译文:小行星可能撞击火星

原文:Asteroid May Hit Mars

   科学家星期三宣称有大块太空岩石以1/75的机率撞击火星。

    史蒂文切斯利，美国宇航局喷射推进实验室近地球目标计划的科学家说：“这种机率极不寻常。当我们跟踪......威胁小行星的物体时经常选取那些可能性较大的物体进行研究”。

这颗小行星在2007年数据研究中比较有名，在11月份下旬被发现，它的尺寸与1908年撞击遥远的西伯利亚中心的那颗不明物很相似。

     这颗小行星所发出的能量相当于是15兆吨原子弹爆炸的威力，可以扫除6千万棵树。

科学家们追踪的这颗小行星，位于地球和火星正中问，起初撞击的可能性只有1/350，但本周已经上升了这种机率。

A newly discovered hunk of space rock has a 1 in 75 chance of slamming into the Red Planet on Jan. 30, scientists said Thursday.

"These odds are extremely unusual. We frequently work with really long odds when we track ... threatening asteroids," said Steve Chesley, an astronomer with the Near Earth Object Program at NASA's Jet Propulsion Laboratory.

The asteroid, known as 2007 WD5, was discovered in late November and is similar in size to an object that hit remote central Siberia in 1908.

The asteroid is unleashing energy equivalent to a 15-megaton nuclear bomb and wiping out 60 million trees.

Scientists tracking the asteroid, currently halfway between Earth and Mars, initially put the odds of impact at 1 in 350 but increased the chances this week.

Scientists expect the odds to diminish again early next month after getting new observations of the asteroid's orbit, Chesley said.

"We know that it's going to fly by Mars and most likely going to miss, but there's a possibility of an impact," he said.

If the asteroid does smash into Mars, it will probably hit near the equator close to where the rover Opportunity has been exploring the Martian plains since 2004.

The robot is not in danger because it lies outside the impact zone.

Speeding at 8 miles a second, a collision would carve a hole the size of the famed Meteor Crater in Arizona.

In 1994, fragments of the comet Shoemaker-Levy 9 smacked into Jupiter, creating a series of overlapping fireballs in space.

Astronomers have yet to witness an asteroid impact with another planet.

"Unlike an Earth impact, we're not afraid, but we're excited," Chesley said.