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WASHINGTON, Aug. 4 (Xinhua) -- Observations from NASA's Mars Reconnaissance Orbiter have revealed possible flowing water during the warmest months on Mars, the U.S. National Aeronautics and Space Administration (NASA) announced Thursday.Dark, finger-like features appear and extend down some Martian slopes during late spring through summer, fade in winter, and return during the next spring. Repeated observations have tracked the seasonal changes in these recurring features on several steep slopes in the middle latitudes of Mars' southern hemisphere."The best explanation for these observations so far is the flow of briny water," said Alfred McEwen of the University of Arizona, Tucson.McEwen is the principal investigator for the orbiter's High Resolution Imaging Science Experiment and lead author of a report about the recurring flows to be published in Friday's edition of the journal Science.Seven such sites on the planet have been confirmed, with 20 more possible, McEwen said."What makes these new observations so interesting is they occur at much lower latitudes where temperatures are much warmer and where it's actually possible for liquid water to exist," said Arizona State University geophysicist Phil Christensen, one of the scientists who studied the images beamed back from the orbiter.The study does not prove water exists, but identifies it as the best explanation. It's worthwhile to think about alternative reasons for these observations, but none seems to fit as well as briny water, McEwen said."I think it's going to be laboratory experiments on Earth that give us the best confirmation or refutation," he said.

WASHINGTON, July 12 (Xinhua) -- Two U.S. astronauts stepped out the International Space Station on Tuesday to retrieve a failed ammonia pump, which is the last spacewalk of the shuttle era, NASA announced.Space station astronauts Mike Fossum and Ron Garan completed the six-hour, 31-minute spacewalk at 3:53 p.m. EDT (1953 GMT). The duo retrieved a pump module from an external stowage platform on station and store it in shuttle Atlantis' cargo bay for return to Earth.The pump module failed in 2010, shutting down half of the space station's cooling system. Engineers will evaluate the module to determine the cause of the failure and plan to refurbish it for use as a spare.The astronauts also attached a Robotic Refueling Module experiment to the space station, which aims to test technologies for repairing and refueling satellites in space.It was the 249th spacewalk by U.S. astronauts and the 160th spacewalk in support of space station assembly and maintenance, totaling 1009 hours, nine minutes.Atlantis lifted off on Friday morning from Kennedy Space Center in Florida, on the 135th and final flight in NASA's shuttle program. Its return to the earth later this month will mark the end of the 30-year shuttle program.

BEIJING, Aug. 13 (Xinhua) -- Chinese rating agency Dagong Global Credit Rating Co. on Saturday defended its AAA rating given to the Ministry of Railways, which has been under public fire over a train collision last month.The ministry received the long-term credit rating after launching on Monday its first bond sales since the crash on July 23 that killed 40 people near the Wenzhou city of eastern Zhejiang province.It sold 20 billion yuan worth of three-month bills on offer in the interbank market, with a yield of 5.55 percent, a relatively high rate for short-term government paper.The rating was assigned because of the ministry's status as a government agency backed by the central government revenue, its sufficient capital flows and strong financing ability, Dagong said in an email to Xinhua.The agency made the elaboration in response to market doubts as the ministry is already heavily indebted and the accident has stirred up skepticism about the its credibility and the safety of fast-expanding railways.Adding to doubts is that the AAA rating of the ministry is even a notch above China's local currency debt rating of AA+, which was also rated by Dagong.Government data showed the ministry's debts exceeded 2 trillion yuan (313 billion U.S. dollars) as of the end of June, raising its debt ratio to 58.53 percent, slightly up from the end of the first quarter of this year.Dagong said in the statement that the debt-to-asset ratio is medium level, lower than the alert line for the ministry which is 75 percent.The ministry has large-scale assets of good quality and relatively large room for fund-raising, Dagong said.The ministry has "extremely strong" repayment ability as it is backed by the state's credit, Dagong said, referring it as one of the three authorities that are allowed to issue bonds, along with the Ministry of Finance and the People's Bank of China.In July, the ministry issued 20 billion yuan of one-year commercial papers with a coupon rate of 5.18 percent, but only 18.73 billion yuan of the total was bought.Analysts said it has become more difficult for the ministry to borrow money because of tightened market liquidity and concerns over the ministry's debt burden.China's top four banks said at the end of last month that they will continue to offer loans to the ministry based on market conditions and risk appraisal. Credit from the four largest state-owned banks including the Industrial and Commercial Bank of China and the Construction Bank of China has been the major source funding the construction of China's fast-growing railways in recent years.

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