Since the 1984 discovery in Antarctica of meteorite AHL 84001, the scientific arguments for and against proof of life on Mars have proliferated at an incredible rate. The meteorite, (insert link to Secret Life of Mars) containing what scientists say are the shapes of elementary bacteria, is held to be proof that some kind of basic life form existed on Mars, as much as 3.6 billion years ago.
Their theory received a substantial boost in December of 2000, with the report in Geochimica et Cosmochimica Acta, that AHL 84001 had also proved to hold magnetite crystals, which were identical to the crystals used by aqueous bacteria on Earth, as compasses to locate food sources.
On Earth, these crystals are produced by inorganic means, and have a clearly defined structure. Those produced by magnetotatic bacteria, are chemically pure, contain no defects, and have distinct shapes. The bacteria arrange the crystals in a pattern inside their own cells. To date, nobody has found or been able to create, terrestrial magnetite crystals that are identical to biologically produced ones.
The report was coauthored by a number of scientists including NASA’s David McKay, the first to raise the issue of bacterial evidence within 84001. One of the authors, Joseph Kirschvink of the California Institute of Technology, notes that biological evolution has caused the bacteria to make perfect bar magnets, a goal that has defeated the makers of magnetic tapes and disk drives, for the last 50 years.
Some of the original issues facing McKay in his 1996 study showing the shapes of what he identified as primitive bacteria, were whether or not the bacteria could have been introduced on Earth while the meteorite lay for 13,000 years in the Antarctic ice desert, or even if it had been contaminated from within their laboratory. Thanks to the work of coauthor Chris Romanek, who was able to prove that the carbonites in 84001 were formed on Mars, the team was now able to say that the magnetite crystals were also Martian in origin, since they were embedded in the carbonites.
Electron microscopy was used to examine the nearly invisible crystals, a billion of which could fit on a pinhead. Mars being smaller than Earth, may have developed faster, advancing the evolution of the tiny magnets. However, there was no evidence of strong magnetic fields on the planet, until the Mars Global Surveyor detected in the late 1990s, magnetized stripes in the planet crust, their date coinciding with the timeline for when the carbonates themselves developed.
The discovery only leads to further questions. No life form exists without water. Did Mars have a water source? What happened to that source? When did it disappear? Were these primitive bacteria the only life form, to ever inhabit Mars?