Martian Rocks

This essay has a total of 2103 words and 9 pages.

Martian Rocks

H. G. Wells wrote in his book, "War of the Worlds", about Martian invasion toward earth.
He mentioned, "No one would have believed, in the last years of the nineteenth century
that this world was being watched keenly and closely by intelligences greater than man's
and yet as mortal as his own; that as men busied themselves about their various concerns
they were scrutinized and studied, perhaps almost as narrowly as man with a microscope
might scrutinize the transient creatures that swarm and multiply in a drop of water."

Since then it has now been about 100 years Wells based his well-known story of human's
first contact with extraterrestrial life. Now, in the 20th century scientists are starting
to believe what was once a fictional story by writers now actually could be real, becoming
the stuff of science. In 1994 scientists discovered fragments of meteorites which may in
fact prove that signs of early life existed on Mars. Many of these meteorites are found in
the Antarctica, extremely cold weathers aid in preserving and fossilizing the fallen
meteorites for millions of years. In order for scientists to conclude that the meteorites
are from Mars and contain signs of fossilized life or traces of it they must provide
sufficient evidence to support their theory.

Today, a meteorite from Mars is being closely scrutinized by earthly intelligences. The
famous meteorite to bare significant signs of life is the Allan Hills 84001 (ALH84001),
classified as one of the meteorites thought to come from Mars. Due to the atmospheric data
taken by the Viking Lander spacecraft sent to Mars in the 1970s. The data make it possible
to know that gases trapped inside the rock is identical to the Martian atmosphere. "It is
one of only 12 meteorites identified so far that match the unique Martian chemistry
measured by the Viking spacecraft that landed on Mars in 1976" Scientist believed that the
ALH84001 blasted off from the surface of Mars about 16 million years ago by a comet or
asteroid. The rock orbited in the solar system for a few million years and finally reached
Earth about 13, 000 years ago.

Investigation into the ALH84001 and the possibilities for containing remains of ancient
Martian life was assigned to a team of NASA scientists. Dr. David McKay, Dr. Everett
Gibson and Kathie Thomas-Kerpta of Lockhead Martin co-led the team with assistance from a
Stanford team led by Professor of Chemistry Dr. Richard Zare. They investigated different
features in ALH84001, trying to explain their origin and meaning and if these are evidence
for life having once existed on Mars.

The ALH84001 is a rock formed originally from molten lava, containing small rounded
carbonate mineral globules within the tiny cracks and fractures inside the rock. Within
these carbonate minerals that the possibility of life existed on Mars is found. Water is a
necessity in all forms of like. It acts as a solvent and needed for chemical reactions.
Therefore, the minerals are believed to have precipitated from a liquid, possibly water,
which was percolating through the rock. The key features are "carbonate globules"; contain
mineral grains, which are similar to minerals produced by some bacteria on earth.
Therefore it is possible that the mineral grains in ALH84001 could have been produced by
Martian bacteria and would be further evidence that life once existed on Mars. These
carbonates have hot been found in any other Martian meteorites. The ALH84001 weighs about
four pounds it was actually much bigger, due to the entrance through Earth's atmosphere
the rock burned up to the size it is now.

Researchers claim that 3 to 4 billion years ago water containing carbon dioxide percolated
throughout the Martian rock that eventually became ALH84001. This deposited carbonates
inside the meteorite as well as organic molecules, minerals, and even the fossil remains
of Martian bacteria that once flourished in the water. Within the carbonates, were
findings of minerals that could be associated with life. They found iron oxides and
sulfides, which can be produced by anaerobic bacteria and other microbes. "The team found
unusual compounds--iron sulfides and magnetite--that can be produced buy anaerobic
bacteria and other microscopic organisms on Earth" They also found magnetite, which is a
form of iron associated with some earthly bacteria. The size, structure and purity of the
magnetites which can be produced biologically by bacteria on earth, thus they could have
been formed by Martian bacteria. "Impressed by the grains' resemblance in size, shape, and
crystalline regularity to magnetite produced within some terrestrial bacteria, the
researchers argued that bacteria also produced the meteorite's magnetite-martian bacteria,
that is" Such minerals are usually produced as waste products and the grains in ALH84001
are very similar in shape and structure to those produced by earth bacteria. The
conditions under which these minerals were formed means they were probably formed through
a biological process. Although this evidence is very suggestive of life having once
existed on Mars, it is possible that the mineral grains formed by a non-biological process
as well. "Some meteorites carry these compounds, presumably made by nonbiological
processes" The samples analyzed may have been poor examples and have been interpreted in
the wrong way.

Secondly, the scientists identified organic carbon molecules that they believed originated
on Mars. The organic carbon molecules called polycyclic aromatic hydrocarbons (PAHs) were
found in and on the carbonate globules. They identify these PAHs as decay products of
living organisms that flowed in when the carbonates were deposited. PAHs are very common
in the earth's atmosphere and occur from a variety of processes.

The PAHs could have formed while the meteorite was in Antarctica and have entered it from
the atmosphere. They could have occurred by entering the meteorite before it was found in
Antarctica. If so it would be expected that the PAHs would be more common on the outside
and become less abundant towards the center of the meteorite. Investigation shows the
opposite of this found and PAHs were more abundant towards the center of ALH84001. This
would be expected if it was extraterrestrial due to the meteorite burning up upon entry
into the earth's atmosphere vaporizing PAHs near the surface. "No PAHs were found in the
meteorite's exterior crust, but the concetration of PAHs increased in the meteorite's
interior to levels higher that ever found in Antarctica" Also the concentration of PAHs is
greater that what would have been in the atmosphere at the time impacted. Again this makes
the source more likely to be extraterrestrial.
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