Have any structures been discovered on Mars?
Did myriads of microbes live on Mars?
US research team is certain: there are traces of life in the Mars meteorite ALH 84001
The never-ending story of the controversially discussed Mars meteoride ALH84001 has been enriched by one chapter. After multiple examinations of the microscopic magnetite crystals embedded in carbonate inclusions, which are said to have been produced by bacteria - at least according to the assertion of some NASA researchers - the oval magnetite crystals enclosed in the Martian rock have now been examined more thoroughly than ever before. After three years of intensive study, the US scientist and project manager Kathie Thomas-Keprta is now presenting the research results in the journal "Applied and Environmental Microbiology". And these have it all: For the nine-strong team of scientists there is no longer any doubt that the legendary Mars meteorite ALH84001 contains crystals generated by bacteria. In other words, Mars was a planet of life in its youth.
Even insiders were amazed at the news at the time. When NASA presented a small, inconspicuous stone to the world public on August 6, 1996 in a surprisingly convened, but nevertheless much noticed press conference in front of running cameras, which, according to the NASA research group led by David S. McKay from the Johnson Space Center, came from the planet Mars and Inside of which worm-like structures were encountered, which originated from bacterial Martian life forms, the sensation seemed perfect. In no time at all, the news spread around the globe that the thousand nine hundred and forty gram heavy and potato-tuber-sized meteorite apparently contained fossil remains of a microbe-like alien life form. The word reached the most remote corners of the world that we humans once had brothers in space in the immediate vicinity, even though they did not get beyond the stage of a microbe back then.
Origin of the cosmic fossil undoubtedly
Hardly any other stone in human history has been examined so thoroughly and critically to this day as the now almost legendary Mars meteorite ALH84001, which was released on December 27, 1984 by a team from the National Science Foundation in Antarctica was picked up and its origin was confirmed by chemical laboratory tests: The isotope ratios of the oxygen in the meteorite and the noble gases trapped there as well as the isotope characteristics of the nitrogen inclusions corresponded to the "Viking" results of 1976. ALH84001 was an envoy from the Red Planet. The age of the small rock also indicated a Martian descent.
The investigations showed that the gray-brown, angular chunk was a proud 4.5 billion years under its belt, i.e. it must have been formed immediately after the formation of the red planet. Everything indicated that the rock fell on Mother Earth after an impact event on Mars. A planetoid or comet probably collided with the red planet around 16 million years ago, hurling large amounts of Martian rock into interplanetary space. After another collision in space, the meteorite was thrown to earth 13,000 years ago.
Even more impressive than the results of the chemical analyzes, however, were the images of the supposed microbes themselves, the outlines of which could be clearly seen thanks to electron microscopic magnification. Today everyone, whether supporter or critic of the exo-microbe theory, who dares to take a look into the microcosm, can convince himself via the Internet that numerous bizarre imprints of tiny, thread-like structures can be seen in the fossil stone, which strongly resemble a Colony of fossilized terrestrial rod-shaped bacteria remind, whereby literally "literally" catches the eye that the microscopic nanostructures (ie size in the nanometer range) were a hundred times smaller than their terrestrial "colleagues".
Of course, it didn't take long for the first critics to speak out. Their criticism focused primarily on the question of whether the supposedly thread-like structures that were also discovered in another Martian meteorite were de facto due to some form of life or were nothing more than crystal-like structures. In particular, the theory of the "magnetofossils", with which NASA scientists came to the public in 1996, came under the crossfire of criticism. To this day, the discussion, in which all conceivable arguments for and against have been cited, continues incessantly. After a renewed examination of the rock last November, a team of researchers led by Peter Buseck from Arizona State University came to the conclusion that there was "insufficient evidence" of an organic origin of the magnetic crystals.
Kathe L. Thomas-Keprta believes in life on Mars
Six years after the legendary press conference, the US space agency is now coming up with a new message that is sure to fuel the discourse again. A team of US scientists has found new evidence that there are traces of strange life in the legendary Martian meteorite. As the team leader and NASA astrobiologist Kathie L. Thomas-Keprta recently explained in an article in the journal Applied and Environmental Microbiology, long-term laboratory studies have shown that 25 percent of the "magnetotactic" material in ALH84001 was generated by bacteria on Mars.
