Life's Building Blocks
Organic molecules inside space rock were probably the result of plain old chemistry Chemicals in a Martian meteorite that were once held up as possible evidence of life on ancient Mars were more likely the product of heat, water and chemistry, according to a new study.
Researchers from the Carnegie Institution of Washington and the University of Oslo in Norway reached that conclusion after comparing the four-pound (two-kilogram) extraterrestrial rock, ALH84001, with samples of earthly volcanic material—and discovering a matching pattern of minerals consistent with a chemical process that yields carbon compounds after rapid heating and cooling.
Although the study does not support the existence of life on Mars, researchers say it shows that some of the chemical precursors of life—at least as we know it—were kicking around on the Red Planet some 4.5 billion years ago.
Discovered in 1984 in AllanHills, Antarctica, researchers believe that meteorite ALH84001 struck Earth some 3.5 to four billion years ago after being kicked up from the Martian surface and into space by the impact of another meteorite. NASA researchers triggered international headlines in 1996 when they discovered, among other possible indicators of life, traces of polycyclic aromatic hydrocarbons (multiringed carbon molecules found in living cells) along surface fractures in ALH84001.
Initial excitement that such compounds might represent traces of Martian microbes faded within a year or two as researchers came up with other possible explanations for the meteorite's unique features.
"What was missing was whether Mars could actually undertake organic chemistry itself," says Carnegie geophysicist Andrew Steele, who led the new study. To find out, he and his colleagues examined the chemical makeup of 0.1-millimeter carbon globules from samples taken at several depths from ALH84001.
They identified rings of magnetite (iron oxide) arranged around the sooty spheres in the same pattern as in frocks from a volcano on the island of Svalbard, Norway.
"This process may be making a lot of the stuff of life, without any help from things that are alive," says John Rummel, senior scientist for astrobiology for NASA's Planetary Science Division, who was not involved in the study. And that, he adds, means there could still be life there waiting to be discovered.
Kemo D. (a.k.a. no.7)