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- by Francois Durand (www.sasap.freeservers.com) |
Most people become
interested in palaeontology and evolution by asking, 'Where do we come
from?' Every culture, as far as I know, has a unique answer to this
question. For some people it is sufficient to accept Bishop Ussher's
calculation (based on genealogical evidence from the Bible) that people
were created on Friday 28 October 4004 BC, others believe, like Erich von
Däniken, that we are the product, if not the descendants of
extra-terrestrial beings.
Our growing knowledge of astronomy has led to
the realization that our sun is also a star and that statistically there
must be billions upon billions of stars similar to our sun with Earth-like
planets revolving around them, in the universe. The logical conclusion
that follows are that life could have evolved on these planets too. This
conclusion, al-though logical, has put some people in a tight spot - take
Giordano Bruno, for example. This Italian monk stated, already in the
sixteenth century, that 'Innumerable suns exist; in-numerable earths
revolve around these suns in a manner similar to the way the seven planets
revolve around our sun. Living beings inhabit these worlds.' He fled from
Italy in 1576 to avoid a trial on doctrinal charges and lived for several
years in France and England. At the insistence of Giovanni Moncenigo, a
Venetian nobleman, Bruno returned to Italy as his private tutor. In 1592
Moncenigo denounced Bruno to the Inquisition, which tried him for heresy.
When Bruno refused to recant, after spending eight years in jail, he was
burned at the stake in the Campo dei Fiori in Rome.
From
palaeontological and geological evidence it is estimated that life, in the
form of primitive bacteria-like organ-ism, originated on Earth
approximately 3,5 billion years ago (Earth itself is approximately 4,8
billion years old). Bacteria and blue-green algae are known as the Monera
or Prokaryotes and do not possess nuclei or double-membrane organelles, as
do more complex organisms. As far as we know, Monera was the only form of
life for almost three-quarters of the history of life on Earth. It is not
clear yet how life originated from non-living organic com-pounds. One of
the most popular theories was advanced by the American chemist Stanley
Miller who, in 1953, created the building blocks of life from a mixture of
gases, similar to those that made up the atmosphere of ancient Earth. He
managed to produce an organic soup by sending electrical sparks over-night
through a mixture of methane, hydrogen and ammonia.
The fact that the
organic soup contained certain life supporting compounds such as amino
acids, nucleotides, nucleo-sides and carbohydrates thar normally occur in
cells, was very exciting. He postulated that these compounds could have
been formed in the ancient Earth atmosphere by lightning and that it
poured down and accumulated in pools. Complex self-replicating molecules
could have formed in the organic soup filling these pools. Other
scientists argue that these complex molecules could only have formed in
boiling water such as that found in thermal springs. An interesting fact,
which supports this theory, is that some of the most primitive bacteria on
Earth the Thermophiles thrive in the boiling water of hot
springs.
Scientists recently suggested that the ancient Earth
atmosphere could have been made up of carbon dioxide and nitrogen instead
of methane, hydrogen and ammonia. According to them the concentration of
organic compounds, from which life arose on Earth, could have originated
in outer space. Asteroids, comets, meteorites and interplanetary dust
often carry certain organic compounds including amino acids. These
extraterrestrial bodies could have enriched the Earth's surface with
organic compounds over many millennia. This hypothesis might sound
far-fetched until one takes the SNC or Mars meteorites in consideration.
Of the 20 000 meteorites discovered on Earth, 13 display a unique
chemical profile which indicates that they have originated from the planet
Mars. These meteorites consist of basaltic lava, which crystallized only
relatively, recently in the history of the solar system. The indications
are that they have originated from a planet or planets, which was or were
still semi-molten approximately 1,3 billion years ago. The only two
planets in our solar system, which retained enough heat at that time, were
Mars and Venus. Gas bubbles contained within the meteorites have since
proved to be identical to the Martian atmosphere.
NASA scientists
caused uproar when they announced in August 1996 that they had discovered
the fossilized remains of ancient organisms in certain of the SNC
meteorites. Meteorite ALH84001 was discovered in the Allan Hills Ice Field
by members of the American National Scientific Foundation's Antarctic
Meteorite Program in 1984 during their annual expedition.
It consists
of a fragment of a bigger meteorite, which was ripped out of the Martian
crust during a massive meteorite impact there more than 16 million years
ago. After travelling through space over millions of years, it was
captured by Earth's gravitational forces, where it eventually crashed
approximately 13 000 years ago. After studying ALH84001 for two years, a
team of NASA scientists revealed the fact that the meteorite contains
organic molecules, minerals associated with life and microscopically
structures, which resemble bacteria. The largest of these conjectured
fossils is 1/100 of a human hair in diameter while others are ten times
smaller.
Skeptical researchers argue that even if these microscopic
remains were those of bacteria, it would be impossible to be sure of its
origin. Jeffrey Kluger has argued that the meteorite sat on the Antarctic
ice cap for 13 000 years, during which time it could have been
contaminated by Earthly microbes and that the meteorite has been handled
by humans afterwards for two years. The organic compounds in the meteorite
could equally have come from Mars, outer space or from Earth. He also
mentioned another curious possibility - namely, that 'if we allow
planetary cross-pollination from Mars to Earth, why not from Earth to Mars
and back. In fact, Earth's life forms could have originated on Mars, been
transported here by meteorite, and subsequently died out on Mars'.
