Meteorites May Have Fostered Life on Earth

From Wired News:

About 470 million years ago, back when our ancestors were jawless fishes and the land was ruled by insects, Earth was pounded by a series of enormous meteorites. The traces of that hammering still survive today in ancient rocks in southern Sweden and central China, where scientists have found exotic mineral grains found only in meteorites.

By measuring the amount of the grains in the rocks, the scientists calculated the rate of meteorite impacts jumped by a factor of 100 around 470 million years ago. A number of the impacts were big enough to leave 20-mile craters. The energy unleashed was 10 million times greater than the energy in the nuclear bomb dropped on Hiroshima.

At the same time, scientists have also been putting together a chronology of fossils from the same time, known as the Ordovician Period. They're recording when species first emerged in the fossil record, and when they disappeared as they became extinct. And this week in the journal Nature Geoscience, the scientists report that the impacts coincided with a drastic change in the world's biodiversity.

You might expect mass extinctions. The most famous of all impacts, a ten-mile-wide asteroid that hit the Earth at the end of the Cretaceous Period 65 million years ago, has been linked to mass extinctions that wiped out Tyrannosaurus rex, the other dinosaurs without wings, and about half of all other species on Earth.

But 470 million years ago, that's not what happened. Instead, the diversity of life took a sharp climb right after the meteorites started falling.

Scientists say the discovery is quite unusual. Nature Geoscience's press release declares, "These results are surprising as meteorite impacts are often more commonly associated with mass extinctions."

But actually, aside from the Cretaceous impact, no other case for impact-triggered mass extinctions has strong support today. Earth has regularly been pummeled by meteorites -- mostly small, but in some cases huge. Many of them have had little effect on life, and some may have actually fostered it. The new study of the meteor shower 470 million years ago is important because it's part of a trend, not an exception to the rule.

It may be hard to imagine that a huge rock from space could not have caused mass extinctions. But that idea is actually relatively new. In the late 1970s, Walter and Luis Alvarez, a father and son team of scientists, and their colleagues offered evidence that something very big hit the Earth right around the time the dinosaurs died, at the end of the Cretaceous Period. They claimed the impact was the kill mechanism. They were greeted with scoffs, but over the next couple decades other scientists found a wealth of supporting evidence, from shocked bits of quartz to the outline of the crater itself buried in Mexico.

The asteroid appears to have caused massive tidal waves and splashed molten rock far and wide, triggering gigantic forest fires. The soot from the fires blackened the sky, which was also loaded with other nasty compounds from the impact that may have caused a global blackout for months, acid rain, and severe global warming. These days, most scientists who study the impact don't think it's a coincidence that this environmental catastrophe came right around the time that 50 percent of the world's species became extinct. If not the sole killer, the impact was at the very least an accessory to the crime.

As years went by, the Cretaceous impact went from shocking hypothesis to icon. Who can count all the paintings that have been made of the crash -- often from a doomed dinosaur's perspective? The impact hypothesis had a big effect on scientists, too. It became a prime example of evolution's contingency, how its path can turn suddenly due to an abrupt change in the environment.

Some scientists began to argue that other impacts may have triggered other extinctions. They offered evidence of a rise in extinctions every 26 million years. They suggested that a star in our neighborhood periodically disturbed the cloud of comets surrounding our solar system, sending some towards our defenseless planet. Other researchers looked at big pulses of extinctions, such as the one at the end of the Permian Period, 250 million years ago, when over 90 percent of species disappeared. A few claimed to find traces of impacts that coincided with those major die-offs as well.

But these theories have lost a lot of their luster. The cycles of extinctions have blurred since scientists have learned how to make more precise estimates of the ages of rocks. It turns out some of the impacts linked to mass extinctions actually hit millions of years before or after the die-offs.

