week four--Mars

Rover Curiosity lands safely on Mars

By Elizabeth Landau, CNN

Updated 0516 GMT (1316 HKT) August 6, 2012

  NASA's $2.5 billion rover, Curiosity, will make its dramatic entrance into Martian territory in a spectacle popularly known as the "seven minutes of terror." This jaw-dropping landing process, involving a sky crane and the world's largest supersonic parachute, allows the spacecraft carrying Curiosity to target the landing area that scientists have meticulously chosen.

  The spacecraft is "healthy and right on course," according to the latest update from NASA. Curiosity has been traveling away from Earth since November 26.

  In these layers, scientists are looking for organic molecules, which are necessary to create life. But even if Curiosity finds them, that's not proof that life existed -- after all, these molecules are found in bus exhaust and meteorites, too, says Steve Squyres, part of the Mars Science Laboratory science team.

  If there aren't any organics, that may suggest there's something on the planet destroying these molecules, says James Wray, assistant professor of Earth and atmospheric sciences at the Georgia Institute of Technology and collaborator on the Curiosity science team. But if Curiosity detects them, Wray said, that might help scientists move from asking, "Was Mars ever habitable?" to "Did Mars actually host life?"

  "A successful landing will grant a huge breath of relief to the entire Mars science community tonight," Wray said in an e-mail. "And it will certainly keep NASA at the forefront of Mars exploration for at least the next few years."

  Liquid water is not something scientists expect to be apparent on Mars because the planet is so cold and dry, Squyres said. If the planet does harbor liquid water today, it would have to be deep below the surface, perhaps peeking out in a few special places, but not likely to be seen by Curiosity, Squyres said.

  It's hard to know how long ago liquid water would have been there because there's no mechanism to date the rocks that rovers find on Mars, Squyres said.

  Evidence from the spacecraft NASA has sent to Mars so far suggests that the "warm and wet" period on Mars lasted for the first billion years of the planet's history.

  "In order to create life, you need both the right environmental conditions -- which includes liquid water -- and you need the building blocks from which life is built, which includes organics," Squyres said. The Mars Science Laboratory is a precursor mission to sharper technology that could do life detection, Grotzinger said.

  There aren't specific molecules that scientists are looking for with Curiosity. The attitude is: "Let's go to an interesting place with good tools and find out what's there," Squyres said.

  Curiosity is supposed to last for two years on Mars, but it may operate longer -- after all, Spirit and Opportunity, which arrived on Mars in 2004, were each only supposed to last 90 Martian days. Spirit stopped communicating with NASA in 2010 after getting stuck in sand, and Opportunity is still going.

網址:http://edition.cnn.com/2012/08/05/tech/mars-rover-curiosity/

Structure of the Lead：

who:Curiosity

when:August,6,2012

what:Curiosity has been traveling away from Earth since November 26

why:scientists are looking for orgsnic molecules,which are necessary to create life   

where:Mars

how:in order to create lige, you need both the right environmental conditions--which includes liquid water--and you need the building blocks from which life is built,which includes organic  

keywords:

Curiosity:好奇號

Mars:火星

organic molecules:有機分子

liquid water:液態水

cold and dry:冷又乾