The
new Mars program will attempt to find answers to some of these tormenting
questions. Few people realize that the present and subsequent Mars
missions will search for evidence of ancient, possibly extinct life, in
other words, it will carry out palaeontological research. These surveys
will also include the search for life-supporting resources, especially
water. Because life on Earth originated in water, it could possibly be
true of Martian life. Secondly, because the origin of life on Earth is so
closely connected to water, we still depend on it. If water is freely
available on Mars, it will broaden our choice for the placement of
economically viable research stations - anywhere else but the
poles.
Signs of free water can be seen nearly everywhere on the Martian
surface. There is also evidence that Mars was much warmer once upon a time
and that rivers and bubbling fountains were common. Old crater rims are
weathered and others are scarred by gullies, which could only have been
carved by running water. In certain areas the Martian surface is scored by
branching networks of valleys, similar to those made by river tributary
systems on Earth. Free water subsequently disappeared from the Martian
surface however. Water only still occurs as ice crystals in the
atmosphere, and on the surface as ice on the pole caps. In the summer
months the ice caps melt partially and the Martian sky is filled with
clouds. But where did the water, which carved gigantic flood channels -
which may be hundreds of kilometers wide and over a thousand kilometers
long - from the Martian surface, disappear? One theory is that most of
this water could occur as a subterraneous layer of up to 500m
thick.
Subterraneous water can also support life. Todd Stevens and Jim
McKinley of the American Pacific Northwest Laboratory in Richland,
Washington, have discovered bacteria in deep aquifers in basalt formations
near Washington. These bacteria are the only known organisms which can
survive without any energy input from the sun, geothermal warmth form the
Earth's interior or chemical energy stored in organic matter. The
bacteria, which were named 'subsurface lithoautotrophic microbial
sub-systems' or 'SLIME', apparently live only on rock and water. Life on
Mars may resemble this.
Dan McCleese, chief scientist of the Mars
Exploration Program laboratory in Pasadena, California, said that they
planned to send exploration robots every 26 months (i.e., when Mars is at
its optimum position to Earth) to Mars. Certain rockets will be sent up in
pairs, the one with an orbiter and the other with a lander. These robots
will each conduct its own set of experiments but the orbiters will also
act as relay stations transmitting data back to Earth from the landers,
and vice versa. The landers will also link up electronically to do joint
experiments. A single lander can report on the weather at a particular
spot on Mars, but a network of landers can monitor the dynamics of the
planet's climate. Similarly, a single lander's seismometer can measure a
quake, but a network of seismometers can measure the size of the planetary
core.
No sign of life or organic material has been detected on the
Martian surface by the Viking landers in 1976 or by the Sojourner robots
in 1997 - possibly because the Martian surface is sterile. 1999 will see
the deployment of new technology, which will include the use of
microprobes. These 2kg probes will fall from space and will crash into the
Martian surface at a speed in excess of 700km per hour. During the impact
the microprobes will split into a forebody and an aftbody system. The
forebody, which will be lodged into the surface at a depth of 0,3-1,9m,
will contain the primary electronic sensors and instruments. The aftbody,
connected to the forebody by an electrical cable, will remain close to the
surface to collect meteorological data and deploy an antenna for relaying
data back to Earth via the orbiters.
According to Dr John McNamee,
manager of the 1998 Mars Surveyor Lander and Orbiter project at NASA's Jet
Propulsion Laboratory (JPL), Pasadena, California, this will be the most
efficient and effective way of obtaining soil samples and measurements
from below the sterilized Martian surface. The microprobes, together with
other landing units, will continue their search for subterraneous water,
minerals and signs of life. In 2005 an unmanned return mission is planned
during which rock and soil samples will be collected by robots and
returned to Earth to be for analysed for, among other things, signs of
life.
We may finally get answers to some of our questions only within
the next twenty years, when the first manned missions to Mars are
planned.
It is a serious indictment of humankind that we accept new
paradigms forged by science as a matter of fact, without reflecting upon
the talents, initiative, diligence and sacrifices of the handful of
scientists who brought it about. Nor does humankind think about the
suffering it would have been subjected to if not for the activities of
these people. But even worse, the man in the street does not think about
his role in the persecution, humiliation and social rejection, which the
scientist often has to suffer. How many people gleefully took part in the
proceedings when Galileo, Bruno, Columbus, Darwin or Wegener were
persecuted for their views on heliocentrism, extraterrestrial life, a
round Earth, evolution or continental drift, only to resignedly (and with
complete amnesia about their previous prejudices) accept the new paradigm
later, when its inescapable truth eventually dawned upon them? If there is
intelligent life out there, what will its opinion be of us? We who
persecute our intellectuals because they rip us from the cosy cave of
ignorance and expose us to the thunderous, alien and uncontrollable music
of the universe.
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Fig. 1: Giordano Bruno, the monk burned at the stake in 1600 for, among other things, postulating the existence of extrasolar planets (statue in Rome, Campo dei Fiori, the site of his martyrdom) |
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| Fig. 2: Meteorite ALH84001, once part of Mars; it contains evidence which suggests that primitive life may have existed on Mars billions of years ago. (Photo: NASA) |
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Fig. 3: Electron microscope image showing an unusual tube-like structural form that is less than 1/100th the width of a human hair in diameter, found in the Allen Hills of Antarctica. |
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Meteorite ALH84001. (Photo:
NASA) |
For more information on Martian
meteorites go to http://www.jpl.nasa.gov/snc/
http://www.sasap.freeservers.com/
Email F. Durand skarab@icon.co.za