BEIJING (AP) -- China's military on Tuesday denied renewed U.S. accusations that it sponsored cyberattacks and said the two sides should cooperate against the global threat of computer crime.

The accusations in the latest Pentagon report on the Chinese military are "irresponsible and harmful to the mutual trust between the sides," Senior Col. Wang Xinjun, a People's Liberation Army researcher, was quoted by the official Xinhua News Agency as saying.

"The Chinese government and armed forces have never sanctioned hacking activities," said Wang, who is based at the Academy of Military Sciences in Beijing, one of the PLA's main think tanks. The military frequently uses such academics as alternative spokesmen.

The annual Pentagon report released Monday included for the first time the accusation that at least some attacks on U.S. government and other computer systems appeared to be "attributable directly" to the Chinese government and military. It said China is using its cyber capabilities to collect intelligence against U.S. diplomatic, economic and defense programs, and is developing the skills needed to conduct cyberwarfare.

The new wording in the report continues an escalating effort by U.S. officials to call out the Chinese on the cyberattacks and to press for a more open dialogue with Beijing on the problem.

Chinese Foreign Ministry spokeswoman Hua Chunying reiterated that China opposes cyberattacks as well as "all groundless accusations and hyping" that could harm prospects for cooperation.

"We are willing to hold even-tempered and constructive dialogue with the U.S." about cybercrime, Hua said.

The issue was spotlighted in February with the issuing of a report by U.S.-based cybersecurity firm Mandiant that claimed to have traced several years of cyberattacks against 140 mostly American companies to a Chinese military unit in Shanghai. Mandiant executives say attacks originating in China have continued since then, with the exception of those from Shanghai-based Unit 61398 that had been highlighted in its earlier report.

China says it's impossible to tell the true origin of cyberattacks, and accuses hostile forces in the U.S. and elsewhere of blaming China out of prejudice or a desire to put Beijing on the defensive.

It has also called on the sides to join forces against cyber criminals, and officials earlier this year agreed to set up a joint working group on cybercrime.

"Both China and the U.S. are victims of cybercrimes and should work together to tackle the problems," Xinhua cited Wang as saying.

He received 62 first-place votes and 404 points in balloting by 121 sportswriters and broadcasters in the United States and Canada.

Miami's Eric Spoelstra finished second. He was followed by New York Knicks coach Mike Woodson, San Antonio's Gregg Popovich and Indiana's Frank Vogel.

The coach of the year award is Karl's first in 25 NBA seasons. The only other Nuggets coach to receive the honor is Doug Moe.

Karl, who left the sideline several years ago to battle cancer, guided the Nuggets to a team-record 57 victories and the No. 3 playoff seed in the Western Conference as Denver reached the postseason for the 10th consecutive year.

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The injury-ravaged Chicago Bulls ruled out forward Luol Deng for Game 2 of their Eastern Conference playoff series with the Miami Heat on Wednesday night and listed guard Kirk Hinrich as doubtful.

Deng is still not with the team. He remains in Chicago while recovering from an illness that sent him to the hospital last week for a spinal tap. Hinrich continued to be slowed by a calf injury.

Hinrich has not played since Chicago's triple-overtime win in Game 4 of the first-round series with the Brooklyn Nets. Thibodeau said Hinrich's condition is improving and he remains day to day. (Editing by Frank Pingue)

First, there was what felt like a million questions. "What kind of dress was I looking for? What size am I? What kind of color? Long or short?" said the 15-year-old freshman at Mount Edgecumbe High School, a state-run boarding school in Sitka, Alaska.

Her answers gave her passage into a room stocked full of dresses a bounty that Kayla, or most students, in rural Alaska have never seen.

The dresses were brought to the school by the Seattle-based Prom Princess program, which brings the prom experience to Mount Edgecumbe, where many students don't have the resources or the help from their far-off families to get party dresses, tuxedos and makeup for their big night.

