Science Tuesday - Plate Tectonics, Genetic Testing, and Water on a Saturn Moon?
One day after the magnitude 9.2 earthquake on March 27, 1964, a section of an Anchorage street was several feet higher than another section. It is still the most powerful earthquake ever in North America.
A '64 Quake Still Reverberates
By Henry Fountain, The New York Times, April 7, 2014
When a strong earthquake rocked northern Chile on April 1, scientists were quick with an explanation: It had occurred along a fault where stresses had been building as one of the earth’s crustal plates slowly dipped beneath another. A classic low-angle megathrust event, they called it.
Such an explanation may seem straightforward now, but until well into the 20th century, scientists knew relatively little about the mechanism behind these large seismic events. But that all changed when a devastating quake struck south-central Alaska on March 27, 1964, nearly 50 years to the day before the Chilean quake.
Studies of the great Alaskan quake - undertaken largely by a geologist who, when he began, knew little about seismology - revealed the mechanism by linking the observed changes in the landscape to what was then a novel theory, plate tectonics.
That theory, that the earth’s top layer consists of large tectonic plates that are moving and colliding, helps explain the formation of mountains, volcanoes and other land features, as well as the occurrence of earthquakes. The Chilean quake, which was measured at magnitude 8.2 and killed at least six people, happened where an oceanic plate, the Nazca, slides beneath a continental one, the South American, at a shallow angle.
But in 1964 plate tectonics had many doubters, and until the Alaska event and the work of the geologist, George Plafker of the United States Geological Survey, no one had made the connection between these plate movements and earthquakes.
“Plate tectonics was originally proposed as a kinematic theory - it was about displacements, movements and velocities,” said Arthur Lerner-Lam, deputy director of the Lamont-Doherty Earth Observatory, part of Columbia University. “The great accomplishment was to link earthquakes to those movements.”
The Alaskan quake, which struck the south-central part of the state late in the afternoon of Good Friday, was of magnitude 9.2, making it still the most powerful earthquake ever recorded in North America, and the second-most powerful in the world after a 1960 earthquake in Chile. The ground shook violently over a huge area for about four and a half minutes. More than 125 people died, Anchorage was heavily damaged, and much of the young state’s infrastructure was destroyed.
The quake spawned a tsunami that spread across the Pacific. But most of the deaths occurred in Alaskan coastal towns and villages that were hit by local tsunamis that were generated by slumping or landslides under water near the shore. Some areas were inundated even before the shaking stopped, and water heights reached 150 feet or more in some cases. In the port of Valdez, much of the waterfront quickly disappeared as the sediments it was built on turned to jelly and collapsed.
“This was during the Cold War,” said Peter J. Haeussler, a geologist with the geological survey in Anchorage. “There were an awful lot of people who thought a nuclear bomb had gone off.”
Dr. Plafker had previously done geological mapping in Alaska - to better understand the state’s resource potential, not its earthquake risk - and was in Seattle at a scientific meeting when the quake occurred. “They needed somebody to get up there and appraise what really happened,” said Dr. Plafker, who at 85 still goes to the survey’s office in Menlo Park, Calif., regularly and is involved in research. The agency sent him there a day later with two other scientists.
“It was the usual kind of thing that happens,” he said. “Whoever is nearest and knows something about the area is sent, and is just expected to know everything.”
By some estimates, an area two-thirds the size of California had been affected by the quake, and the scientists set about studying the changes. What they found was astounding: barnacle-covered rocks that had risen and were now high and dry.
“At first it wasn’t really clear,” Dr. Plafker said. “But these ones that are uplifted, the barnacles will desiccate and turn white - it’s almost like painting a line on the shoreline.”
Elsewhere, they saw forests that had dropped so much that the trees were below the high-tide line and were being killed by salt water.
“You can always find something that shows whether the area went up or down,” he said.
They were there for about a week on that first trip, and what they could not map themselves they learned by asking around. “Places where you don’t have any info, the next best thing is to ask the fishermen, and especially the clammers,” Dr. Plafker said. “They know where the tide is.”
Over all, an extensive stretch of the coast, including islands in Prince William Sound, had been lifted as much as 38 feet in some places, while along much of the Kenai Peninsula and Kodiak Island, a large area had subsided up to eight feet.
“We were trying to figure out whether those ups and downs had anything to do with how it happened,” said Dr. Plafker, who returned to the state for more field work that summer. “No one had ever seen this kind of deformation before.”
At the time, tectonic theory was being vigorously debated, as was evidence that the seafloor was spreading as new crust formed in the middle of the oceans. The question was what happened to this new crust; one theory was that the whole planet was growing slightly.
