综合一区欧美国产,99国产麻豆免费精品,九九精品黄色录像,亚洲激情青青草,久久亚洲熟妇熟,中文字幕av在线播放,国产一区二区卡,九九久久国产精品,久久精品视频免费

World / US and Canada

NASA is back at Mars

(Agencies) Updated: 2014-09-22 11:10

NASA is back at Mars
[Infographic/Agencies]

CAPE CANAVERAL, Fla - A NASA robotic spacecraft fired its braking rockets on Sunday, ending a 10-month journey to put itself into orbit around Mars and begin a hunt for the planet's lost water.

After traveling 442 million miles (71 million km), the Mars Atmosphere and Volatile Evolution, or MAVEN, spacecraft fired its six rocket thrusters, trimming its speed from 12,800 mph (20,600 kph) to 10,000 mph (16,093 kph).

The 33-minute engine firing left MAVEN in the clutches of Mars' gravity as it flew over the planet's north pole and slipped into a looping 236-mile by 27,713-mile (380-km by 44,600-km) high orbit.

"I don't have any fingernails anymore, but we made it," Colleen Hartman, NASA deputy director for science at Goddard Space Spaceflight Center in Greenbelt, Md., said during a NASA Television broadcast of MAVEN's arrival.

Flight control teams burst into cheers and applause as radio signals from MAVEN confirmed it was in Mars orbit at 10:25 p.m. EDT/0225 GMT.

Over the next several weeks, MAVEN will lower its altitude until it reaches its 93-mile by 3,900-mile (150-km by 6,200-km) operational orbit.

MAVEN will study how the solar wind strips away atoms and molecules in the planet's upper atmosphere, a process that scientists believe has been underway for eons.

"By learning the processes that are going on today we hope to extrapolate back and learn about the history of Mars," MAVEN scientist John Clarke, with Boston University, said in an interview on NASA Television.

Scientists strongly suspect that Mars was not always the cold and dry desert it is today. The planet's surface is riddled with what appear to be dry riverbeds and minerals that form in the presence of water.

But for water to pool on the planet's surface, its atmosphere would have had to be much denser and thicker than it is today. Mars' atmosphere is now about 100 times thinner than Earth's.

Scientists suspect Mars lost 99 percent of its atmosphere over millions of years as the planet cooled and its magnetic field decayed, allowing charged particles in the solar wind to strip away water and other atmospheric gases.

Learning about how Mars lost its water is key to understanding if the planet most like Earth in the solar system ever could have supported life.

The $671-million MAVEN mission is scheduled to last one year. The spacecraft joins two other NASA orbiters, two NASA rovers and a European orbiter currently working at Mars.

A seventh Mars probe owned by India is scheduled to arrive on Wednesday.

 

Trudeau visits Sina Weibo
May gets little gasp as EU extends deadline for sufficient progress in Brexit talks
Ethiopian FM urges strengthened Ethiopia-China ties
Yemen's ex-president Saleh, relatives killed by Houthis
Most Popular
Hot Topics

...
甘肃省| 朝阳区| 鄂尔多斯市| 北辰区| 宜君县| 濮阳县| 茂名市| 顺平县| 泰州市| 苍南县| 普兰店市| 尚志市| 大关县| 古丈县| 大悟县| 汽车| 凤翔县| 筠连县| 沁源县| 广德县| 华池县| 广灵县| 营山县| 永昌县| 安宁市| 开远市| 江油市| 宾川县| 上饶县| 邛崃市| 旬邑县| 罗甸县| 松阳县| 金坛市| 龙游县| 德阳市| 新蔡县| 合阳县| 建昌县| 莱西市| 莎车县|