"All of these people are here helping them (the students) out and doing all this stuff, and suddenly they realize they're a lot more important than they ever thought they were," said Ivy Lanthier, project director for the school's dorms. "That's the big thing."

In its fifth year of helping students at the school, the program arranges for donations of the dresses, discounted tuxes, and hair and makeup artists.

Mount Edgecumbe, which sits in the shadow of a dormant volcano, is the only state-run boarding school in Alaska. It has nearly 400 students, and about 80 percent this year are Alaska Native. Many, like Kayla, hail from small communities well off the state's limited road system. Many schools in these rural villages don't have proms, and ones that do aren't at Mount Edgecumbe's level.

Program founder Terri Bogren said she and other volunteers, mainly her co-workers at the Seattle-based Alaska Airlines, are proud of the teenagers for leaving their families and villages to get a better education, and this is a way to show their admiration.

"They don't have the family support to help them do this. So we're kind of like fairy godmothers here to help them make sure they can look as good as they want to go to their prom," she said.

Bogren got the idea for the program when she lived in Sitka and helped a niece, who was attending the school, get ready for the prom. That's when she realized other girls weren't going to the dance because they didn't have a dress.

Bogren moved to Seattle after she got a job as an account specialist with the airline, which had just celebrated its 75th anniversary in 2007. She decided to see if anyone would be willing to donate her party dress from the anniversary ball for the girls at Mount Edgecumbe.

"I know lots of people buy expensive dresses and only wear them once," she said. "So I figured this would be a good opportunity to ask for donations."

That first year, 30 dresses were donated. That number has increased to about 130 this year, and the girls get to keep the frocks they pick.

The main booster for the program, Bogren solicits donations while talking to people on airplanes, in airports, at work. The program has a signature identifier: During the prom, all the volunteers wear tiaras, but Bogren sports one throughout the year to attract attention to her program.

The number of volunteers also has grown, from Bogren and five others the first year to about 40 this year. The volunteers are Alaska Airlines or Horizon Air employees, and their family and friends from across the Pacific Northwest. The volunteers include professional hairdressers, nail artists, even a master tailor.

Last Saturday, they gave the girls up-dos, fancy nails, took prom photos and made flower decorations.

Like many students, sophomore Jessica Mute was appreciative for the help. She spent the day primping for the all-school prom, but also found time to make her boyfriend a boutonniere. Mute said it was especially nice since the boarding students "have no parents or moms" there to help them.

For many, Saturday's prom was the first time they have dressed formally for a dance, had clothes altered, had their nails and hair done, got tanning, even wore jewelry. "It's something that many of them have seen on TV," Lanthier said. "They know other people do it, and now they're doing it."

Kellie Oester, a Portland, Ore.-based flight attendant who was in Sitka for the second year, said the freshman girls "touched my heart."

"I have a daughter that is 17. I think, 'Oh, it would be hard for her to be away from home.' So I think they kind of get the nurturing from us," said Oester, who described her duty as "glam fairy," spraying girls with glitter.

And for the record, Kayla picked a dress that was black on the top with white frilly ruffles on the bottom. She planned to wear it when she and friends went to a pizzeria before the dance. "I'm just going to be extra careful" not to drop any food on it, she laughed.

They say Prime Minister Hesham Kandil's three-car convoy was on a Cairo bridge late Sunday when it encountered the speeding truck, and fired warning shots in the air to get it to move.

The men fired birdshot at the convoy. They later told police they didn't realize the prime minister was inside one of the tinted-windowed cars.

The men were promptly arrested. Police said they had apparently been racing to their home neighborhood after getting into a fight with people elsewhere.

Police officials, who spoke anonymously because they were not authorized to speak to the press, say the incident was not politically motivated.

WASHINGTON (AP) -- It's not a "Star Trek" tricorder, but by hooking a variety of gadgets onto a smartphone you could almost get a complete physical without the paper gown or even a visit to the doctor's office.

