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WASHINGTON, Dec. 21 (Xinhua) -- NASA's Dawn spacecraft has sent around 10,000 pictures of the giant asteroid Vesta back to Earth for the first time since its launch in 2007, the U.S. space agency announced Wednesday.The images were taken from an average altitude of 209 km, the closest the spacecraft can get.From the images, scientists could see Vesta's stippled and lumpy surface in great detail, and its many small craters, grooves, and lineaments. The fine scale of the images highlights small outcrops of bright and dark material.With these new discoveries, scientists believe that studying Vesta can help decode the early history of the solar system.Dawn will maintain its low-altitude orbit for another 10 weeks before moving to a higher orbit for another round of photo-taking.Launched in 2007, the 446 million U.S. dollar project aims at studying the chemical composition of Vesta's surface and probing its interior structure.Dawn will leave Vesta in July next year and arrive at the dwarf planet Ceres in February 2015.

BEIJING, Jan. 8 (Xinhua) -- China started the Spring Festival peak travel season Sunday, with tens of millions of passengers, mainly migrant workers and college students, on the move in the world's largest seasonal migration.The Spring Festival, or Chinese Lunar New Year, fall on Jan. 23 this year. It is the most important traditional Chinese festival for family reunions.A total of 3.16 billion passenger trips are expected during the 40-day peak travel season, or Chunyun (Spring transportation) in Chinese, up 9.1 percent from a year earlier, according to the National Development and Reform Commission.

WASHINGTON, Nov. 16 (Xinhua) -- Data from NASA's Galileo spacecraft have provided scientists evidence of what appears to be a body of liquid water, equal in volume to the North American Great Lakes, beneath the icy surface of Jupiter's moon, Europa, the U.S. space agency announced Wednesday.The data suggest there is significant exchange between Europa's icy shell and the ocean beneath. This information could bolster arguments that Europa's global subsurface ocean represents a potential habitat for life elsewhere in our solar system. The findings will be published Thursday in the scientific journal Nature.Europa, which is slightly smaller than Earth's moon, is believed to have a large ocean of salty water deep beneath its frozen crust. Galileo spacecraft, launched by the space shuttle Atlantis in 1989, studied Jupiter, which is the most massive planet in the solar system, and some of its many moons.Pictures of it sent back by Galileo point to a tortured surface of cracks and jumbled ice. Seeking to understand how such weird topography evolved in a place with such dim sunlight, scientists believe that the answer lies in similar processes on Earth.Their model suggests that Europa's ice shell is about 10 kilometers thick and within it are giant pockets of water, lying at depths as shallow as three kilometers. Warm water from these sub-surface lakes wells up in plumes, causing the ice to become brittle, crack and then collapse. The ice turnover would be a plus for the prospects for life, as it would transfer energy and nutrients between the sub-glacial lake and the surface."One opinion in the scientific community has been if the ice shell is thick, that's bad for biology. That might mean the surface isn't communicating with the underlying ocean," said Britney Schmidt, lead author of the paper and postdoctoral fellow at the Institute for Geophysics, University of Texas at Austin. " Now, we see evidence that it's a thick ice shell that can mix vigorously and new evidence for giant shallow lakes. That could make Europa and its ocean more habitable.""The data opens up some compelling possibilities," said Mary Voytek, director of NASA's Astrobiology Program. "However, scientists worldwide will want to take a close look at this analysis and review the data before we can fully appreciate the implication of these results."

WASHINGTON, Nov. 10 (Xinhua) -- Using its near-infrared vision to peer nine billion years back in time, NASA's Hubble Space Telescope has uncovered an extraordinary population of young dwarf galaxies brimming with star formation, the U.S. space agency announced on Thursday.While dwarf galaxies represent the most common type of galaxy in the universe, the rapid star-birth observed in these newly- found examples may force astronomers to reassess their understanding of the ways in which galaxies form.The galaxies are a hundred times less massive, on average, than the Milky Way, yet they churn out stars at such a furious pace that their stellar content would double in just 10 million years. By comparison, the Milky Way would take a thousand times longer to double its star population.The universe is estimated to be 13.7 billion years old, and these newly-discovered galaxies are extreme even for the young universe -- when most galaxies were forming stars at higher rates than they are today. Astronomers using Hubble's instruments could spot the galaxies because the radiation from young, hot stars has caused the oxygen in the gas surrounding them to light up like a bright neon sign."The galaxies have been there all along, but up until recently astronomers have been able only to survey tiny patches of sky at the sensitivities necessary to detect them," said Arjen van der Wel of the Max Planck Institute for Astronomy in Germany, lead author of a paper on the results to be published online on Nov. 14 in The Astrophysical Journal. "We weren't looking specifically for these galaxies, but they stood out because of their unusual colors. "The observations were part of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS), an ambitious three- year study to analyze the most distant galaxies in the universe. CANDELS is the first census of dwarf galaxies at such an early epoch."In addition to the images, Hubble has captured spectra that show us the oxygen in a handful of galaxies and confirmed their extreme star-forming nature," said co-author Amber Straughn at NASA's Goddard Space Flight Center. "Spectra are like fingerprints. They tell us the galaxies' chemical composition."The CANDELS team uncovered the 69 young dwarf galaxies in near- infrared images taken with Hubble's Wide Field Camera 3 and Advanced Camera for Surveys.The observations suggest that the newly-discovered galaxies were very common nine billion years ago. However, it is a mystery why the newly-found dwarf galaxies were making batches of stars at such a high rate.

WASHINGTON, Jan. 1 (Xinhua) -- Twin U.S. spacecraft to study the moon from crust to core put themselves into the lunar orbit on New Year's Eve and New Year's Day, the country's space agency said.The second Gravity Recovery And Interior Laboratory, or GRAIL-B, reached its lunar orbit at 5:43 p.m. EST (2243 GMT) on Sunday, according to the National Aeronautics and Space Administration (NASA).The GRAIL-A started orbiting the moon at 5 p.m. (2200 GMT) Saturday.The insertion maneuvers placed the spacecraft into a near-polar, elliptical orbit with an orbital period of approximately 11.5 hours, NASA said.Over the coming weeks, the GRAIL team will execute a series of burns with each spacecraft to reduce their orbital period to just under two hours. At the start of the science phase in March 2012, the twin GRAILs will be in a near-polar, near-circular orbit with an altitude of about 55 km."NASA greets the new year with a new mission of exploration," Administrator Charles Bolden said in a statement. "The twin GRAIL spacecraft will vastly expand our knowledge of our moon and the evolution of our own planet."During GRAIL's science mission, the two probes will transmit radio signals precisely defining the distance between them. As they fly over areas of greater and lesser gravity caused by visible features such as mountains, craters and masses hidden beneath the lunar surface, the distance between the twin spacecraft will change slightly.Scientists will translate this information into a high-resolution map of the moon's gravitational field.The data will allow scientists to understand what goes on below the lunar surface and increase knowledge of how Earth and its rocky neighbors in the inner solar system developed into the diverse worlds we see today.