Post by Andrei Tchentchik on Jun 26, 2019 18:24:58 GMT 2
(.#224).- The White House takes the threat of asteroids very seriously.
The White House takes the threat of asteroids very seriously.
By Tristan Vey - Published 28/06/2018 at 18:45
Artist's impression of an asteroid fall on Earth. 51266672 / James Thew - stock.adobe.com
Last week, the US presidency released an inter-agency report outlining a plan of action to better take into account and anticipate the danger posed by the fall of an asteroid for humanity.
This may come as a surprise, but an asteroid tens of meters in diameter would be enough to scratch a city like Paris on the map. But millions of objects of this size cross the orbit of the Earth, according to astronomers (we call them "NEOs"). And we do not know more than 10% ... The vast majority walks in the immensity of space vacuum without knowing when they could crash on the surface of the Earth. The probability is fortunately very small, but it is not zero: on average, it falls an object of about twenty meters per century. The White House last week released its first action plan outlining the strategy it would adopt to manage this meteorite threat.
At the beginning of the 20th century, a car of this type fell in Siberia, destroying everything within a radius of 20 km and setting millions of trees within a radius of 100 km. This is called the Tunguska event. It has released energy estimated between 5 and 10 million tons of TNT, hundreds of times more than the first atomic bombs. If such an object had crashed on New York, it would have killed millions of people, warns in preamble the inter-agency report released by the White House last week.
What to do then to avoid such a drama? "The advantage over other natural disasters that will always remain more or less unpredictable is that we could predict the occurrence of this type of event," said Patrick Michel, specialist asteroids at the Observatory of the Côte d 'Azure. "Provided you make some investments, of course. But for a few billion euros only, we could know all the objects over 140 meters that threaten us several years in advance and prepare demonstration missions of different diversion technologies. "
Far from detection objects set by the Congress
The figure of 140 meters corresponds to a relatively arbitrary limit above which an asteroid is thought to have an impact on the human being, no matter where on Earth it crashes. The US Congress set a goal in 2005 of identifying, by 2020, 90% of the 25,000 objects whose size would exceed this threshold. This goal will not be achieved, stresses the new report. Pan-STARRS systematic observation programs and Catalina Sky Survey were not enough. Today only one third of these objects are known. The future LSST, which will come into service in 2023, will increase the number of detections, but it will not achieve this goal before long. But we should also identify objects over 50 meters, today recommends the action plan of the White House. It remains to be seen how. "It is not technically impossible, but it would cost much more," warns Patrick Michel. "I do not think countries are ready for such investments. The risk of such an object falling on an inhabited area remains very low. "
The European Space Agency's (ESA) FlyEye telescope, currently under construction in Sicily, will make it possible to flush out objects of this type, but only a few weeks before they hit the Earth. Just enough to prepare evacuations. Provided the trajectory models are accurate enough to identify the impact area with certainty. The report calls for investment in this type of modeling and stresses the need to prepare the authorities for this eventuality. "This is one of the main thrusts of the report," said Daniel Hestroffer, astronomer at the Paris Observatory who works on these issues of protection of the Earth. "In Europe, a few exercises were set up by ESA, in 2014 and again in 2015, involving space agencies and safety organizations from a few member countries, but that's about it. There has been nothing at the national level. "The UN itself takes these issues very seriously. Two working groups have been set up, partly to identify the specialists and institutions to be put in touch in the event of a threat.
How to deflect asteroids?
But what to do concretely if a 200-meter asteroid threatened to crash on Earth in five years for example? An American mission, DART, is due to fly in December 2020 to test a kinetic impact deflection technology in 2022 on a pair of asteroids. In short, this amounts to launching a very strong metallic missile to try to deviate (very slightly) the asteroid from its trajectory early enough so that it can avoid the Earth.
Europe, which was to send a probe to complete the mission and study finely in situ the deviation induced by the impactor, gave up financing the project whose cost did not exceed 250 million euros ... A mission replacement, Hera, more economical, was set up. ESA must decide at the end of 2019 to fund it or not. Given the delays, it will not be able to arrive there until 2026. "This is sufficient to accomplish the main initial objectives of characterization of the target, impact crater and measurement of the deviation," says Patrick Michel. "It will also help maintain ESA-NASA international cooperation in an area where it is a major issue." Although it would obviously have been better to arrive on the spot at the same time as the Americans, in 2022 ...
The second solution would be to send a "gravitational tractor". The idea is this time to send a probe that will exert a very fine attraction on the asteroid, but long enough to change its trajectory. This would, however, require anticipating the impact with the Earth a very long time in advance. Which brings us back to the problem of detection. Which is far from resolved. Meanwhile, the next asteroid that could cause major damage to Earth may already be on its way ...