Blood pressure? Just plug the arm cuff into the phone for a quick reading.

Heart OK? Put your fingers in the right spot, and the squiggly rhythm of an EKG appears on the phone's screen.

Plug in a few more devices and you could have photos of your eardrum (Look, no infection!) and the back of your eye, listen to your heartbeat, chart your lung function, even get a sonogram.

If this sounds like a little too much DIY medical care, well, the idea isn't to self-diagnose with Dr. iPhone. But companies are rapidly developing miniature medical devices that tap the power of the ubiquitous smartphone in hopes of changing how people monitor their own health.

"We wanted to make sure they have all the right tools available in their pocket" is how Joseph Flaherty of AgaMatrix describes his company's tiny glucose monitor. Diabetics can plug the iBGStar into the bottom of an iPhone and check blood sugar on the go without carrying an extra device.

This mobile medicine also might help doctors care for patients in new ways. In March, prominent San Diego cardiologist Eric Topol tweeted "no emergency landing req'd" when he used his smartphone EKG to diagnose a distressing but not immediately dangerous irregular heartbeat in a fellow airplane passenger at 30,000 feet.

And the University of California, San Francisco, hopes to enroll a staggering 1 million people in its Health eHeart Study to see whether using mobile technology, including smartphone tracking of people's heart rate and blood pressure, could help treat and prevent cardiovascular disease.

The question: Do smartphone devices really work well enough for the average patient and primary care doctor to dive in, or are early adopters just going for the cool factor? Many of the tools cost $100 to $200, there's little public sales information yet and it's not clear how insurers will handle the fledgling trend.

"Technology sometimes evolves faster than we're ready for it," cautioned Dr. Glen Stream of the American Academy of Family Physicians. "We're recognizing more and more that not all care needs to be delivered face to face," but only if people measure the right things and have a relationship with a doctor to help make good use of the findings, he stressed.

Addressing a recent TEDMED conference in Washington, Dr. Susan Desmond-Hellmann, UCSF's chancellor, put the challenge this way: "How does mobile monitoring become something more than a toy or something interesting? How does it connect to how I'm cared for by my caregiver?"

About 300 doctors, health policy wonks and others attending that high-tech meeting received what was dubbed a "smartphone physical" from medical students using 10 of the latest devices. The Food and Drug Administration has approved a number of the gadgets for sale; others are experimental prototypes gathered for the demonstration by Nurture by Steelcase and the doctor website Medgadget.

"It's going to be our generation that adopts most of these," noted Shiv Gaglani, a Johns Hopkins medical student who helped organize the project.

The FDA cites industry estimates that 500 million smartphone users worldwide will use some type of health app by 2015. Today's apps mostly are educational tools, digital health diaries or reminders and fitness sensors. The new trend is toward more sophisticated medical apps, some that work with plug-in devices, that provide information a doctor might find useful.

Some of the devices sell by prescription or on drugstore shelves, while others like the diabetes monitor and blood pressure cuff have entered a new venue for medicine the Apple store.

Simplicity is part of the idea. Take the AliveCor Heart Monitor. Snap it on like a smartphone case, place fingers on the sensors no sticky wires on the chest and you've got an EKG recording in 30 seconds. The FDA approved sale of the $199 device in December for doctors to use in exams or to prescribe for patients to use on themselves.

It doesn't measure as much as a full-scale EKG, and patients must email the recording to a doctor for analysis. But heart patients frequently experience palpitations that have ended by the time they reach a cardiologist and emailing an on-the-spot EKG reading might help the doctor figure out what happened, said AliveCor co-founder Dr. Dave Albert.

"This is a brand-new technology. We're trying to understand how people will use it," said Albert, whose company also is seeking FDA permission to sell the device over the counter.

Welch Allyn's iExaminer taps the smartphone's camera to photograph deep inside the eye the orange view of the retina filling the phone's screen.

