正文
Step by Step 3000 第3册 Unit4:News reports(2)
B. Keywords.
robotic rover, robotic arm, atmosphere, sub-surface.
Vocabulary.
installment, retrorocket, descent, condensate, finale, tentatively,
Polar Lander, Mars Climate Orbiter, Mars Global Surveyor Orbiter.
Now listen to the second news report, then summarize the news according to the cues given.
Of all the US and Russian spacecrafts that have travelled to the Mars since the 1960s, the Polar Lander is to be the first to touch down near the planet's south pole.
The Lander and a companion orbiting craft called the Mars Climate Orbiter launched in December, are the second installment of a 12 year of NASA program began in 1996, to unlock the secrets over earth's red neighbor.
The first installment, the Mars Global Surveyor Orbiter and the Pathfinder Lander, arrived in 1997, with Pathfinder's robotic rover collecting and analyzing rocks on a desert about half a world away from the polar landing site.
The Landers is to touch down just above the northern-most edge of the south polar ice cap, believed to be a mixture of water and carbon dioxide.
It will use retrorockets to slow its descent.
Once on the ground, it will employ a robotic arm resembling a child's toy construction shovel to dig in search for subsurface water.
Together with the newest orbiter now on its way to Mars, the Lander will also measure the distribution of water vapor, dust and condensates in the Martian atmosphere.
While the Polar Lander descends next December, it is to release two speeding probes, each smaller than a basketball.
These rugged instruments are to crash at about 640 kilometers per hour and bury themselves into the Martian surface about 100 kilometers away from the Lander's touch-down point.
They, too, will be inspecting for subsurface water.
The grand finale of this series of Mars probes is tentatively set for launching in 2005.
It will return soil and rock samples to earth three years later.
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