Many ideas, including plate movement, about what caused the quake were floated. One of the most prevalent explanations suggested that the quake had occurred where one plate was rotating past another. But if this were the case, Dr. Plafker said, there would have been evidence of a large vertical fault somewhere in the vast expanse of land that was deformed by the earthquake.
He knew from his fieldwork that such evidence did not exist. “I had the advantage of seeing the rocks,” he said.
Instead, Dr. Plafker explained the quake by proposing that plates were colliding, as tectonic theory would have it, and at a low angle. One plate was sliding gradually beneath another, creating a long shallow fault zone that rippled a huge area when it slipped. His idea not only accounted for all the uplift and subsidence, it also explained what was happening to the new crust that was being formed in the oceans. Rather than adding to the circumference of the earth, Dr. Plafker said, “it was being stuffed under the continental margins.”
Dr. Plafker’s great contribution was to recognize that the pattern of deformation and tectonic theory went together, Dr. Haeussler said. “It became very clear that the only thing that fit the data was this low-angle thrust idea,” he said.
Dr. Plafker was aided, Dr. Haeussler said, by the geography of southern Alaska. The area where the two plates meet - the Pacific plate is sliding, or subducting, beneath the North American - has islands and other landforms where the deformation could be observed. In most areas around the Pacific Rim, where most of the world’s megathrust quakes occur, the junction of the two plates is offshore. Usually all of the uplift, and most of the subsidence, occurs on the seafloor, out of view.
That was presumably the case with the April 1 Chilean quake, which was centered in the Pacific about 55 miles northwest of the port of Iquique. Mapping the uplift would probably require a seagoing expedition - something scientists may want to undertake, since the quake did not appear to be strong enough to relieve all the strain in that part of the plate junction, making another large quake likely.
Dr. Plafker agreed that the Alaskan geography worked in his favor. So did his initial lack of a full understanding of seismology.
“Basically, I worked in Alaska doing my same kind of thing - regional geology,” he said. “All the earthquake stuff just got kind of worked in as a little diversion.
“It was probably to my advantage, my ignorance of the whole game,” he added. “And my trust in the rocks and barnacles.”
Fearing Punishment for Bad Genes
By KIRA PEIKOFF, The New York Times, APRIL 7, 2014
About 700,000 Americans have had their DNA sequenced, in full or in part, and the number is rising rapidly as costs plummet - to $1,000 or less for a full genome, down from more than $1 million less than a decade ago.
But many people are avoiding the tests because of a major omission in the 2008 federal law that bars employers and health insurers from seeking the results of genetic testing.
The Genetic Information Nondiscrimination Act, known as GINA, does not apply to three types of insurance - life, disability and long-term care - that are especially important to people who may have serious inherited diseases. Sponsors of the act say that they were well aware of the omission, but that after a 14-year effort to write and pass the law, they had to settle for what they could get.
That leaves many patients who may be at risk for inherited diseases fearful that a positive result could be used against them.
They include Brian S., a 33-year-old surgical resident in Pennsylvania, who has a 50 percent chance of carrying a genetic mutation that causes Cadasil, a fatal neurological disorder that afflicts his mother. “I kind of want to get tested,” Dr. S. said, speaking on the condition that his last name and other identifying details be withheld. But because he wants to apply for life and long-term-care insurance, he has decided against it.
There is no way of knowing how many people fall into this category, but experts say such concerns are mounting.
“It was all moot a few years ago,” said Dr. James P. Evans, a professor of genetics at the University of North Carolina, Chapel Hill. “It’s suddenly now become real because people increasingly have access to what’s in their genomes.”
Dr. Robert C. Green, a genetics researcher at Harvard Medical School, studied the behavior of those who had recently learned they carried a genetic marker that predisposes them to early Alzheimer’s disease. They were five times as likely to buy long-term-care insurance as those in a control group.
But while patients seek the protection that insurance offers, many are concerned about the possibility of paying higher premiums or being denied coverage altogether because of the known existence of a dangerous mutation.
“The fear is potent in our society that insurance companies are asking,” Dr. Green said. “The No. 1, 2 and 3 issue that subjects are concerned about is, will they be discriminated against if this is in their medical record?”
Just three states - California, Oregon and Vermont - have broad regulations prohibiting the use of genetic information in life, long-term-care and disability insurance.
At least one insurer, the Northwestern Mutual Life Insurance Company, asks potential customers in Massachusetts about genetic testing - and stipulates that refusing to share results could lead to a declined application or an extra premium. Jean Towell, a spokeswoman, says applicants are told “out of fairness” that insurers have the right to decline coverage if any medical information is omitted.
“We think it’s best to have it all spelled out in black and white so buyers can make a well-informed decision,” she said.
