Here is a picture of the impact mark that the object the struck Jupiter on July 19th left. This picture was taken on July 23rd by the Hubble telescope. What I find interesting is that no one noticed it until after the object struck Jupiter. Even then, it was an amateur astronomer in Australia, Anthony Wesley, who first noticed it and notified the professional astronomers that something had happened.
From what I read the object was described as the size of several football fields, which means that the object was probably a few hundred meter across. They also mentioned that the force of the impact was thousands of times more powerful than the Tunguska event of 1908. Since the Tunguska event is usually estimated as 10 to 15 megatons and it knocked down trees over 830 square miles, that is a pretty serious hit.
The various places I've read describe the mark as twice the length of the United States or nearly as big as the Pacific Ocean. Now if an object of this size struck the Earth, it probably wouldn't hit nearly as hard, since the escape velocity of Jupiter is 5.3 times as high as the Earth's escape velocity. Some comets are moving much faster than Jupiter escape velocity to begin with, so it could hit nearly as hard.
What is interesting, is that when an meteorite explodes before it gets to the ground it may actually do more damage than one the hit the ground. The Tunguska object exploded 4-6 miles above the Earth and the damage was similar to that caused by an air burst of a thermonuclear bomb. It turns out there are meteorite explosions in the 20 kiloton range happen every year, but too far up to cause damage. Some estimates put the Tunguska object as about 60 meters across.
Based on what I have read, you would need something at least 30 or 40 meters across to do serious damage and that would depend on exact trajectory, velocity and composition of the object and of course if the impact point was inhabited. Also, even if we had significant warning, I suspect that we could not pinpoint the impact point very closely. We are talking about the the impact point predictions that might cover a 100,000 square miles. This makes the usual hurricane evacuation scenario look tame by comparison. We can only hope that the next time is over the ocean or in a sparsely inhabited area.
Links:
Addition: July 29, 2009:
Jonah Goldberg has column in the LA Times on the same subject:
http://www.latimes.com/news/opinion/la-oe-goldberg28-2009jul28,0,3694237.column
Hubblesite:
http://hubblesite.org/newscenter/archive/releases/2009/23/image/a/
Wikipedia-Tunguska Event
http://en.wikipedia.org/wiki/Tunguska_event
Original Report from Anthony Wesley
http://jupiter.samba.org/jupiter-impact.html
NY Times Infrared Picture
http://www.nytimes.com/2009/07/22/science/space/22jupiter.html
From what I read the object was described as the size of several football fields, which means that the object was probably a few hundred meter across. They also mentioned that the force of the impact was thousands of times more powerful than the Tunguska event of 1908. Since the Tunguska event is usually estimated as 10 to 15 megatons and it knocked down trees over 830 square miles, that is a pretty serious hit.
The various places I've read describe the mark as twice the length of the United States or nearly as big as the Pacific Ocean. Now if an object of this size struck the Earth, it probably wouldn't hit nearly as hard, since the escape velocity of Jupiter is 5.3 times as high as the Earth's escape velocity. Some comets are moving much faster than Jupiter escape velocity to begin with, so it could hit nearly as hard.
What is interesting, is that when an meteorite explodes before it gets to the ground it may actually do more damage than one the hit the ground. The Tunguska object exploded 4-6 miles above the Earth and the damage was similar to that caused by an air burst of a thermonuclear bomb. It turns out there are meteorite explosions in the 20 kiloton range happen every year, but too far up to cause damage. Some estimates put the Tunguska object as about 60 meters across.
Based on what I have read, you would need something at least 30 or 40 meters across to do serious damage and that would depend on exact trajectory, velocity and composition of the object and of course if the impact point was inhabited. Also, even if we had significant warning, I suspect that we could not pinpoint the impact point very closely. We are talking about the the impact point predictions that might cover a 100,000 square miles. This makes the usual hurricane evacuation scenario look tame by comparison. We can only hope that the next time is over the ocean or in a sparsely inhabited area.
Links:
Addition: July 29, 2009:
Jonah Goldberg has column in the LA Times on the same subject:
http://www.latimes.com/news/opinion/la-oe-goldberg28-2009jul28,0,3694237.column
Hubblesite:
http://hubblesite.org/newscenter/archive/releases/2009/23/image/a/
Wikipedia-Tunguska Event
http://en.wikipedia.org/wiki/Tunguska_event
Original Report from Anthony Wesley
http://jupiter.samba.org/jupiter-impact.html
NY Times Infrared Picture
http://www.nytimes.com/2009/07/22/science/space/22jupiter.html
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