Science News

 Mud worth more than gold

 

Whillans Ice Stream, Antarctica — Reed Scherer and Ross Powell have studied mud from all over the world. It is different in each place. Mud from the Sulu Sea near Borneo is as smooth as cream cheese. Mud from Chesapeake Bay, in the mid-Atlantic United States, clings to your skin like peanut butter. Okefenokee Swamp mud, from Georgia, stinks with the rotting goo of plants and animals that died long ago. You can tell a lot about a place by reading its mud. But sometimes that mud is hard to come by.
At 8 a.m. on Jan. 30, 2013, Scherer and Powell stood nervously outside in a cold wind. The two men had picked a strange place to look for mud. In every direction, pristine white ice stretched out as far as the eye could see. This remote spot in Antarctica was just 600 kilometers (375 miles) from the South Pole.
Antarctica’s ice covers an area nearly twice as large as the lower 48 U.S. states. Its depth where Scherer and Powell were standing was equal to nine Statues of Liberty stacked on top of each other. There was not a speck of brown on the surface of the ice. But deep below lay the real Antarctica — a hidden continent of rock, water and mud. Far below their boots was Lake Whillans, a body of water no human has ever seen.
Scherer and Powell had traveled to the bottom of the world from Northern Illinois University in DeKalb. Scherer is a micropaleontologist, which means he studies the tiny fossils of things that lived long ago. Powell is a geologist who studies the thick layers of mud and gravel that glaciers leave behind as they move. After years of waiting, they finally hoped to extract samples of mud from the floor of this lake buried beneath the ice.
This muck could help answer important questions. It might reveal how stable Antarctica’s ice has been over hundreds of thousands of years. It might even help scientists predict how quickly the region’s ice will shrink as Earth warms. But scientists also hoped to find evidence of life. Any organisms in the lake’s mud and water might offer clues to what types of life, if any, could exist on distant planets or moons also blanketed in ice.
This was one of the most remote, inhospitable sites that the two scientists had ever visited in search of mud. And there were no guarantees of success. But before the day was over, Scherer and Powell would touch an ancient, distant world — and bear the broad grins to prove it.
Oh, the anticipation
Over the previous week, engineers had slowly, carefully drilled through the ice. Lots of ice. They had to create a hole 800 meters (half a mile) deep to reach Lake Whillans.  Scherer and Powell knew that the lake had a muddy bottom because when the drill first came back up, they found tantalizing traces of mud smeared on it. Now, the two men hoped to grab enough of that mud to do some proper scientific studies. They lowered a contraption with three plastic pipes down a metal cable. They hoped to jam those pipes into the lake bottom and pull up plugs of mud.
But all was not going according to plan. Twice the plastic pipes had gone down. Twice they surfaced empty. No one knew why.
Undaunted, Scherer and Powell had sent the pipes for the third time on an hour-long descent down the narrow hole to the lake.
Now the pipes were coming up again. In anticipation, Scherer and Powell leaned over a metal rail, staring down the hole. The cable crackled and popped as it inched up and out of the hole. Flecks of ice splintered off the line as it coiled back onto a motorized spool.
“Ten meters… seven meters… five meters,” called out the spool operator. He was counting off the last bit of cable before the cores of mud were supposed to rise into view. “Do we have a visual yet?”
“No,” said Powell. He was anxious. Ice drilling is inexact. Lots of expensive scientific gear has been lost in holes, wedged forever in the ice.

