In the latest study of a 4.5 billion-year-old Martian meteorite, researchers have presented new evidence confirming that 25 percent of the magnetic material in the meteorite was produced by ancient bacteria on Mars. These latest results were published in the journal Applied and Environmental Microbiology. The researchers used six physical properties they refer to as the Magnetite Assay for Biogenicity (MAB) to compare all the magnetic material found in the ancient meteorite — using the MAB as a biosignature. A biosignature is a physical and/or chemical marker of life that does not occur through random processes or human intervention.