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Primitive life in a rock that fell to Earth:

Rocks on Earth Tell Story of Life on Mars


NASA Mars meteorite image S96-12299
NASA Mars meteorite S96-12299
Primitive life may have existed on Mars three billion years ago, National Aeronautics and Space Administration (NASA) scientists said in August 1996 after they analyzed a rock which was dislodged from the Red Planet and fell on Earth as a meteorite some 13,000 years ago.

Meteorites are chunks of metal or stone that survive the fiery passage from Outer Space through Earth's atmosphere. Many of them are thought to be the debris of broken-up comets or asteroids.

The incredible announcement of evidence of ancient life in a meteorite from Mars generated excitement among not only scientists, but the general public as well. NASA said the discovery would accelerate plans to send geology probes to Mars.

Scientists analyzed the fragment of rock from Mars for two and a half years. They found: Tiny structures in the rock resembled single-celled terrestrial bacteria. If the microscopic forms are the remains of living organisms, they would be the first evidence that life has existed on any other world but our own.

No small potatoes. Geologists think the 4.2-lb. potato-size meteorite was ejected from Mars when the planet was bombarded by asteroids millions of years ago. It drifted in space for 16 million years, then landed in Antarctica about 13,000 years ago.

After the rock was discovered in 1984, geologists established it as one of the few meteorites from Mars to be recovered on Earth. The rock's chemical composition is similar to those analyzed by NASA's two Viking landers on Mars in the late 1970s.

Known as ALH84001 for Antarctica's Allan Hills ice field where it was found, the meteorite is by far the oldest of twelve Martian fragments discovered on Earth. It is the only one known to have existed on Mars 3.6 billion to 4 billion years ago when the Red Planet was much warmer and wetter than it is today.

Geologists believe water penetrated fractures under the Martian surface and formed an underground water system. When exposed to the atmosphere of carbon dioxide, that formed carbonate minerals in the fissures of rock. Within the meteorite's fissures, the scientists found veins of carbonate which could have fossilized microscopic forms of Martian life in a fashion similar to the formation of fossils in limestone on Earth.

One of the most intriguing findings from those carbonate sections of the meteorite were microscopic tubular and egg-shaped structures strikingly similar to microscopic fossils of the tiniest terrestrial bacteria. The biggest of the structures are less than 1/100th the diameter of a human hair. Most are about 10 times smaller.


Some details from the findings:

The research team included expertise in microbiology, mineralogy, analytical techniques, geochemistry and organic chemistry. Here are some further details of the findings:
  • Stanford researchers used a dual laser mass spectrometer -- the most sensitive instrument of its kind in the world -- to look for the common family of organic molecules called PAHs. When microorganisms die, the complex organic molecules that they contain frequently degrade into PAHs which often are associated with ancient sedimentary rocks, coals and petroleum on Earth and can be common air pollutants. Not only did the scientists find PAHs in easily detectable amounts in meteorite ALH84001, but they found the molecules were concentrated in the vicinity of the carbonate globules. That appeared consistent with the proposition that they are a result of the fossilization process. In addition, the unique composition of the meteorite's PAHs is consistent with what the scientists expected from the fossilization of very primitive microorganisms. On Earth, PAHs virtually always occur in thousands of forms, but in the meteorite they are dominated by only about a half-dozen different compounds. The simplicity of this mixture, combined with the lack of lightweight PAHs like napthalene, also differs substantially from that of PAHs previously measured in non-Martian meteorites.

  • The team found unusual compounds -- iron sulfides and magnetite -- that can be produced by anaerobic bacteria and other microscopic organisms on Earth. The compounds were found in locations directly associated with the fossil-like structures and carbonate globules in the meteorite. Extreme conditions -- conditions very unlikely to have been encountered by the meteorite -- would have been required to produce these compounds in close proximity to one another if life were not involved. The carbonate also contained tiny grains of magnetite that are almost identical to magnetic fossil remnants often left by certain bacteria found on Earth. Other minerals commonly associated with biological activity on Earth were found in the carbonate as well.