Similarly, CellScope Inc. is developing an otoscope that magnifier doctors use to peer into the ear that can snap a photo of the eardrum. It's not for sale yet, but might parents one day email that kind of picture to the pediatrician before deciding whether Johnny needs an office visit?

"It was great to see it on the phone, rather than the pinpoints we get to see" through a traditional scope, said Dr. Bertina Yen, a Los Angeles internist-turned-health IT specialist. She turned the tables during her smartphone physical, taking over some of the equipment to try it out herself.

And University of Washington researchers are testing a way to measure lung function in people with asthma or emphysema as they blow onto the phone and it captures the sound. Usually patients blow into special machines at the doctor's office, while a use-anywhere version might help someone spot early signs of worsening before they see a doctor.

Insurers are studying what smartphone technology to pay for. For example, health care giant Kaiser Permanente is about to begin a project in Georgia to sell the iBGStar alongside other diabetes monitors in its on-site pharmacies. The project will determine whether patients like the smartphone monitor, if it improves care and if so, whether the readings should beam into patients' electronic health records, in Georgia and in other Kaiser regions.

But ultimately these devices may have a bigger role in developing countries, where full-size medical equipment is in short supply but smartphones are becoming common. Even in rural parts of the U.S. it can take hours to drive to a specialist, while a primary care physician might quickly email that specialist a photo of, say, a diseased retina first to see whether the trip's really necessary.

"These tools make diagnosis at a distance much easier," said Dr. Nicholas Genes, an emergency medicine professor at New York's Mount Sinai School of Medicine, who helped with TEDMED's smartphone physical.

After settling near the rear of the field in the sloppy conditions, Orb steadily worked his way into contention, then pinned back his ears and sprinted to the front at the iconic Twin Spires and kicked clear to win the $2 million, 1-1/4 mile classic.

Golden Soul, a long shot who enjoyed a trouble free journey along the rails, finished gamely to grab second while Revolutionary was third in the 19-horse field.

"It's awesome, to win the Derby, it's like a dream," said Rosario, who had never won the Derby before but won this year's $10 million Dubai World Cup, the world's richest race, on Animal Kingdom.

"I was so far behind I just let (Orb) be calm and relaxed, then I steered him to the outside because I didn't want to get blocked. He did the rest."

Normandy Invasion finished fourth after leading the field into the final stretch while Mylude was fifth under the guidance of Rosie Napravnik, marking the best finish in the revered race by a female jockey.

Orb, who was bred and trained in Kentucky, emerged as the horse to beat in the annual Run for the Roses after winning his four previous races, including the $1 million Florida Derby, one of the key lead-up events.

He was initially installed as the 7-2 favorite despite drawing gate 16 at Wednesday's post-position draw but began to drift in the betting as the race approached.

Only a late surge of money saw him retain his place as outright favorite, at odds of 5-1, just a point ahead of Revolutionary, the Louisiana Derby winner.

HUGE THRILL

"Obviously it's a huge, huge thrill for me," said McGaughey, a 62-year-old trainer who was born and raised in Kentucky.

"It's a race I've always wanted to win, a race I've always wanted to compete in if I thought I had the right horse, and finally today we had the right horse."

McGaughey had already won most of America's biggest races and been inducted into the Hall of Fame almost a decade ago, but the Kentucky Derby had always eluded him.

"I don't know what it will be like tomorrow morning when I pinch myself and figure all this out," he said.

"The way it's going to change my life is I'm not going to have to worry about it anymore, because I've worried about it for a while."

Rosario, a 28-year-old jockey born in Dominican Republic, patiently held his mount back in the early stages of the race, which was held on a track drenched by hours of heavy rain.

He resisted the temptation to look for a shortcut on the fence, opting instead to keep Orb on the outside, where he continued to make ground.

It was a tactic that paid off when the early leaders, who had set off at a cracking pace, started to fade, Orb was perfectly positioned to make his charge.

