Why astronomers didn't detect Russian meteor before it hit Earth on February 15
Washington: We didn't receive any warning about the Russian meteor before it hit the Earth because small asteroids are very difficult to spot with telescopes as they only reflect a little sunlight, according to a scientist from the University of Southampton.
Dr. Hugh Lewis, a lecturer in aerospace engineering at Southampton University, has analyzed the extraordinary event using the "NEOImpactor" tool, which was developed by researchers from the university and designed to investigate the risks faced by the Earth from asteroid impacts.
On the morning of Friday 15 February, an asteroid estimated to be the size of a five-story building entered the atmosphere over the Urals region of Russia and disintegrated. It generated a blast wave that blew out windows and damaged buildings in the city of Chelyabinsk, injuring more than 1,000 people.
Just a few hours later, the world witnessed the 40-meter asteroid 2012 DA14 pass between the Earth and the ring of geostationary satellites ; the closest approach of an object this size for a century.
Explaining the significance of the event, Dr. Hugh Lewis: "This is the first time that we've seen injuries resulting from a collision between the Earth and an asteroid. I think that what surprised most people was the scale of the damage from a relatively small object and the fact that we didn't have any warning."
In fact, the asteroid's size explains the lack of warning, he said.
Scientists have suggested that the energy released in the blast was equivalent to 500 kilotons of TNT.
Using the NEOImpactor tool and estimates of the size, speed and path, Dr. Lewis simulated the flight of the meteor up to the point where it disintegrated above Chelyabinsk. NEOImpactor then provided an estimate of the number of people affected by the shockwave and the cost of damage to the buildings in the region.
"The results show that a few thousand people in the Chelyabinsk region could have been affected by the blast wave with damage to the surrounding area costing about 100 million dollars, which fits with what happened," he said.
"The number of people living in this part of Russia is quite low except for those in a few towns and cities, such as Chelyabinsk. So, even a small change in the path of the meteor would likely have resulted in fewer casualties. In fact, the number of casualties we might expect for an asteroid of this size is very close to zero," he added.
However, Dr. Lewis also explained what might have happened if the meteor had arrived on the same trajectory but a few hours later: "The city of Newcastle-Upon-Tyne is at the same latitude as Chelyabinsk. Had the meteor arrived about four hours later, on the same trajectory, the blast wave could have had similar consequences for the UK city."
Dr. Lewis also used the NEOImpactor tool to investigate the possible consequences of larger asteroids colliding with the Earth. In the last month, the Earth has experienced an approach by the 330-meter asteroid 2004 MN4, also called "Apophis", and the smaller, 40-meter asteroid 2012 DA14, which made its closest approach just hours after the meteor over Russia.
For an asteroid the size of 2012 DA14, NEOImpactor estimated that 10,000 people could be affected, on average, if it impacted anywhere in the world. In contrast, an average of nearly one million people could be affected if asteroid Apophis were to collide with the Earth, with many more casualties arising if it impacted in a densely populated region.
In spite of the recent, dramatic demonstration of the risks posed by asteroids, there is reason to be optimistic about the future, Dr. Lewis said, "The human race already has the technology to deflect an asteroid if we are given sufficient warning."
In fact, Dr. Lewis is currently using the tools developed at the University within a European-wide project investigating mitigation options for the European Space Agency (ESA). The outputs from this work will help to support ESA's role in the global response to the asteroid threat.