At least for now, 12 other companies ask no explicit questions about genetic testing. But when Dr. Green asked company executives why not, he said, “at least one of them has told me, ‘We would do this, but we don’t want to be the first.' ”
Still, he added, “you can imagine a world where millions of people have this information, and that would reach a tipping point that the insurance companies can no longer ignore.”
Even if most insurers are not asking now, they do seek out medical records and can use genetic test results listed there. By contrast, under the federal law, an employer who asks for an employee’s records must tell the provider to withhold any genetic information.
Robin Bennett, a genetics counselor at the University of Washington, sees patients almost every day who express fears about how their test results might be used.
Some ask, “could we not put it in their medical records,” she said, “but they don’t realize that if we’re going to take action on their information” - such as preventive surgery to lower risk for breast cancer - “it has to be in their records.”
The American Medical Association’s code of ethics states that “it may be necessary” for doctors to maintain a separate file for genetic test results so the information is not sent to insurers. A study published last year by Dr. Robert L. Klitzman, who directs the Masters of Bioethics Program at Columbia University (in which this reporter is a student), found that 4.5 percent of 220 general internists admitted to hiding or disguising genetic information.
“With electronic medical records, it’s not clear what will happen,” he said. “Will it become impossible to hide certain kinds of data? Will there be a way to section some things off? A lot of this is still being worked out.”
But even if such results can be kept private, patients could be penalized. A life insurance broker for Accuquote, an online service that compares insurance policies, said that if an applicant carried a highly predictive marker for a disease like Alzheimer’s and failed to disclose it, that would be “guilt by omission.”
As the cost of sequencing falls, some experts worry that insurers may run their own tests on specimens they collect. Only one state, New Mexico, requires that applicants be informed of such tests.
Fear of discrimination affects research participants as well as patients. Dr. Green said that 23 out of 94 volunteers who walked away from a sequencing study did so because of concerns about insurance.
To recruit subjects who refuse genetic testing, Dr. Steven M. Hersch, a laboratory director at the MassGeneral Institute for Neurodegenerative Disease, designed a study to allow patients at risk for Huntington’s disease to participate in a clinical trial without being told their mutation status.
“Insurance fears play a big role,” he said. These worries, he added, are spreading to a growing community of people aware of predictive testing for hereditary illnesses like Alzheimer’s, breast cancer and colon cancer.
Not everyone is convinced that such discrimination is a major problem.
“There’s this theoretical risk,” said Dr. Leslie G. Biesecker, a chief investigator at the National Human Genome Research Institute, adding that he was not aware of anyone who had faced discrimination after participating in genetic research.
“Participants are more likely to be in serious car crash going to or from the research center,” he said.
But Dr. Klitzman, at Columbia, says genetic discrimination can be subtle.
“Someone may not know exactly why they were turned down,” he said. Or patients who have been discriminated against “may not go public because then they’d be letting everyone know they have X mutation.”
Consumer advocates say comprehensive federal legislation is needed to assure people they can safely participate in genetic research and testing.
“We are already late in the process of addressing this issue through public policy and law,” said Jeremy Gruber, president of the Council for Responsible Genetics. “The question is how soon are we going to realize that we need to act now.”
Insurance industry representatives, by contrast, argue that they may need genetic information to make underwriting decisions.
Barring long-term-care and life insurers from obtaining applicants’ test results “could lead to adverse selection and impact the stability of rates,” the American Academy of Actuaries said in a statement.
The author of the 2008 law, Representative Louise M. Slaughter, a Democrat from upstate New York, was noncommittal about any changes. “Given the rapid pace of technological innovation, the uncharted waters that we are navigating when it comes to genetic information, and the arduous, 14-year effort to finally pass GINA into law, we must be extremely judicious in our next steps,” she said.
As for Brian S., he and his wife want to have a baby. But because he has decided not to be tested for the fatal neurological disorder, they are considering in vitro fertilization with pre-implantation genetic diagnosis.
That would allow any embryos carrying the dreaded mutation to be silently screened out, keeping him ignorant of his own status - and able to apply for life and long-term-care insurance without fear of being turned down.
Enceladus as viewed from NASA’s Cassini spacecraft. Gravity measurements taken by the craft align with the presence of a sea 20 to 25 miles below the moon’s surface, scientists say.
Under Icy Surface of a Saturn Moon Lies a Sea of Water, Scientists Say
By KENNETH CHANG, The New York Times, APRIL 3, 2014
Inside a moon of Saturn, beneath its icy veneer and above its rocky core, is a sea of water the size of Lake Superior, scientists announced on Thursday.
