Cellulose dating back 253 million years — along with some possible ancient DNA — has been found in salt crystals from an underground nuclear waste dump in southern New Mexico.
"We did see some ancient DNA in the salt, but not a lot, and we have to continue experiments to try to verify that it is ancient DNA," said Jack D. Griffith, a professor of microbiology and immunology at the University of North Carolina School of Medicine.
The cellulose — the same microscopic stuff in wood or cotton — was in water locked in tiny cubes of clear and reddish-brown salt crystals at the federal government's Waste Isolation Pilot Plant near Carlsbad.
The crystals were taken from newly mined areas 2,000 feet below WIPP's desert surface last fall and a couple of years ago, Griffith said last week.
"We found one in a wall that was a couple of feet across, almost looking like into a huge frozen block of ice. The others were found in crystal that is smaller and finer and in jumbles with sulfur or clay deposits," he said.
The research by Griffith and four co-authors was published in the April issue of the journal Astrobiology.
Griffith said he thinks looking for cellulose in salt deposits is a good way to go searching for life on other planets because cellulose is tough.
He and his colleagues used a tiny drill — about the width of a cat's whisker — to bore into the water-bearing cubes to retrieve drops of water as large as one from a standard eyedropper.
"These inclusions contain saturated salt water that is basically a time capsule that is a quarter-of-a-billion years old," Griffith said.
Evaporation cycles from a Permian sea created a 2,000-foot-thick bed of salt.
The water drops were placed in a centrifuge and the remaining pellets were examined with an electron microscope.
"We were thinking we might see bacteria or bacteria viruses or DNA," Griffith said.
"But there were all these mats of this fibrous stuff," which further tests and research found to be cellulose, he said.
The cellulose looks like a web of tangled angel hair pasta. The fibers are about twice the diameter of a DNA molecule.
The discovery of the cellulose, probably remnants of filamentous algae, is significant and exciting, said Karl Niklas, a professor at Cornell University's Department of Plant Biology.
"The cell walls were preserved, so they (Griffith's team) have native cellulose," Niklas said.
The ancient cellulose was not fossilized — a process in which biological material is replaced by minerals, making a rock.
Cellulose is "a fairly simple structure. And it's probably a fairly simple step for the earliest life forms a couple of billion years ago to start stringing these things together one after another," Griffith said.
"Bacterial colonies could use it to synthesize mats. They could coat themselves with it for protection," he said.
"Not only is it (cellulose) extremely stable, but it's also by far the single most abundant molecule on the planet," Griffith said.
Plants, algae and bacteria generate about 100 gigatons of cellulose a year, he said.
"We're kind of living in a soup of this stuff," Griffith said.
Griffith and his students have talked about going into older salt beds — such as an almost 400 million-year-old deposit under Detroit — to look for cellulose.
"The joke has been that this is the first time students want to be sent to the salt mines," he said.