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WASHINGTON, Aug. 10 (Xinhua) -- After a journey of almost three years, NASA's Mars rover Opportunity has reached the Red Planet's Endeavour crater to study rocks never seen before, the U.S. National Aeronautics and Space Administration (NASA) announced on Wednesday.Scientists hope it will find rocks and terrain much older than any other that the itinerant robot has examined during its seven years on the red planet.The U.S. space agency said that Opportunity arrived at the rim of Endeavour on Tuesday. The golf cart-size rover is expected to remain at the 22-kilometer-wide crater for the next few years.A portion of the west rim of Endeavour crater sweeps southward in this color view from NASA's Mars Exploration Rover Opportunity."NASA is continuing to write remarkable chapters in our nation' s story of exploration with discoveries on Mars and trips to an array of challenging new destinations," NASA Administrator Charles Bolden said in a statement. "Opportunity's findings and data ... will play a key role in making possible future human missions to Mars and other places where humans have not yet been."NASA's Mars Reconnaissance Orbiter, which has been circling the planet since late 2005, detected clay minerals that form in wet conditions in the crater. Scientists want to find out if the minerals date back to Mars' distant past, when the planet is believed to have been wetter and warmer than the dry frozen desert it is today."We're soon going to get the opportunity to sample a rock type the rovers haven't seen yet," said Matthew Golombek, Mars Exploration Rover science team member, at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "Clay minerals form in wet conditions so we may learn about a potentially habitable environment that appears to have been very different from those responsible for the rocks comprising the plains."NASA is searching for signs that Mars had a habitable environment billions of years ago. Knowledge of the Martian climate will be important to future manned missions there, and can shed light on the forces that shaped Earth's climate.NASA launched the Mars rovers Opportunity and Spirit in 2003 for what were planned to be three-month missions. But both continued operating well beyond that. Spirit stopped communicating in March 2010.

CHICAGO, Aug. 25 (Xinhua) -- Gold futures on the COMEX Division of the New York Mercantile Exchange on Thursday bounced off the biggest drop since March 2008, as the weakness in stock market enhanced appeal of gold as a safe-have investment.The most active gold contract for Dec. delivery gained 5.9 U.S. dollars, or 0.3 percent, to 1,763.2 dollars per ounce. The metal suffered on Wednesday the biggest one-day drop since March 19, 2008.Market analysts said that gold extended losses in earlier trading, hit by a margin-requirement increase, but the drop in global stock market gave a push to the metal. Both Dow Jones industrial average and S&P 500 declined on Thursday after a 3-day rise as a government report showed U.S. jobless claims rose last week.Besides, market hearsay went that Germany might be next to get a sovereign-debt downgrade, adding to the positive tone on gold market. German equity market also suffered sharp drop in the day.Many market watchers remained long-term bullish attitude toward gold although they said the precious metal could correct further in the short term. A trader noted that the fundamental factors driving uncertainty and fears are all still there.Expectations are growing that the Federal Reserve Chairman Ben Bernanke would not provide any form of stimulus in a speech scheduled for Friday at a yearly gathering of central bankers in Jackson Hole.Silver for Sept. delivery also rose 1.583 dollars, or four percent, to 40.745 dollars per ounce. Platinum for Oct. delivery lost 3.9 dollars, or 0.2 percent, to 1822.4 dollars per ounce.

BEIJING, July 26 (Xinhuanet) -- Hong Kong scientists announced that they had determined the idea of time travel is impossible by proving nothing can travel faster than the speed of light.The finding is contained in a study done by a research team from Hong Kong University of Science and Technology. The study was published Monday in a scientific journal "Physical Review Letters" in the United States."The study, which showed that single photons also obey the speed limit c, confirms Einstein's causality, that is, an effect cannot occur before its cause," the university said on its website."By showing that single photons cannot travel faster than the speed of light, our results bring a closure to the debate on the true speed of information carried by a single photon." said Professor Du Shengwang, who led the study.The possibility of time travel was raised 10 years ago when scientists discovered the optical pulses in some specific medium might propagate information in a faster-than-light speed."Our findings will also likely have potential applications by giving scientists a better picture on the transmission of quantum information." Du said.

WASHINGTON, July 7 (Xinhua) -- Space shuttle Atlantis will soar into the sky Friday on NASA's 135th and final flight. Its scheduled return to Earth later this month will mark the end of NASA's 30-year space program.Since its onset with the launch of space shuttle Columbia, the program has been seen as a cheap, safe and reliable way for space exploration.Despite its great contributions to U.S. manned space flight, it has also left some grave and tragic lessons, making its termination inevitable.HIKING COSTSLaunched in 1972 by then President Richard Nixon, the shuttle program aimed to provide a new system of affordable space travel and proved to be NASA's most enduring project in its 50 years of existence.In 1981, shuttle Columbia made its first shuttle flight for two days. It was the ultimate hybrid and the first reusable spacecraft.Launched like a rocket and gliding back to Earth like an airplane, space shuttles not only can act as a space taxi to carry astronauts, but have the muscle of a long-distance trucker to haul heavy machinery.The spaceship boasts more than 3,500 subsystems and 2.5 million parts and is nine times faster than a speeding bullet as it climbs heavenward. That versatility, however, has translated into higher costs.NASA originally estimated the program would cost about 90 billion U.S. dollars. However, its actual cost stands at about 200 billion dollars, compared with the 151 billion dollars spent on Apollo which took Americans to the moon in 1969.In an article in Technology Review, John Logsdon, former head of the Space Policy Institute at George Washington University, drew a direct connection between the ravenous shuttle budget and the lack of other large advances in manned space flight."By operating the system for 30 years, with its high costs and high risk, rather than replacing it with a less expensive, less risky second-generation system, NASA compounded the original mistake of developing the most ambitious version of the vehicle," he wrote."The shuttle's cost has been an obstacle to NASA starting other major projects," he added.HIGH RISKIn terms of safety, the shuttles have never been as reliable as their designers had envisioned.On average, one out of every 67 flights ended up with fatal accidents. Based on the rate of deaths per million miles traveled, the space shuttle is 138 times riskier than a passenger jet.Seven astronauts onboard died when Challenger exploded about a minute after launch in 1986. Nearly two decades after the tragic blast, a new catastrophe descended when the shuttle Columbia disintegrated moments before landing in 2003, killing another seven spacemen.Again, the shuttle program was shelved for more than two years as NASA stepped up efforts to make it safer. But experts say the fundamental problem related to shuttles' safety cannot be solved due to their "birth defects.""It is in the nation's interest to replace the Shuttle as soon as possible," concluded the panel that investigated the 2003 Columbia accident.

BEIJING, July 26 (Xinhuanet) -- The breast cancer is more deadly to black women than to whites, a new study found.This finding was published online Monday on the "Journal of Clinical Oncology" in the United States.The study was done by the City of Hope, a Comprehensive Cancer Center in Duarte, California.The researchers collected data from more than 4,500 U.S. women in the 35-64 age group who were diagnosed with breast cancer.With the passing of  more than eight years, the researchers found the black women have a three times death rate than white women, after taking obesity and other diseases into account."It’s been long known that breast cancer in African-American women is a far less common disease than in white women. But when it occurs, it seems to be more aggressive and harder to treat," said Dr. Lisa Carey of the University of North Carolina’s Lineberger Comprehensive Cancer Center.But why the situations varied by race, scientists are still exploring the answer.

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