DEAFENING ROAR

Orb swept past a dozen rivals on the back straight and was within sight of the leaders round the final turn. As the crowd of 151,616 let out a deafening roar, he made his move, charging down the center of the track and holding off all his challengers.

Golden Soul, a 31-1 chance ridden by Robby Albarado, also came from behind to take second for his owner, Canadian diamond magnate Charles Fipke.

Revolutionary was one of five runners in the race trained by Todd Pletcher. He was ridden by Calvin Borel, a three-time winner of the Kentucky Derby, who stuck to the fence but could catch the winner.

The lone international entrant, Irish galloper Lines of Battle, finished seventh, while Goldencents (7-1), prepared by last year's winning trainer Doug O'Neill, weakened badly to cross the line 17th under jockey Kevin Krigger, who was bidding to become the first African-American jockey to win the race in more than a century.

In keeping with tradition, the race was preceded by the singing of "My Old Kentucky Home" as a huge crowd packed into the Louisville course, dressed in an array of outfits and sipping on mint julep drinks.

But no sooner had Orb, who paid $12.80 for a $2 bet, been draped in the traditional garland of red roses, than talk turned to the future.

The bay colt now has the chance to win the coveted Triple Crown. The second leg, the Preakness Stakes, will be held at Maryland later this month followed by the Belmont Stakes, in New York in June.

The last horse to win the Triple Crown was Affirmed in 1978.

"I still think there's something more there, I don't think we've bottomed out," said McGaughey. "I think we've got our hands on a pretty special horse."

(Reporting by Julian Linden in New York, editing by Gene Cherry)

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In U.S. hospitals, an estimated 1 in 20 patients pick up infections they didn't have when they arrived, some caused by dangerous 'superbugs' that are hard to treat.

The rise of these superbugs, along with increased pressure from the government and insurers, is driving hospitals to try all sorts of new approaches to stop their spread:

Machines that resemble "Star Wars" robots and emit ultraviolet light or hydrogen peroxide vapors. Germ-resistant copper bed rails, call buttons and IV poles. Antimicrobial linens, curtains and wall paint.

While these products can help get a room clean, their true impact is still debatable. There is no widely-accepted evidence that these inventions have prevented infections or deaths.

Meanwhile, insurers are pushing hospitals to do a better job and the government's Medicare program has moved to stop paying bills for certain infections caught in the hospital.

"We're seeing a culture change" in hospitals, said Jennie Mayfield, who tracks infections at Barnes-Jewish Hospital in St. Louis.

Those hospital infections are tied to an estimated 100,000 deaths each year and add as much as $30 billion a year in medical costs, according to the Centers for Disease Control and Prevention. The agency last month sounded an alarm about a "nightmare bacteria" resistant to one class of antibiotics. That kind is still rare but it showed up last year in at least 200 hospitals.

Hospitals started paying attention to infection control in the late 1880s, when mounting evidence showed unsanitary conditions were hurting patients. Hospital hygiene has been a concern in cycles ever since, with the latest spike triggered by the emergence a decade ago of a nasty strain of intestinal bug called Clostridium difficile, or C-diff.

The diarrhea-causing C-diff is now linked to 14,000 U.S. deaths annually. That's been the catalyst for the growing focus on infection control, said Mayfield, who is also president-elect of the Association for Professionals in Infection Control and Epidemiology.

C-diff is easier to treat than some other hospital superbugs, like methicillin-resistant staph, or MRSA, but it's particularly difficult to clean away. Alcohol-based hand sanitizers don't work and C-diff can persist on hospital room surfaces for days. The CDC recommends hospital staff clean their hands rigorously with soap and water or better yet, wear gloves. And rooms should be cleaned intensively with bleach, the CDC says.

Michael Claes developed a bad case of C-diff while he was a kidney patient last fall at New York City's Lenox Hill Hospital. He and his doctor believe he caught it at the hospital. Claes praised his overall care, but felt the hospital's room cleaning and infection control was less than perfect.

"I would use the word 'perfunctory,'" he said.