Meanwhile, geochemists and paleontologists are finding evidence that points to other culprits for the mass extinctions. Global warming appears to be behind many of the biggest. Volcanoes can unleash vast amounts of carbon dioxide, and heat-trapping methane can rise up from the sea floor. There's some evidence that these past episodes of global warming triggered a chain reaction of destruction, from the acidification of the oceans to the destruction of the ozone layer. It looks as if our planet can wreak its own destruction without the help of asteroids (or even people).

At the same time, impacts have proven surprisingly impotent. In one study, John Alroy of the National Center for Ecological Analysis and Synthesis, for example, surveyed all the impacts that occurred in the past 65 million years -- including some that left craters 50 miles wide or more. He then compared them to the well-documented fossil record of mammals in North America. He found no link whatsoever between impacts and changes in the extinction rate.

So how could an asteroid cause so much damage at the end of the Cretaceous, and so little at other times? It's always possible that there are extinction-triggering impacts yet to discover. It's also possible that impacts do cause extinctions, but not a lot. Earlier this year, for example, a team of scientists announced that a meteorite may have exploded over North America 12,900 years ago, killing off mastodons and other big mammals of the New World. But that's small potatoes compared to the major die-offs in Earth's history.

It's also possible that the impact at the end of the Cretaceous was a major fluke. It was unusually big, for one thing, forming the third biggest known crater on Earth. Its effects may have also been amplified because of where it hit the planet. Instead of plunging into the deep ocean, it smashed into a shallow shelf of calcium carbonate and other minerals. It lofted this deadly cocktail into the atmosphere, unleashing hell on life below. Smaller impacts that hit other places may not have been able to similarly break Earth's food network.

But how could meteorites drive up the diversity of life? The researchers aren't sure, but they suggest that the impacts may have disturbed old ecosystems, creating a new space in which new species could evolve. They're not the first scientists to argue that meteorites can be beneficial in the long term. A large impact can rework the ocean floor or a shoreline, or even scoop out a new lake. In these new habitats, new species can evolve.

It's particularly intriguing to compare the number of species in crater lakes to other lakes of the same size. Crater lakes are often much more diverse. It's possible the asteroids or comets that scoop out the craters also fertilize them with minerals and other nutrients, supporting more species.

This fertilization from space may have made life itself possible on Earth. Four billion years ago, comets and asteroids delivered water, organic molecules, and other raw materials necessary for life. Some of the early craters may have even served as natural beakers that synthesized new chemicals essential for life. Not every impact was so benign on the early Earth; judging from the craters still preserved on the moon, the biggest ones may have boiled off the oceans. But some researchers have also speculated that microbes could have been lofted into space, where they could have survived on meteorites, or perhaps on other planets, before reseeding Earth.

This new view of impacts doesn't mean that we shouldn't be worried about the asteroids that may cross our path in years to come. But what's bad for human civilization may not be so bad for life as a whole.

Pork workers suffer neurological symptoms from inhaled misty pig brains

From Wired News:

Minn. Slaughterhouse Workers Fall Ill

By MARTIGA LOHN
Associated Press Writer

ST. PAUL, Minn. (AP) -- On the slaughterhouse floor at Quality Pork Processors Inc. is an area known as the "head table," but not because it is the place of honor. It is where workers cut up pigs' heads and then shoot compressed air into the skulls until the brains come spilling out.

But now the grisly practice has come under suspicion from health authorities.

Over eight months from last December through July, 11 workers at the plant in Austin, Minn. - all of them employed at the head table - developed numbness, tingling or other neurological symptoms, and some scientists suspect inhaled airborne brain matter may have somehow triggered the illnesses.

The use of compressed air to remove pig brains was suspended at Quality Pork earlier this week while authorities try to get to the bottom of the mystery.

"I'm still in shock, I guess," said 37-year-old Susan Kruse, who worked at the plant for 15 years until she got too weak to do her job last February. "But it was very surprising to hear that there was that many other people that have gotten this."

