Post by Dominico Baggio on Apr 17, 2005 12:41:13 GMT
Asteroid 'May Yet Pose Threat'
Scientists fear the Earth's gravity might shift the asteroid on to a collision course
An huge asteroid that caused a brief scare over its possible collision with Earth may yet pose a threat.
Scientists were shocked when they calculated there was a one in 38 chance of the 1,000ft-wide space rock hitting the Earth on Friday April 13, 2029.
They breathed a sigh of relief when further observations showed that the date was not so unlucky after all.
The asteroid, big enough to flatten Texas and listed as 2004 MN4, will miss the Earth by the slim but safe margin of about 25,000 miles - roughly a quarter of the distance to the Moon.
But it could be too soon to write off the danger. Experts are now warning that the near approach in 2029 might upset the asteroid's orbit, sending it on a potential collision course sometime later.
More on 2004 MN4
AOL Learning
2004 MN4 Near-Earth Asteroid
Nasa Earth Impact Risk Summary
Have your say on the message board
Even a tiny change in trajectory caused by the Earth's gravity could theoretically lead to an impact in 2034 or 2035, or another date in the future. The unpredictability of the asteroid's behaviour after 2029 means the danger might not become apparent until it is too late.
As a safety precaution, some experts are now calling for 2004 MN4 to be "tagged'' with a transponder that would constantly radio its position. Scientists hope this will provide sufficient warning to allow emergency action if necessary, possibly by diverting the object away from the Earth.
Other instruments on the probe could also provide valuable information about the asteroid's composition.
Anthropologist Dr Benny Peiser, from Liverpool John Moore's University, an expert on asteroid hazards, said: "In 2029 the asteroid won't hit us, but it will come very close. The interesting thing is we haven't got a clue what's going to happen after that.
"We don't know what that asteroid is made of, and that might influence the way it's affected by the Earth's gravitational pull.
"There are other close approaches in 2034 and 2035. Given that we don't know exactly how the orbit will change, there's a minute chance that it will turn into something much more problematical.
"In all likelihood it will produce an orbit that will not intercept the Earth, but we don't know, and that's the problem.''
Although 2004 MN4 is not of a size to threaten the human race, the effect of an impact would be devastating.
The asteroid is defined as a "regional hazard'' - big enough to flatten Texas or a large chunk of Europe with an explosive force equivalent to 10,000 megatons of dynamite. That is more than the combined power of all the nuclear weapons in the world.
Dr Peiser said an opportunity to plant a transponder on the asteroid would come in 2012. The object would then be 10 million miles from Earth.
"That's not a big distance as far as space missions go,'' he said.
"I'm in favour of the idea. From a psychological point of view, it would enormously reassure people that we can tackle such complex problems.
"This is most likely not the object with our number on it, but one day we will have to address this question and we'll need the technology. A transponder mission shouldn't be too complicated or costly, and would provide a lot of vital data.''
Scientists fear the Earth's gravity might shift the asteroid on to a collision course
An huge asteroid that caused a brief scare over its possible collision with Earth may yet pose a threat.
Scientists were shocked when they calculated there was a one in 38 chance of the 1,000ft-wide space rock hitting the Earth on Friday April 13, 2029.
They breathed a sigh of relief when further observations showed that the date was not so unlucky after all.
The asteroid, big enough to flatten Texas and listed as 2004 MN4, will miss the Earth by the slim but safe margin of about 25,000 miles - roughly a quarter of the distance to the Moon.
But it could be too soon to write off the danger. Experts are now warning that the near approach in 2029 might upset the asteroid's orbit, sending it on a potential collision course sometime later.
More on 2004 MN4
AOL Learning
2004 MN4 Near-Earth Asteroid
Nasa Earth Impact Risk Summary
Have your say on the message board
Even a tiny change in trajectory caused by the Earth's gravity could theoretically lead to an impact in 2034 or 2035, or another date in the future. The unpredictability of the asteroid's behaviour after 2029 means the danger might not become apparent until it is too late.
As a safety precaution, some experts are now calling for 2004 MN4 to be "tagged'' with a transponder that would constantly radio its position. Scientists hope this will provide sufficient warning to allow emergency action if necessary, possibly by diverting the object away from the Earth.
Other instruments on the probe could also provide valuable information about the asteroid's composition.
Anthropologist Dr Benny Peiser, from Liverpool John Moore's University, an expert on asteroid hazards, said: "In 2029 the asteroid won't hit us, but it will come very close. The interesting thing is we haven't got a clue what's going to happen after that.
"We don't know what that asteroid is made of, and that might influence the way it's affected by the Earth's gravitational pull.
"There are other close approaches in 2034 and 2035. Given that we don't know exactly how the orbit will change, there's a minute chance that it will turn into something much more problematical.
"In all likelihood it will produce an orbit that will not intercept the Earth, but we don't know, and that's the problem.''
Although 2004 MN4 is not of a size to threaten the human race, the effect of an impact would be devastating.
The asteroid is defined as a "regional hazard'' - big enough to flatten Texas or a large chunk of Europe with an explosive force equivalent to 10,000 megatons of dynamite. That is more than the combined power of all the nuclear weapons in the world.
Dr Peiser said an opportunity to plant a transponder on the asteroid would come in 2012. The object would then be 10 million miles from Earth.
"That's not a big distance as far as space missions go,'' he said.
"I'm in favour of the idea. From a psychological point of view, it would enormously reassure people that we can tackle such complex problems.
"This is most likely not the object with our number on it, but one day we will have to address this question and we'll need the technology. A transponder mission shouldn't be too complicated or costly, and would provide a lot of vital data.''
(I studied physics at university)