Lenox Hill spokeswoman Ann Silverman disputed that characterization, noting hospital workers are making efforts that patients often can't see, like using hand cleansers dispensers in hallways. She ticked off a list of measure used to prevent the spread of germs, ranging from educating patients' family members to isolation and other protective steps with each C-diff patient.

The hospital's C-diff infection rate is lower than the state average, she said.

Westchester Medical Center, a 643-bed hospital in the suburbs of New York City has also been hit by cases of C-diff and the other superbugs.

Complicating matters is the fact that larger proportions of hospital patients today are sicker and more susceptible to the ravages of infections, said Dr. Marisa Montecalvo, a contagious diseases specialist at Westchester.

There's a growing recognition that it's not only surgical knives and operating rooms that need a thorough cleaning but also spots like bed rails and even television remote controls, she said. Now there's more attention to making sure "that all the nooks and crannies are clean, and that it's done in perfect a manner as can be done," Montecalvo said.

Enter companies like Xenex Healthcare Services, a Texas company that makes a portable, $125,000 machine that's rolled into rooms to zap C-diff and other bacteria and viruses dead with ultraviolet light.Xenex has sold or leased devices to more than 100 U.S. hospitals, including Westchester Medical Center.

The market niche is expected to grow from $30 million to $80 million in the next three years, according to Frost & Sullivan, a market research firm.

Mark Stibich, Xenex's chief scientific officer, said client hospitals sometimes call them robots and report improved satisfaction scores from patients who seem impressed that the medical center is trotting out that kind of technology.

At Westchester, they still clean rooms, but the staff appreciates the high-tech backup, said housekeeping manager Carolyn Bevans.

"We all like it," she said of the Xenex.

At Cooley Dickinson Hospital, a 140-bed facility in Northampton, Mass., the staff calls their machines Thing One, Thing Two, Thing Three and Thing Four, borrowing from the children's book "The Cat in the Hat."

But while the things in the Dr. Seuss tale were house-wrecking imps, Cooley Dickinson officials said the ultraviolet has done a terrific job at cleaning their hospital of the difficult C-diff.

"We did all the recommended things. We used bleach. We monitored the quality of cleaning," but C-diff rates wouldn't budge, said nurse Linda Riley, who's in charge of infection prevention at Cooley Dickinson.

A small observational study at the hospital showed C-diff infection rates fell by half and C-diff deaths fell from 14 to 2 during the last two years, compared to the two years before the machines.

Some experts say there's not enough evidence to show the machines are worth it. No national study has shown that these products have led to reduced deaths or infection rates, noted Dr. L. Clifford McDonald of the Centers for Disease Control and Prevention.

His point: It only takes a minute for a nurse or visitor with dirty hands to walk into a room, touch a vulnerable patient with germy hands, and undo the benefits of a recent space-age cleaning.

"Environments get dirty again," McDonald said, and thorough cleaning with conventional disinfectants ought to do the job.

Beyond products to disinfect a room, there are tools to make sure doctors, nurses and other hospital staff are properly cleaning their hands when they come into a patient's room. Among them are scanners that monitor how many times a health care worker uses a sink or hand sanitizer dispenser.

Still, "technology only takes us so far," said Christian Lillis, who runs a small foundation named after his mother who died from a C-diff infection.

Lillis said the hospitals he is most impressed with include Swedish Covenant Hospital in Chicago, where thorough cleanings are confirmed with spot checks. Fluorescent powder is dabbed around a room before it's cleaned and a special light shows if the powder was removed. That strategy was followed by a 28 percent decline in C-diff, he said.

He also cites Advocate Christ Medical Center in Oak Lawn, Ill., where the focus is on elbow grease and bleach wipes. What's different, he said, is the merger of the housekeeping and infection prevention staff. That emphasizes that cleaning is less about being a maid's service than about saving patients from superbugs.

"If your hospital's not clean, you're creating more problems than you're solving," Lillis said.

