The question hangs in the air and brings forth nothing more than a few chuckles at Savannah River Ecology Laboratory. In fact, whether there is sufficient proof of life on Mars is something Christopher Romanek's team is still working on. The results could have implications not only for the Red Planet but also for the early life of this planet.
Dr. Romanek was one of 10 co-authors on the latest paper, published Tuesday in the Proceedings of the National Academy of Sciences, on the Martian meteorite Allen Hills 84001, or ALH84001. The potato-size chunk of rock first attracted international attention in 1996 when a research team that included Dr. Romanek proposed that tiny structures within the rock could be the fossils of bacteria or similar simple life forms. Although their findings were then widely attacked, the team has been working ever since to build on that evidence.
The latest discovery comes from tiny grains within the fossillike circles, little rectangular grains of a magnetic mineral known as magnetite that is measured in nanometers, billionths of a meter. Leaning over a photograph of the microscopic, orange-tinted bloblike fossil shapes, Dr. Romanek traces the dark outline of one, where the majority of the tiny magnetite grains are found.
"And it is these little magnetite grains that are so very important to this meteorite and so very important to our studies here," Dr. Romanek said.
Lead author Kathie Thomas-Keprta of the Johnson Space Center made an exhaustive catalog of the properties of those tiny grains and compared them to magnetites found on Earth. And the only place where she found a close match was in a magnetite formed by a type of bacteria that uses it for navigation.
In an accompanying paper, another researcher found that the magnetites in the meteorite formed a chain, similar to what they do in the Earth's bacteria, Dr. Romanek said.
"You can go down to the Augusta Canal, and if you take a sample of the water at the sediment-water interface, where you get a little sample of mud and a little water, you will find these bacteria," Dr. Romanek said.
But while other colleagues offer it as proof of life, Dr. Romanek said he is taking a more conservative approach.
"It's a very big jump from a little mineral grain found in a meteorite to life on Mars," Dr. Romanek said. Still, "You can't refute the fact that the only ones we find on Earth that look like the ones in the meteorite are formed by bacteria."
The theory seems to fit with recent findings that show Mars once had a much stronger magnetic field than it does today, and recent photos appear to show ancient floodplains and even ancient oceans.
"If there were organisms from early Mars, maybe they were adapting to, they sensed the magnetic field and evolved the structures that allowed them to figure out where to be in cracks and crevices and water bodies that once clearly existed on the surface, based on all the images we've gotten back from Mars" that show where water once might have flowed, Dr. Romanek speculated.
For now, his laboratory, with grants from the NASA Astrobiology Institute, is attempting to regrow the magnetites in inorganic conditions that might have existed on the crust of Mars at the time.
The results could have implications not only for Mars but also for Earth, where evidence from the Archeon era, about 3 billion years ago, appears to show magnetites and a similar mineral called siderite, said postdoctoral student Conchi Jimenez, who, with her husband, Dr. Alejandro Rodriguez, is part of Dr. Romanek's team.
"Nobody knows if they are from bacteria or from the physical, chemical environment," Dr. Jimenez said. "They could have been produced just by the chemical environment."
Because she is carefully monitoring and controlling the environment under which the minerals are formed, if they can be formed just by the chemical environment, "We can guess what was the composition of the Earth's atmosphere and its evolution over all these years," Dr. Jimenez said.
While the research has already had an impact on what future Mars missions might do, researchers in the Aiken lab are looking to build more evidence before they make a case for life on Mars.
" It's really quite unresolved," Dr. Romanek said. "But we see hints that may tell us something a little bit more, and that's what is really exciting for us about this research."
Reach Tom Corwin at (706) 823-3213.
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