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Life on Mars
Geology professor spends summer looking for life on Mars.
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The story begins 4.5 billion years ago when rock was formed on Mars.
Fast-forward to 15 million years ago to a point in time when a huge comet
or asteroid impacted the Martian surface and cast meteorites into the
solar system.
The meteorites traveled through space for millions of years until they
were captured by another planet’s gravitational pull. That happened
13,000 years ago, when a meteorite found its way into the Earth’s
orbit before landing on what is now Antarctica.
In 1984 that meteorite (know as ALH84001) was found in the Allan Hills
ice field in Antarctica during an expedition by a team from NASA’s
Johnson Space Center (JSC).
It is one of only 14 meteorites from Mars that have been found on Earth.
NASA scientists at JSC studying ALH84001 found four independent lines
of evidence of ancient life on Mars, including the abundant polycyclic
aromatic hydrocarbons (PAHs) detected from the fresh fracture surfaces
of the Martian meteorite ALH84001.
In a paper published in 1996, the lead author, David McKay, argues that
the PAHs and their associated secondary mineral phases and textures could
be fossil remains of a past Martian life form.
Work is still being conducted on ALH84001 by NASA and Jiasong Fang, assistant
professor of geological and atmospheric sciences. Fang spent last summer
working with McKay and others at NASA as part of the NASA Faculty Fellowship
Program (NFFP).
The NFFP offers science and engineering faculty at U.S. colleges and universities
hands-on exposure to NASA's research challenges during 10-week summer
research residencies and extended research opportunities at participating
NASA research centers.
"Searching for evidence of life elsewhere in the universe and specifically
within our solar system is one of the most prominent scientific inquires
in human history," Fang says, "and determining if life exists
elsewhere in the universe is one of the key missions of the Space Science
Enterprise areas of NASA."
Fang says an important issue to consider in the search for extinct or
extant life on Mars or other planets is the choice of biomarkers. Biomakers
must play a major role in the biochemistry of any known organism on Earth
if life on Mars and other planets is also carbon-based aqueous chemistry
and the biochemistry is the same.
"A basic characteristic of life is the cell membrane, which separates
the molecularly highly organized organisms from its far less ordered environment,"
Fang said. "Phospholipds are major components of cell membranes of
all organisms and form lipid bilayers in biomembranes. So we can use phospholipids
as biomarkers of choice."
During his summer residency at NASA, Fang worked on several different
areas in regards to ALH84001.
"First we wanted to develop an analytical technique that is sensitive
and contamination-free, to extract lipids from the meteorite," he
said. "Because there is no direct evidence that a living entity evolved
or exists on Mars and membrane is a basic characteristic of all life as
we know it, analysis for lipids from Martian meteorites would provide
an unambiguous way of detecting extinct or extant life on Mars. "
Fang and his NASA counterparts analyzed two lunar (JSC-1) and Mars (JSC
MARS-1) regolith simulants for phospholipids ester-linked fatty acids
(PLFA) through gas chromatography/mass spectrometry. The Mars and lunar
simulants were specifically developed by JSC to support scientific research,
engineering studies and education.
"Our findings suggest that bacteria were dominant microorganisms
in the simulants," Fang said.
Fang hopes to continue his research at NASA and with McKay again this
coming summer when work is scheduled to develop probes that could be used
to detect DNA, protein and lipids. Those probes could then be sent to
Mars on robotic missions.
Around LAS
December 2-31, 2002
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