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Freddie Mac said Thursday the average rate on the 30-year fixed mortgage fell to 3.89 percent. That's below the previous record of 3.91 percent reached three weeks ago.

Records for mortgage rates date back to the 1950s.

The average on the 15-year fixed mortgage ticked down to 3.16 percent. That's down from a record 3.21 percent three weeks ago.

Mortgage rates are lower because they track the yield on the 10-year Treasury note, which fell below 2 percent. They could fall even lower this year if the Fed launches another round of bond purchases, as some economists expect.

Average fixed mortgage rates hovered around 4 percent at the end of 2011. Yet many Americans either can't take advantage of the rates or have already done so.

High unemployment and scant wage gains have made it harder for many people to qualify for loans. Many don't want to sink money into a home that they fear could lose value over the next few years.

Mortgage applications have fallen slightly on a seasonally adjusted basis over the past four weeks, according to the Mortgage Bankers Association.

Frank Nothaft, Freddie Mac's chief economist, said that until hiring picks up and unemployment drops significantly, the impact of lower mortgage rates will remain muted.

Previously occupied homes are selling just slightly ahead of 2010's dismal pace. New-home sales in 2011 will likely be the worst year on records going back half a century.

Builders hope that the low rates could boost sales next year. Low mortgage rates were cited as a key reason the National Association of Home Builders survey of builder sentiment rose in December to its highest level in more than a year.

But so far, they have had little impact on the depressed housing market.

To calculate the average rates, Freddie Mac surveys lenders across the country Monday through Wednesday of each week. The average rates don't include extra fees, known as points, which most borrowers must pay to get the lowest rates. One point equals 1 percent of the loan amount.

The average fee for the 30-year loan fell to 0.7 from 0.8; the average on the 15-year fixed mortgage was unchanged at 0.8.

For the five-year adjustable loan, the average rate declined to 2.82 percent from 2.86 percent. The average on the one-year adjustable loan fell to 2.76 percent from 2.80 percent.

The average fee on the five-year adjustable loan rose was unchanged at 0.7; the average on the one-year adjustable-rate loan was unchanged at 0.6.

Both meteorites were found in Antarctica, and appear to date from before the solar system was born 4.6 billion years ago. Each contains a single grain of silica (SiO2, which is the main ingredient of sand). The chemical signature of these grains is identical, and extremely rare so rare, in fact, that scientists suspect both grains came from a single supernova. This type ofoccurs when a massive star runs out of fuel for nuclear fusion and collapses in on itself in a giant explosion.

These are the first such , and are distinct because of the type of oxygen contained in the silica. Previous research has uncovered a handful of space rocks containing silica grains enriched in oxygen-17, which is thought to be created by living stars. But a slightly heavier version of oxygen, called oxygen-18, was found in these two new grains. Oxygen-18 must be formed in a supernova. []

The silica grains are so small they are invisible to the naked eye. Using an instrument called a NanoSIMS 50 ion microprobe, which magnifies objects 20,000 times, graduate student Pierre Haenecour of Washington University in St. Louis uncovered the single grain in one of the meteorites. The other was found by Xuchao Zhao, now a scientist at the Institute of Geology and Geophysics in Beijing, China, inside a meteorite discovered by the Chinese Antarctic Research Expedition.

Haenecour investigated just how the silica grains might have come to be, and found that their formation would have required a complex process of mixing material from various different layers of the star as it exploded.

Because the precise mixing required to create oxygen-18 is so specific, the researchers suspect that both silica grains originated in the same supernova. That supernova might even be the same , the researchers speculated. Scientists think a shock wave from a supernova might have been the event that caused a rotating cloud of gas and dust to condense, eventually giving rise to the planets of our solar system.

As it exploded, the supernova also would have seeded the cloud with material, and some of that material may have ended up in the meteorites we find today.

The research is detailed in a paper published in the May 1 issue of Astrophysical Journal Letters.

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