Ancient Plant Matter Found in Waste Dump's Salt Walls

Matt Mygatt in Albuquerque, New Mexico
Associated Press

April 15, 2008

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.

Cellulose is an organic compound that is the main structural component in the cell walls of green plants and algae.

The compound was discovered in water locked in tiny cubes of clear and reddish-brown salt crystals at the federal government's Waste Isolation Pilot Plant (WIPP) near Carlsbad.

The crystals were taken from newly mined areas 2,000 feet (610 meters) 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," he said.

"The others were found in crystal that is smaller and finer and in jumbles with sulfur or clay deposits."

Griffith said looking for cellulose in salt deposits could offer insight into the search for life on other planets, because the hardy compound would be a good target for signs of ancient organisms.

(Related: "Hundreds of Salt Deposits Spotted on Mars" [March 20, 2008].)

He and colleagues present their findings in the April issue of the journal Astrobiology.

Not Fossilized

Griffith's team used a tiny drill about the width of a cat's whisker to bore into the water-bearing cubes and retrieve drops of water.

"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 sea that existed during the Permian period, which lasted from 299 to 251 million years ago, created the 2,000-foot-thick bed of salt that contains the waste disposal facility.

The water drops were placed in a centrifuge and the sediments from the water 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, which is probably remnants of filamentous algae, is significant and exciting, said Karl Niklas, a professor at Cornell University's department of plant biology who was not involved in the work.

"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.

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," lead author Griffith said.

"Bacterial colonies could use it to synthesize mats. They could coat themselves with it for protection," he said.

"Not only is [cellulose] extremely stable, but it's also by far the single most abundant molecule on the planet," Griffith added.

Plants, algae, and bacteria generate about a hundred 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, Michigan—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.