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Twin NASA probes plunge into lunar mountain on purpose

English.news.cn   2012-12-18 06:54:39            

The Photo released by U.S. space agency NASA shows an artist's depiction of Ebb and Flow, the Gravity Recovery and Interior Laboratory (GRAIL) mission probes. Twin NASA spacecraft orbiting the moon ended their mission by crashing into a lunar mountain on purpose Dec. 17, 2012, NASA announced. (Xinhua)

WASHINGTON, Dec. 17 (Xinhua) -- Twin NASA spacecraft orbiting the moon ended their mission by crashing into a lunar mountain on purpose Monday, the U.S. space agency NASA announced.

Ebb and Flow, the Gravity Recovery and Interior Laboratory (GRAIL) mission probes, were sent purposely onto the lunar surface because their low orbit and low fuel levels precluded further scientific operations. This ensures that they don't end up crashing into the Apollo landing sites or any other place on the moon with special importance.

According to NASA, both spacecraft hit the surface at 3,760 mph (1.7 km per second) at around 5:28 p.m. EST (2128 GMT). The mountain where they made contact is located near the moon's north pole. The impact site was in shadow at the time of the crash, so no video of Ebb and Flow's violent demise is expected.

"Impact complete! Ebb and Flow orbiters reach their final destination near the moon's north pole," NASA announced on its tweeter account. "Final resting place on the moon of Ebb and Flow has been named after astronaut and GRAIL collaborator Sally Ride!"

Ride became the first American woman in space as a crew member on space shuttle Challenger in 1983. At the age of 32, she was also the youngest American space traveler at that time.

"Sally was all about getting the job done, whether it be in exploring space, inspiring the next generation, or helping make the GRAIL mission the resounding success it is today," said GRAIL principal investigator Maria Zuber from the Massachusetts Institute of Technology.

"As we complete our lunar mission, we are proud we can honor Sally Ride's contributions by naming this corner of the moon after her."

Fifty minutes prior to the impact, the spacecraft fired their engines until the propellant was depleted. The maneuver was designed to determine precisely the amount of fuel remaining in the tanks. This will help NASA engineers validate computer models to improve predictions of fuel needs for future missions.

The mission team has deduced that much of the material aboard each spacecraft was broken up in the energy released during the impacts. Most of what remained probably is buried in shallow craters. The craters' size may be determined when NASA's Lunar Reconnaissance Orbiter returns images of the area in several weeks.

When launched in September 2011, the probes were named GRAIL A and B. They were renamed Ebb and Flow in January in a nationwide contest. Ebb and Flow were placed in a near-polar, near-circular orbit at an altitude of approximately 34 miles (55 km) on Dec. 31, 2011, and Jan. 1, 2012, respectively.

Since then, the duo spent almost a year mapping the moon's gravity in unprecedented detail. The map will provide a better understanding of how Earth and other rocky planets in the solar system formed and evolved.

"We will miss our lunar twins, but the scientists tell me it will take years to analyze all the great data they got, and that is why we came to the moon in the first place," said GRAIL project manager David Lehman. "So long, Ebb and Flow, and we thank you."

More than 100 missions have been flung to Earth's nearest neighbor since the dawn of the Space Age. Included were NASA's six Apollo moon landings that put 12 astronauts on the surface.

The demise of Ebb and Flow comes in the same month as the 40th launch anniversary of Apollo 17, the last manned mission to the moon. The last time NASA intentionally fired manmade objects at the moon was in 2009.

Editor: znz
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