F I N .
The White House takes the threat of asteroids very seriously.
By Tristan Vey - Published 28/06/2018 at 18:45
Artist's impression of an asteroid fall on Earth. 51266672 / James Thew - stock.adobe.com
Last week, the US presidency released an inter-agency report outlining a plan of action to better take into account and anticipate the danger posed by the fall of an asteroid for humanity.
This may come as a surprise, but an asteroid tens of meters in diameter would be enough to scratch a city like Paris on the map. But millions of objects of this size cross the orbit of the Earth, according to astronomers (we call them "NEOs"). And we do not know more than 10% ... The vast majority walks in the immensity of space vacuum without knowing when they could crash on the surface of the Earth. The probability is fortunately very small, but it is not zero: on average, it falls an object of about twenty meters per century. The White House last week released its first action plan outlining the strategy it would adopt to manage this meteorite threat.
At the beginning of the 20th century, a car of this type fell in Siberia, destroying everything within a radius of 20 km and setting millions of trees within a radius of 100 km. This is called the Tunguska event. It has released energy estimated between 5 and 10 million tons of TNT, hundreds of times more than the first atomic bombs. If such an object had crashed on New York, it would have killed millions of people, warns in preamble the inter-agency report released by the White House last week.
What to do then to avoid such a drama? "The advantage over other natural disasters that will always remain more or less unpredictable is that we could predict the occurrence of this type of event," said Patrick Michel, specialist asteroids at the Observatory of the Côte d 'Azure. "Provided you make some investments, of course. But for a few billion euros only, we could know all the objects over 140 meters that threaten us several years in advance and prepare demonstration missions of different diversion technologies. "
Far from detection objects set by the Congress
The figure of 140 meters corresponds to a relatively arbitrary limit above which an asteroid is thought to have an impact on the human being, no matter where on Earth it crashes. The US Congress set a goal in 2005 of identifying, by 2020, 90% of the 25,000 objects whose size would exceed this threshold. This goal will not be achieved, stresses the new report. Pan-STARRS systematic observation programs and Catalina Sky Survey were not enough. Today only one third of these objects are known. The future LSST, which will come into service in 2023, will increase the number of detections, but it will not achieve this goal before long. But we should also identify objects over 50 meters, today recommends the action plan of the White House. It remains to be seen how. "It is not technically impossible, but it would cost much more," warns Patrick Michel. "I do not think countries are ready for such investments. The risk of such an object falling on an inhabited area remains very low. "
The European Space Agency's (ESA) FlyEye telescope, currently under construction in Sicily, will make it possible to flush out objects of this type, but only a few weeks before they hit the Earth. Just enough to prepare evacuations. Provided the trajectory models are accurate enough to identify the impact area with certainty. The report calls for investment in this type of modeling and stresses the need to prepare the authorities for this eventuality. "This is one of the main thrusts of the report," said Daniel Hestroffer, astronomer at the Paris Observatory who works on these issues of protection of the Earth. "In Europe, a few exercises were set up by ESA, in 2014 and again in 2015, involving space agencies and safety organizations from a few member countries, but that's about it. There has been nothing at the national level. "The UN itself takes these issues very seriously. Two working groups have been set up, partly to identify the specialists and institutions to be put in touch in the event of a threat.
How to deflect asteroids?
But what to do concretely if a 200-meter asteroid threatened to crash on Earth in five years for example? An American mission, DART, is due to fly in December 2020 to test a kinetic impact deflection technology in 2022 on a pair of asteroids. In short, this amounts to launching a very strong metallic missile to try to deviate (very slightly) the asteroid from its trajectory early enough so that it can avoid the Earth.
Europe, which was to send a probe to complete the mission and study finely in situ the deviation induced by the impactor, gave up financing the project whose cost did not exceed 250 million euros ... A mission replacement, Hera, more economical, was set up. ESA must decide at the end of 2019 to fund it or not. Given the delays, it will not be able to arrive there until 2026. "This is sufficient to accomplish the main initial objectives of characterization of the target, impact crater and measurement of the deviation," says Patrick Michel. "It will also help maintain ESA-NASA international cooperation in an area where it is a major issue." Although it would obviously have been better to arrive on the spot at the same time as the Americans, in 2022 ...
The second solution would be to send a "gravitational tractor". The idea is this time to send a probe that will exert a very fine attraction on the asteroid, but long enough to change its trajectory. This would, however, require anticipating the impact with the Earth a very long time in advance. Which brings us back to the problem of detection. Which is far from resolved. Meanwhile, the next asteroid that could cause major damage to Earth may already be on its way ...
F I N .