In order to be able to provide evidence of traces of life trapped in the Martian rock and to break down the extent to which the presence of the crystals is inorganically caused or due to bacteria, the scientists examined six biosignatures. In contrast to previous analyzes, in which only individual properties of the crystals were taken into account, this time the researchers studied all six physical and chemical properties of the crystals for the first time. Since so-called magnetotactic bacteria are also formed in various inorganic processes on earth and are accordingly common, the researchers focused exclusively on the mineral magnetite.
Bacteria that produce magnetite feel right at home on our planet, especially in watery environments. The terrestrial microbes differ from inorganically produced crystals in that they have no crystal defects, ie they are chemically "pure". Such bacteria have a characteristic size and shape, and a certain group of them (MV-1) has a crystal lattice that forms a chain of around twelve well-ordered magnetite crystals in the cells. When the bacteria go looking for food, they use these chains of magnetite crystals inside their cells like a compass. All of these bacteria make only one specific type of crystal that is around 30 to 120 nanometers (billionths of a meter) in size.
If the researchers found in previous investigations that about a quarter of the tiny magnetite crystals in ALH84001 have remarkable physical and chemical similarities with the magnetite particles formed by terrestrial bacteria, Kathie Thomas-Keprta and her team were able to fully confirm this suspicion, and even more so as this: "No non-biological magnetite population that arose naturally or in the laboratory has ever met our criteria for a biological signature," explains Kathie L. Thomas-Keprta. "This means that a quarter of the magnetite crystals contained in the carbonates of the Martian meteorite ALH84001 need a biological influence to explain their presence." According to the new study, the magnetites in ALH84001 can best be explained as a mixture of biological and inorganic processes that were active on early Mars, emphasizes the NASA astrobiologist.
Magnetic compass needles
In all of this, the magnetite crystal thesis benefits from the fact that the evidence that speaks for the origin and development of life on "archaic" Mars is gradually increasing. The dried up rivers that have been found on Mars so far and the traces of currents there on craters or coastlines, which must have come from a former ocean, provide impressive evidence that abundant water must have flowed on Mars in the past. That is why many experts assume that frozen water can be found at the Martian Poles and the gaseous variant of it can be found in certain thin clouds.
So it is not surprising that the majority of Mars researchers on the Red Planet suspect primitive forms of life or at least traces of former life in deeper layers or in other regions. For NASA scientist Dr. Irme Friedmann has no doubt that microbes once lived on Mars, at least in the distant past. "At the same time that life appeared on Earth, it also appeared on Mars". Dr. Gerda Horneck, who has been head of the Radiation Biology department at the DLR Institute of Aerospace Medicine in Cologne for many years, is optimistic: "There are plausible reasons that traces of life could exist on Mars. Should if we actually find some, it would be clear: life belongs to the cosmic standard. "
As early as March of this year, the 2001 Mars Odyssey space probe was able to record its first success after the start of its official work phase, when it examined the surface of the red planet for the first time on an official mission with the help of the gamma-ray spectrometer and was in the vicinity of the South Pole immediately discovered considerable amounts of hydrogen which, according to the scientists, are embedded in a layer of ice, i.e. frozen water. "The first data from the gamma-ray spectrometer indicate that there is very likely hydrogen just below the surface of Mars," said Dr. Jim Gravin, the lead scientist for the MARS Exploration Program at NASA Headquarters in Washington, D.C.
Last but not least, the data published in June from the space probe missions Mars Global Surveyor and Mars Odyssey seem to confirm the theory of the magnetic "compass needles". According to this, when ALH84001 celebrated its birth 4.5 billion years ago, Mars had a strong magnetic field. At this point in time, the prerequisites and conditions were ideal for the archaic bacteria to be able to produce magnetic materials. "Our best working hypothesis is that the early days of Mars enabled the development of bacteria that shared several properties with the magnetite-forming bacteria on earth, particularly with the MV-1 group," explains Simon Clemett of NASA's Johnson Space Center who co-authored the publication.
Incidentally, the international team of nine, headed by Thomas-Keprtra, worked on the study for a total of three years. The project was financed by the NASA Astrobiological Institute.
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