  • The formation of the carbonate or fossils by living organisms while the meteorite was in the Antarctic was deemed unlikely for several reasons:

    • The carbonate was age dated using a parent-daughter isotope method and found to be 3.6 billion years old, and the organic molecules were first detected well within the ancient carbonate.

    • In addition, the team analyzed representative samples of other meteorites from Antarctica and found no evidence of fossil-like structures, organic molecules or possible biologically produced compounds and minerals similar to those in the ALH84001 meteorite.

    • The composition and location of PAHs organic molecules found in the meteorite also appeared to confirm that the possible evidence of life was extraterrestrial. No PAHs were found in the meteorite's exterior crust, but the concentration of PAHs increased in the meteorite's interior to levels higher than ever found in Antarctica. Higher concentrations of PAHs would have likely been found on the exterior of the meteorite, decreasing toward the interior, if the organic molecules are the result of contamination of the meteorite on Earth.

Los Angeles Mars Meteorite
Los Angeles meteorite from Mars
Does it prove there was life on Mars?

It is difficult to prove life existed 3.6 billion years ago on Earth, let alone on Mars. The research team looked to the existing standard of proof which includes having an accurately dated sample that contains native microfossils, mineralogical features characteristic of life, and evidence of complex organic chemistry. NASA pointed out the findings were inconclusive and nothing suggested existence of higher forms of Martian life or "little green men."

The research team included scientists from Stanford University, the University of California at Los Angeles, and NASA's Johnson Space Center. The team's findings were published in the August 16, 1996, issue of Science.

Previous discovery of Mars life

A team of British researchers reported back in 1989 that they had detected organic material inside a meteorite which they surmised had broken off from Mars and hit Antarctica thousands of years ago.

Researchers at England's Open University wrote about their findings in the British journal Nature. They called their examination of the Antarctic meteorite "the first recognition of organic compounds from Mars."

They did not speculate whether the organic material was produced by living creatures or generated by natural weathering processes and they did not determine the exact organic compounds present in the meteorite. They urged that samples be subjected to more-sophisticated tests to learn their precise composition.

Scientists who supported the view that the rare SNC type of meteorite studied by the British came from Mars said that its gas and mineral composition closely resembled conditions thought to exist on Mars.

More discoveries of Mars meteorites

America. A Mars meteorite was found in the Mojave Desert around 1980.
California rock hunter hiking in the Mojave Desert around 1980 picked up two dark stones, but didn't realize their rarity. He stored the rocks in boxes in his backyard until 2000 when he took a second look. They turned out to be the second confirmed Mars meteorite discovery in the United States, according to NASA.

Among the 20,000 meteorites identified on Earth, about 15 are thought to have come from Mars, according to the Jet Propulsion Laboratory in Pasadena, California. The hiker nicknamed his rocks Miguel and Gabriel.

Now known officially as the Los Angeles meteorite, the hiker's find actually is two stones weighing 16 and 9 ounces each. Analysis by the University of California confirmed that they are dark volcanic basaltic rocks from Mars. They are very similar to a Mars meteorite found in the Antarctic in 1994.

The first U.S. find of a Mars meteorite was the so-called Lafayette stone found in Indiana and identified as a Mars meteorite in 1931. It was discovered in the geological collection at Purdue University.
Oman. Another rare Mars meteorite was discovered in the year 2000, this time in the Middle East.
A meteorite hunter combing the deserts of Oman found the brownish gray stone, which was examined at the University of Tennessee and the Vernadsky Institute in Moscow.

The rock's chemistry was similar to a Mars meteorite found in Antarctica, which NASA said showed signs of microscopic fossilized life.

The Sultanate of Oman is on the eastern corner of the Arabian Peninsula. The nation's diverse geography includes beaches, mountains and barren stretches of desert that attract meteorite hunters.

