Oldest Rock Known to Man
Allen Hills 84001, otherwise abbreviated as ALH84001, is one of 53 meteorites found to have Martian origins. Most meteorites that are found by the US are categorized and brought to the Smithsonian. However, Martian meteorites are of special interest and are kept by NASA for further study. ALH84001 was of particular interest because it is thought to be one of the oldest formed rocks in our solar system.
Evidence of Extraterrestrial Life
In 1996 David McKay (currently the Chief Scientist of Astrobiology at the Johnson Space Center) and his colleagues published an article about ALH84001. They claimed that it contained carbonate that was formed at low temperatures as well as PAH’s (Polycyclic Aromatic Hydrocarbons—thought to be early building blocks of life); and more importantly, it contained magnetite structures that were possibly created through biological processes. If this was true, then this would be the first evidence of extraterrestrial life ever found.
The 1996 publication and subsequent press coverage brought on a fervor of criticism and unintentional growth of budgets for NASA and other programs. Although NASA was already interested in Mars, they had not sent an orbiter to the red planet since 1976, for which they had lost contact with in 1993. Press coverage of the McKay paper in 1996 renewed the interest in the general public and in politics. People wanted to know more. Since 1996 we have returned to Mars with a number of orbiters, landers, and rovers. NASA is also currently working on a long-range science laboratory to be sent to Mars in the near future.
Meanwhile, there were four primary criticisms of McKay’s findings in 1996. One such criticism suggested that ALH84001 had been contaminated by the Antarctic environment after landing on the Earth’s surface 13,000 years ago. Through further study, it was later proven that the structures were indeed formed while on Mars.
Magneto-tactic Bacteria on Mars
Allen Hills 84001
Another criticism pointed out that Mars doesn’t have a magnetic field. Therefore, the suggested magneto-tactic bacteria (a type of bacteria known to produce magnetite to assist in navigation) could not have developed on Mars. Although this is true today, evidence was found in 1998 that Mars once had magnetic regions stronger than those found on Earth.
In 1997 critics illustrated that carbonate globules (pancakes) could only be formed at high temperatures. Therefore, what could possibly be micro-fossils were actually cooling artifacts. These papers found a lot of press and were thought to discredit the McKay paper. In 1998, however, it was found that the carbonate globules had to form at low temperatures because the PAH’s that were also present could not take high temperatures. This reversed the criticism, but didn’t get the same kind of press. So the general consensus that the original paper of 1996 had been discredited remained and much of the general public lost interest in ALH 84001.
Finally, some critics have provided evidence that illustrate how similar forms of magnetite can be formed by non-biological processes. However, McKay contends that although this argument may weaken his hypothesis; it does not entirely dismiss the possibility that some of the magnetite could have been deposited biologically. He also points out that there are still some differences between what has been formed in a lab and what is found within ALH84001.
Meanwhile, the debate continues in scientific circles with this final and most compelling criticism of all. With continued research and returning material from Mars, we may one day settle this argument. Until then, we will continue to study our closest neighbor for all its hidden secrets; and we will continue the search for extraterrestrial life wherever it can be found.
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