Living creature
To probe all of this further, Scherer has wanted to get more mud. Those samples could tell him the last time the West Antarctic Ice Sheet collapsed, meaning that it had suddenly vanished.
“That’s something I’ve been trying to address through my whole career,” he notes. “Scientists had known it had collapsed, but not precisely when that was.”
So Scherer was thrilled at the chance to grab another precious sample of mud earlier this year.
The drill punched into Lake Whillans on January 27. At 11 p.m., 30 scientists and drillers gathered in a wooden hut to make final plans. Slawek Tulaczyk stood and spoke first. The group’s ice expert, he comes from the University of California, Santa Cruz. He noted that the hole, no wider than a large pizza, would gradually freeze shut from the intense cold.
Another problem might also occur, he notes. Most people see ice as solid and hard, like glass. But when the ice is more than a few hundred meters thick, as it was here, it behaves in strange ways. The immense weight pressing down from above causes the ice to squish and ooze like Silly Putty. As a result, the walls of the hole might actually squeeze shut.
“This borehole is a living creature,” Tulaczyk told the group. “It’s changing over time.”  And so began a race against the clock to pull up as many samples of lake water and mud as possible before the hole locked shut.
First, a team of biologists worked nonstop for 20 hours bringing up bottles of water. Fine mineral dust rendered this liquid the color of honey. Within hours, the scientists had samples of the fluid under a microscope. And they found living cells. Each teaspoon of water contained about a half-million of them.
By a narrow margin, those single-celled microbes were the first direct evidence of life in a subglacial lake in Antarctica. (See “Piercing a buried polar lake” to learn more.) A few weeks later, in March, a Russian team would report finding microbes in samples of frozen water from Antarctica’s buried Lake Vostok.
After the biologists at Lake Whillans pulled up their samples of lake water, Scherer and Powell had their turn to probe for mud. On their second try, the equipment bumped into something 760 meters down the hole. It stopped there, only a few agonizing meters short of the lake.
So crews lowered the drill back down the hole to widen it. This ate up 18 hours of precious time. The Antarctic summer was drawing to a close. The team would have to begin leaving within three days — whether Scherer and Powell got their mud or not. So when the mud grabber went down the hole for a third time on the morning of January 30, no one knew how many more tries would be possible.
Frozen goo
At 8:24 a.m., the spool operator counted off the last few meters of cable coming up. “Three and a half meters… one meter.”
People gathered around. Powell and Scherer leaned over the hole. Then something dark came into view.
“We have sediment!” shouted Powell. The onlookers cheered. The thing that emerged from the hole resembled a mudcicle: The dripping glops of brown goo had frozen solid during the journey back up the hole.
As scientists lifted the plastic pipes and carried them into a laboratory, some of the mud splattered around. People rubbed it between their fingers. It was gritty, full of sand that glaciers had mixed in as they bulldozed over the hidden face of Antarctica.
Shattered glass
Scherer’s job looking at diatoms from Lake Whillans will not be easy. He realized this as he looked at those first, limited samples of lake mud from the drill head under a microscope. Sure enough, he saw diatom shells. But they were not the perfect museum art that he had seen in samples from other locations. Instead, imagine that the beautiful diatom shells had been hit by a train and dragged on and on. That is what glaciers do. The dragging had shattered every microscopic diatom shell.
Scherer nudged the slide around, looking for a shell that wasn’t so badly crushed. “I’m a glutton for punishment,” he said, “working on this nasty stuff.”
A person like Scherer who studies diatoms must learn to recognize hundreds of different types. Different species live in different environments. So those in a dab of mud can give clues to the climate in which they had once lived.

