Leonard David
26 January 2012
Full Article:
http://www.space.com/14370-asteroid-shield-earth-threat-protection-meeting.html
They can be mean and nasty, and they can mess up our planet big time.
They are near-Earth objects, dubbed NEOs, celestial flotsam such as asteroids or comets that can, and have, scored direct hits on our humble home planet.
A new international consortium has been launched to address the impact threat to Earth, but, more pointedly, to organize, prepare and implement mitigation measures.
Called NEOShield, the European Commission is providing a significant amount of euros to support the initiative. The undertaking consists of research institutes, universities and industrial partners in Germany, France, the United Kingdom and Spain, as well as in the U.S. and Russia.
The primary aim of NEOShield is to investigate in detail the three most promising asteroid threat-reduction techniques: kinetic impactors, gravity tractors, and the explosive blast-deflection method.
That's the crux of the undertaking as spelled out by Alan Harris, a senior scientist and NEOShield project leader at the German Aerospace Center's Institute of Planetary Research in Berlin-Adlershof, Germany.
The DLR is the coordinating partner for the multiyear NEOShield project and is set to roll out the plan this week.
"The scientific side of this will include the analysis of observational data on NEOs and laboratory experiments in which projectiles are fired at asteroid surface analog materials with different compositions, densities, porosities and structures," Harris told SPACE.com. "We need to understand how the momentum transfer from a kinetic impactor to an asteroid depends on the physical characteristics of the asteroid."
In this week's meeting, specialists from Europe, for example, will draw upon their past kinetic impactor work on the European Space Agency's study of a mission tagged as Don Quijote — an idea for an asteroid-deflection precursor mission drawn up several years ago.
NEOShield work will employ sophisticated computer modeling and simulations. Those will enable researchers to scale up knowledge and apply that information to a real-case scenario that calls for a spacecraft-deployed impactor slamming into a real asteroid in space...
Showing posts with label Comet. Show all posts
Showing posts with label Comet. Show all posts
Wednesday, February 29, 2012
Saturday, November 5, 2011
Comet May Have Missed Earth by a Few Hundred Kilometers in 1883
Billion-Ton Comet May Have Missed Earth by a Few Hundred Kilometers in 1883
A reanalysis of historical observations suggest Earth narrowly avoided an extinction event just over a hundred years ago.
10/17/2011
http://www.technologyreview.com/blog/arxiv/27264
On 12th and 13th August 1883, an astronomer at a small observatory in Zacatecas in Mexico made an extraordinary observation. José Bonilla counted some 450 objects, each surrounded by a kind of mist, passing across the face of the Sun.
Bonilla published his account of this event in a French journal called L'Astronomie in 1886. Unable to account for the phenomenon, the editor of the journal suggested, rather incredulously, that it must have been caused by birds, insects or dust passing front of the Bonilla's telescope. (Since then, others have adopted Bonilla's observations as the first evidence of UFOs.)
Today, Hector Manterola at the National Autonomous University of Mexico in Mexico City, and a couple of pals, give a different interpretation. They think that Bonilla must have been seeing fragments of a comet that had recently broken up. This explains the 'misty' appearance of the pieces and why they were so close together.
But there's much more that Manterola and co have deduced. They point out that nobody else on the planet seems to have seen this comet passing in front of the Sun, even though the nearest observatories in those days were just a few hundred kilometers away.
That can be explained using parallax. If the fragments were close to Earth, parallax would have ensured that they would not have been in line with the Sun even for observers nearby. And since Mexico is at the same latitude as the Sahara, northern India and south-east Asia, it's not hard to imagine that nobody else was looking.
Manterola and pals have used this to place limits on how close the fragments must have been: between 600 km and 8000 km of Earth. That's just a hair's breadth.
What's more, Manterola and co estimate that these objects must have ranged in size from 50 to 800 metres across and that the parent comet must originally have tipped the scales at a billion tons or more, that's huge, approaching the size of Halley's comet.
That's an eye opening reexamination of the data. Astronomers have seen a number of other comets fragment. The image above shows the Schwassmann-Wachmann 3 comet which broke apart as it reentered the inner Solar System in 2006. There's no reason why such fragments couldn't pass close by Earth.
One puzzle is why nobody else saw this comet. It must have been particularly dull to have escaped observation before and after its close approach. However, Manterola and co suggest that it may have been a comet called Pons-Brooks seen that same year by American astronomers.
Manterola and co end their paper by spelling out just how close Earth may have come to catastrophe that day. They point out that Bonilla observed these objects for about three and a half hours over two days. This implies an average of 131 objects per hour and a total of 3275 objects in the time between observations.
Each fragment was at least as big as the one thought to have hit Tunguska. Manterola and co end with this: "So if they had collided with Earth we would have had 3275 Tunguska events in two days, probably an extinction event."
A sobering thought.
A reanalysis of historical observations suggest Earth narrowly avoided an extinction event just over a hundred years ago.
10/17/2011
http://www.technologyreview.com/blog/arxiv/27264
On 12th and 13th August 1883, an astronomer at a small observatory in Zacatecas in Mexico made an extraordinary observation. José Bonilla counted some 450 objects, each surrounded by a kind of mist, passing across the face of the Sun.
Bonilla published his account of this event in a French journal called L'Astronomie in 1886. Unable to account for the phenomenon, the editor of the journal suggested, rather incredulously, that it must have been caused by birds, insects or dust passing front of the Bonilla's telescope. (Since then, others have adopted Bonilla's observations as the first evidence of UFOs.)
Today, Hector Manterola at the National Autonomous University of Mexico in Mexico City, and a couple of pals, give a different interpretation. They think that Bonilla must have been seeing fragments of a comet that had recently broken up. This explains the 'misty' appearance of the pieces and why they were so close together.
But there's much more that Manterola and co have deduced. They point out that nobody else on the planet seems to have seen this comet passing in front of the Sun, even though the nearest observatories in those days were just a few hundred kilometers away.
That can be explained using parallax. If the fragments were close to Earth, parallax would have ensured that they would not have been in line with the Sun even for observers nearby. And since Mexico is at the same latitude as the Sahara, northern India and south-east Asia, it's not hard to imagine that nobody else was looking.
Manterola and pals have used this to place limits on how close the fragments must have been: between 600 km and 8000 km of Earth. That's just a hair's breadth.
What's more, Manterola and co estimate that these objects must have ranged in size from 50 to 800 metres across and that the parent comet must originally have tipped the scales at a billion tons or more, that's huge, approaching the size of Halley's comet.
That's an eye opening reexamination of the data. Astronomers have seen a number of other comets fragment. The image above shows the Schwassmann-Wachmann 3 comet which broke apart as it reentered the inner Solar System in 2006. There's no reason why such fragments couldn't pass close by Earth.
One puzzle is why nobody else saw this comet. It must have been particularly dull to have escaped observation before and after its close approach. However, Manterola and co suggest that it may have been a comet called Pons-Brooks seen that same year by American astronomers.
Manterola and co end their paper by spelling out just how close Earth may have come to catastrophe that day. They point out that Bonilla observed these objects for about three and a half hours over two days. This implies an average of 131 objects per hour and a total of 3275 objects in the time between observations.
Each fragment was at least as big as the one thought to have hit Tunguska. Manterola and co end with this: "So if they had collided with Earth we would have had 3275 Tunguska events in two days, probably an extinction event."
A sobering thought.
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