The 37-ounce martian basalt meteorite found there is known officially as the Dhofar 019. As much as 28 ounces of the Mars meteorite may have been sold somewhere on the international rock and gem market. Considering the meteorites to be geological souvenirs from space, sellers can realize as much as $85,000 per ounce ($3,000 per gram) for Mars rocks at auctions.
Western Sahara and Antarctica. Amateur rock collectors discovered Mars meteorites in Earth's hottest and coldest places.
The number of known stones on earth from the Red Planet climbed to 24 as hunters located five more in the coldest and hottest places on Earth in 2000 and 2001.

Some of the 24 rare martian meteorites have revealed clues to whether Mars once had oceans or life.

Actually six chunks of Mars rock were found, but scientists decided that two were from the same meteorite. The Western Sahara find is known as NWA 1068.

One of the meteorites turned out to be the second-largest Mars meteorite fragment ever recovered, accroding to NASA. It weighed 30 lbs.

In addition to the finds in the Oman desert (described above), a separate expedition discovered rocks in Antarctica where no dirt, grass or tree cover makes for ghreat rock collecting.

An estimated 20,000 meteorites strike the Earth every year, but only a handful are thought to have come from Mars. Those Mars meteorites are chunks snapped off of the Red Planet millions of years ago in a comet or asteroid collision. After traveling across interplanetary space, they made it down through Earth's atmosphere to crash onto the deserts, snow fields and other areas of Earth's surface. Some may have landed as recently as within the last one hundred years.

How do we know whether a meteorite came from Mars? Scientists take them into their laboratories to look at their mineral composition and compare trace gases trapped inside the rocks with those gases found on the surface of Mars by our Viking landers in the 1970s.
Could a meteorite be a chunk of Mars?

First, let's straighten out the meteor vs. meteorite confusion. You probably have seen one of those bright streaks of light some people call a shooting star or a falling star. Meteors can be seen streaking across the sky whenever larger stony chunks called meteoroids make a fiery plunge into Earth's atmosphere. Those meteoroids that are not completely burned up and actually reach Earth's surface are called meteorites.

A meteorite usually is a walnut-sized chunk of metallic or stony rock which came from somewhere else in our Solar System or beyond and crashed to our planet's surface. Among the 10,000 or so meteorites found so far, several found in the frozen tundra of Antarctica, in the hinterlands of rural Indiana, in India, Egypt, France, Antarctica, Nigeria and Brazil have been identified by geologists as having originated on Mars.

The supposedly-Martian meteorites display a chemistry similar to rocks analyzed by the two Viking spacecraft which landed on Mars and ran chemical tests in the late 1970s. They show a chemical makeup different from other Earth rocks, but similar to what the Vikings found on Mars.

How the rocks got here from Mars has puzzled scientists.

Opponents of the meteorite-from-Mars theory argue that a crashing asteroid powerful enough to knock a chunk of Mars into space would have melted the chunk completely and no meteorite would have resulted. On the other hand, advocates of the meteorite theory cite evidence that shows small pieces of the Moon have been broken off and reached Earth as meteorites. The advocates claim the same thing could have happened on the Red Planet.

Scientists estimate a rock kicked up from the windswept plains of Mars would have to accelerate to 11,300 miles per hour to escape the planet's gravity and travel out into space. What could cause a rock to move so fast?

Suppose an asteroid of, say, 500 to 5000-ft. diameter was floating past Mars at 16,000 miles per hour. Suppose it struck the planet a glancing blow at an angle of between 25 and 60 degrees. It would be like a golfer making a long drive. The crashing asteroid would kick up dust and gas travelling at 50,000 miles per hour. That vapor would be powerful enough to lift rocks and send them flying away from Mars at 11,300 mph. Sailing along through interplanetary space, some of the rocks would come close enough to Earth to be attracted down onto the face of our planet by its gravity.

Actually, two astrogeologists at California Institute of Technology used a 106-ft. gun to fire off rounds of one-ounce plastic bullets at 16,000 mph. Their gun tests, which simulated an asteroid collision, showed that a huge space rock crashing into Mars at just the right angle would spray of debris moving fast enough to escape the gravity of the Red Planet. That debris then could have hurtled through the Solar System into the arms of Earth's gravity.

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