 Scratching the Martian surface

It’s dirty work, but something has to do it. Curiosity, the NASA rover that’s been rolling around on Mars for more than a year, recently scooped up some alien soil. Like a lab on wheels, Curiosity used its precise onboard instruments to acquire fine details about the soil. Its first analyses are now in. These data offer scientists the best understanding yet of the Red Planet’s past — and present.
There were a few surprises. Among them: a rock that’s unlike any observed on Mars before. Less surprising, but no less interesting: Researchers report finding the alien soil includes traces of a chemical found in rocket fuel. Rover also found volcanic rocks and glassy substances that contain some water. The findings appear in five research papers, all published in the Sept. 27 issue of Science.
“This is the first time we’ve known precisely and definitively what this stuff is made of,” David Blake told Science News. An astrobiologist, Blake worked on the new studies at the NASA Ames Research Center in Moffett Field, Calif. (Astrobiologists study life everywhere — on Earth and in space.)
Blake and his coworkers analyzed data from an onboard instrument called the alpha-particle X-ray spectrometer. This device bombarded the soil with a beam of radiation known as alpha particles. Some of the radiation bounced back into a nearby detector. The spectrometer measured how energetic the alpha particles were. Scientists used those data to determine that the soil held a blend of volcanic rocks and glassy particles.
Another Curiosity instrument beamed X rays at the soil. X rays are a form of radiation that — like visible light — carry energy as a wave. Different minerals bend or reflect X rays in different ways. So scientists can learn about what’s in the soil by studying how X rays bounce off of and around it.
Scientists can also learn about unknown minerals by melting them and then studying what gases they release. Geochemist Laurie Leshin of the Rensselaer Polytechnic Institute in Troy, N.Y., and her coworkers did just this with the Martian soil. They cooked it at about 835 degrees Celsius (1,535 degrees Fahrenheit) and studied the vapors released.
The soil held some water and a chemical called perchlorate. An ingredient in rocket fuel, perchlorate is poisonous to people. Its presence in the soil could pose risks for any research teams that might one day work on Mars.
The water and perchlorate likely came from the planet’s atmosphere, the new reports say. “The dirt is acting as a bit of a sponge,” Leshin explained to Science News.
Curiosity’s instruments also tested a pyramid-shaped black rock. About the size of a football, the rock had been standing alone. The scientists named the rock “Jake_M” in honor of Jacob “Jake” Matijevic, a NASA engineer who died in 2012.
Jake_M resembles a rare type of rock found on Earth’s volcanic islands.  “It’s not just that it looks sort of like it,” geologist Edward Stolper told Science News. “You would have a hard time telling them apart.”
Stolper, who works at the California Institute of Technology in Pasadena studied the Martian rock.  His team’s analysis of Jake_M may help scientists learn how some rocks formed on Mars. Or, Stolper admits, it may point to a new Martian mystery — especially if it's the only rock of its kind.

First test of Venice's 5.4 billion euro flood barriers

 Flood-prone Venice on Saturday carried out the first test of its 5.4 billion euro ($7.3 billion) barrier system known as "Moses", designed to protect the Renaissance city from rising sea levels.

The ambitious engineering project involves installing 78 mobile barriers divided into four sections at the three inlets to the Venice lagoon, with the largest inlet divided in half by an artificial island.
Fifty companies have been involved in the massive project overseen by the Venezia Nuova consortium, which has been dogged by delays, environmental concerns and scandal.
On Saturday, dozens of officials including Italian Transport Minister Maurizio Lupi were on hand for the first test of the system.
They looked on as four floating barriers were raised at the lagoon's eastern Lido inlet.
"This is a very important and emotional moment," Venice Mayor Giorgio Orsoni told AFP.
"This will change the view one may have about the city and its lagoon, because don't forget, it is a whole, the city and the lagoon are one."
Orsoni added that Venice was "not an amusement park, it is a living city.. and this is a demonstration".
The locks will be activated when the water is 1.10 metres (3.6 feet) above normal levels, said Hermes Redi, Venezia Nuova's director general.
"Therefore, these locks will not defend Venice from all 'acqua alta' (high water) events, they will protect Venice from any exceptional 'acqua alta' events, that is up to a maximum of seven times a year."
Venice is threatened several times a year by the "acqua alta", when the high tide in the Adriatic climbs by about a metre, leading to flooding of the city's most celebrated sites, including St Mark's Square.
The city's vulnerability to rising water levels has worsened dramatically over the years. During the 20th century, Venice sank by 23 centimetres.
The 78 box-shaped barriers will be inserted into immense tanks on the sea floor. When high waters threaten the city, pressurised air will be pumped into the barriers, raising them up on hinges to block the tidal flow.
Once the danger has passed, the air will be expelled and the barriers will fill with water and sink back to the sea floor.
Construction began in 2003, and the system that was initially scheduled to go into operation in 2014 is not expected to be up and running until 2017.
The project has also raised concerns over graft. Under a major investigation into alleged corruption in contracts to build Moses, 14 people were placed under house arrest in July.
Among those detained was Giovanni Mazzacurati, who had stepped down as Nuova Venezia's head in June, along with several members of the consortium and contractors.
Mazzacurati is suspected of "distorting" public tenders for the construction and favouring particular companies.