The findings, published in the journal Science, confirm what planetary scientists have suspected about the moon, Enceladus, ever since they were astonished in 2005 by photographs showing geysers of ice crystals shooting out of its south pole.
“What we’ve done is put forth a strong case for an ocean,” said David J. Stevenson, a professor of planetary science at the California Institute of Technology and an author of the Science paper.
For many researchers, this tiny, shiny cue ball of a moon, just over 300 miles wide, is now the most promising place to look for life elsewhere in the solar system, even more than Mars.
“Definitely Enceladus,” said Larry W. Esposito, a professor of astrophysical and planetary sciences at the University of Colorado, who was not involved in the research. “Because there’s warm water right there now.”
Enceladus (pronounced en-SELL-a-dus) is caught in a gravitational tug of war between Saturn and another moon, Dione, which bends its icy outer layer, creating friction and heat. In the years since discovering the geysers, NASA’s Cassini spacecraft has made repeated flybys of Enceladus, photographing the fissures (nicknamed tiger stripes) where the geysers originate, measuring temperatures and identifying carbon-based organic molecules that could serve as building blocks for life.
Cassini has no instruments that can directly detect water beneath the surface, but three flybys in the years 2010-12 were devoted to producing a map of the gravity field, noting where the pull was stronger or weaker. During the flybys, lasting just a few minutes, radio telescopes that are part of NASA’s Deep Space Network broadcast a signal to the spacecraft, which echoed it back to Earth. As the pull of Enceladus’s gravity sped and then slowed the spacecraft, the frequency of the radio signal shifted, just as the pitch of a train whistle rises and falls as it passes by a listener.
Using atomic clocks on Earth, the scientists measured the radio frequency with enough precision that they could discern changes in the velocity of Cassini, hundreds of millions of miles away, as minuscule as 14 inches an hour.
They found that the moon’s gravity was weaker at the south pole. At first glance, that is not so surprising; there is a depression at the pole, and lower mass means less gravity. But the depression is so large that the gravity should actually have been weaker.
“Then you say, ‘A-ha, there must be compensation,’ ” Dr. Stevenson said. “Something more dense under the ice. The natural candidate is water.”
Liquid water is 8 percent denser than ice, so the presence of a sea 20 to 25 miles below the surface fits the gravity measurements. “It’s an ocean that extends in all directions from the south pole to about halfway to the equator,” Dr. Stevenson said.
The underground sea is up to six miles thick, much deeper than a lake. “It’s a lot more water than Lake Superior,” Dr. Stevenson said. “It may even be bigger. The ocean could extend all the way to the north pole.”
The conclusion was not a surprise, said Christopher P. McKay, a planetary scientist at NASA Ames Research Center in Mountain View, Calif., who studies the possibility of life on other worlds, but “it confirms in a really robust way what has been sort of the standard model.”
It also makes Enceladus a more attractive destination for a future mission, especially one that would collect samples from the plumes and return them to Earth to see if they contain any microbes.
The discussion on the possibility of extraterrestrial life in the solar system centers on four bodies: Mars; Enceladus; Europa, a moon of Jupiter; and Titan, another moon of Saturn.
Dr. McKay, who was not involved with gravity measurements, noted that only Enceladus was known to possess the four essential ingredients for life, at least as it exists on Earth: liquid water, energy, carbon and nitrogen.
“I would say it’s our best bet,” he said.
Mars has a dearth of nitrogen, found in amino acids and proteins, and the surface today is dry and cold. Europa, which also has an under-ice ocean, may have all of the ingredients, but that has not been confirmed. Ice plumes have also been observed coming off Europa’s south pole, but intermittently. Titan is the most intriguing and speculative possibility, with lakes of liquid methane, not water. If life existed there, it would be far different from that on Earth.
Still, life on Enceladus is perhaps a long shot. The sea is at freezing temperature and in continual darkness. And the water may have been liquid only in the recent past, a few tens of millions of years, a blink in the 4.5-billion-year history of the solar system. But scientists also do not know how long it takes life to get started, and some think it could happen quickly.
“Is there life in the plume?” Dr. McKay said. “To answer that question, a sample return would be the way.”
There are a couple of proposals for that already, including one by Peter Tsou, a retired scientist from NASA’s Jet Propulsion Laboratory. Dr. Tsou devised a way to capture comet particles and bring them back to Earth for NASA’s Stardust mission and has been suggesting a similar method for a spacecraft that would fly through Enceladus’s plumes and then return to Earth for scientists to examine.
The challenges are to make sure that the interesting particles would not break apart, to take precautions that any alien life would not infect Earth, and to fit it into the $500 million budget of one of NASA’s lower-cost planetary missions.