since most planetary scientists of the time were sure the
atmosphere was not very high, Shklovskii explained the shrinking
orbit by suggesting Phobos was very light, so light, in fact, that it must
be hollow. If it was hollow, then it could not be a naturally occurring
planetary body, and must be artificial. If it was artificial, then it must
have been placed there by Martian inhabitants. Or somebody. In the
1960s Carl Sagan added chapters to Shklovskii's book, and the hope
that there might be life on Mars persisted.
Then in July of 1965, Mariner 4 rushed past the red planet and in half
an hour took 22 photographs which apparently settled the Martian
intelligent-life problem for good. The low-resolution pictures revealed
a barren, rocky, sandy, bleak surface, like the Moon's. The dark
patches interpreted by Lowell and others as water and vegetation
became, in the perception of planetary scientists, simply rocks covered
by blown sand of varying colors. After all, Mars was dead.
In 1971-72 Mariner 9 photographed and mapped the entire planet,
revealing not only deserts and sand, but gigantic mountains and
chasms and, more importantly, channeling features which looked like
dry riverbeds. After much skeptical debate and the analysis of piles of
data returned by Viking, Pathfinder and Mars Global Surveyor, it is
now generally believed that water once flowed on Mars. It must have
flowed long ago in geologic time - probably 3.5 billion years ago - but
flowed nonetheless. The Mariner 9 photos indicated that substantial
amounts of water exist in the polar regions as ice and in the
atmosphere as water vapor, and may exist as liquid a few hundred
yards underground where the temperature is warmer. Mars' north pole
has a permanent water ice cap that becomes encrusted with carbon
dioxide ice freezing out of the atmosphere during the northern winter.
By 1976, geologists reviewing Viking's orbiter photographs suggested
that some surface erosion was due to glaciers. All this means that
there is or was lots of water on Mars. Where there is lots of water, life
can exist.
After the Viking landers touched down on the Martian surface in July
and September of 1976, the hope for Martian life dwindled further in
the scientific community. The Viking landers performed three biology
experiments, which have been interpreted variously as either
ambiguous or absolutely negative. The landers scooped up soil and
brought it inside. The soil was treated in different ways with
radioactive carbon compounds and chemical nutrients, and then
monitored for signs that microscopic organisms had metabolized the
nutrients. Originally it was reasoned that if metabolic activity was
taking place, then traces of organic molecules and carbon dioxide gas
would be detectable. And in fact, there were some unusual results,
raising hopes. But no large organic molecules, like those necessary to
life, were found at either site. And in any case it could all be explained
by the chemistry of the soil, which seems to be affected by ultraviolet
radiation in ways that would give rise to the Viking results and also
preclude the possibility of life as we know it.

Mars is, scientifically speaking, lifeless. It is neither what Kepler
hoped for nor what Herschel conjectured was possible. The
speculations of Lowell and Flammarion, and Zigel and Shklovskii,
were hasty hypotheses at best, and hopeful fantasies at worst.

* * *

The possibility still exists, however, even if remotely in the scientific
view, that Mars used to be inhabited when its atmosphere was thick
enough to support liquid water. It's possible that there are Martian
fossils, for example. In the 1960s Carl Sagan pointed out that the rust
in Mars' surface was caused by oxidation, and that oxidation directly
indicates there was considerable oxygen in the Martian atmosphere at
some time in the geologic past. Since the oxygen in the Earth's
atmosphere is believed to come directly from photosynthesizing plants,
Sagan reasoned that life-forms could have - or even must have -
generated the oxygen that oxidized the soil of Mars. Therefore life
might have existed on Mars at one time. And in 1996 a team of
researchers announced that ancient meteorites - pieces of Mars that
had blown through space to Earth - had been recovered in Antarctica
and contained what looked like the fossils of microorganisms. This
implied, they said, that the microorganisms had originated on Mars.
The scientific community was hopeful, but skeptical.
The boundaries of possible extraterrestrial life in the solar system have
narrowed to either Mars' remote past, or to Jupiter's moon Europa,
which may have a liquid water ocean under its solid ice crust, or to
Saturn's moon Titan, which has a thick atmosphere that might support
living organisms. Beyond these ideas, the possibilities for other life
reside in other parts of the galaxy. Reputable scientists like Sagan have
spent much energy raising money to fund the Search for
Extraterrestrial Intelligence, or SETI as it's commonly known. A
complex of huge radio telescopes scans the sky for radio signals with
patterns. One group of scientists in Berkeley has pulled together a
worldwide network of over two million private PCs to process data
gathered by the Arecibo telescope in Puerto Rico. These are some very
hopeful scientists.
What the scientists assume they might find is in some ways very
clearly defined. Although extraterrestrials might look nothing like us,
they will act like us. That is, they will develop the same technologies
and communications systems as we do. Hence the millions that go into
SETI, to listen for radio signals. Any extraterrestrials we encounter will
be advanced, like us.
The evidence for extraterrestrial life will not consist, for example, of
architecture. Finding architectural evidence of alien life would lie
outside the boundaries of our sense of technological advancement, and
hence would not be worth even looking at. This boundary was made
plain by both NASA and spokespeople like Carl Sagan who in the
1980s and '90s went out of their ways to discredit hypotheses about
the strange-looking photographs made by Viking I in 1976 of the land
forms in Mars' Cydonia region, at about 41 north latitude, 10 west
longitude.