Five of the workers - including Kruse, who has been told she may never work again - have been diagnosed with chronic inflammatory demyelinating polyneuropathy, or CIDP, a rare immune disorder that attacks the nerves and produces tingling, numbness and weakness in the arms and legs, sometimes causing lasting damage.

New cases of CIDP occur at the rate of one or two per 100,000 people each year, according to Dr. P. James B. Dyck of the Mayo Clinic.

State health officials said there is no evidence the public is at risk - either from those afflicted or from any food leaving the plant, which supplies Hormel Foods Inc.

The working theory from two Mayo Clinic neurologists treating the workers: Exposure to pig brain tissue scattered by the compressed air triggered the illnesses.

"As we've investigated these patients, we have information that suggests very strongly that the immune system is activated very strongly in a very compelling way," said Dr. Daniel Lachance.

Compressed air could turn some brain matter into a mist that could be inhaled by workers, said Mike Doyle, a microbiologist who heads the University of Georgia's Center for Food Safety. Or the workers may have come into contact with something dangerous and then touched their noses or mouths, he said.

Scientists have yet to figure out if there is something in the brain matter that could be causing the symptoms.

"The hard part will be identifying the causative agent and associating that with the animal, showing that the animal carries it," Doyle said.

Minnesota Health Department spokesman Doug Schultz said the agency is looking into the theory but has not ruled out other causes. Kruse said the company has harvested pork brains on and off for years, depending on demand, but it's not known why workers began getting sick recently.

Quality Pork has not said what it does with the pork brains. Sold fresh and in cans, pork brains are fried and eaten in sandwiches or gravy in some parts of the country. But it is a small market, and the American Meat Institute, which represents most of the nation's pork processors, does not even track sales.

Exactly how many of the plant's 1,300 employees worked at the head table is unclear; Quality Pork's chief executive did not return calls. Kruse said there were 11 workers at the head table on any given shift, but the lineup changed because of turnover or because people were assigned other jobs.

In a rapid-fire process that is noisy, smelly and bloody, severed pigs' heads are cut up at the head table at a rate of more than 1,100 an hour. Workers slice off the cheek and snout meat, then insert a nozzle in the head and blast air inside until the light pink mush that is the brain tissue squirts out from the base of the skull.

Kruse, whose job was to remove meat from the back of the animals' heads, said she doesn't recall any spray or mist from the de-braining. The head-table workers were protected by safety glasses, helmets, gloves and belly guards, but none wore anything over their mouths or noses, she said.

Head-table workers are now required to wear plastic face shields and protective plastic or rubber sleeves, the Health Department said.

The use of compressed air to remove hog brains is relatively uncommon, according to industry officials. That's because many plants don't even remove them. And some of the processors that do extract brains simply split the hogs' skulls open.

Some of the biggest pork processors - Tyson Foods Inc., JBS Swift & Co. and Cargill Inc. - said they don't handle brains because the market isn't big enough. No pork workers at Tyson, Cargill or JBS Swift have reported symptoms similar to those of the Quality Pork employees, the companies said.

CIDP attacks the lining around the nerves, slowing or blocking the brain's signals to the muscles. But exactly what triggers the attack is unknown.

Victims can recover fairly quickly if the illness is caught early, said Dr. Kenneth Gorson, a neurologist at St. Elizabeth's Medical Center in Boston.

In advanced cases, treatment arrests the disease but doesn't reverse its effects, he said. Treatment involves infusions of immune globulin or a plasma-exchange technique that removes antibodies from the patient's blood. Another option is a steroid called prednisone.

American Meat Institute spokeswoman Janet Riley said: "We are watching the situation very closely and we've offered any help that the state health department would need. But certainly if facts came to light that justified the change in practices, you could imagine protecting the workers is critical."

Workers are worried, said Richard Morgan, who heads the union local at Quality Pork.

"The process has stopped, where they assume it was at," he said. "It could have been from something different. Nobody knows at this time. We can talk about gray matter till we're blue in the face."