Asteroid 2005 YU55 is the size of an aircraft carrier and flew past Earth the morning of November 8, 2011. NASA scientists and astronomers throughout the world said there was no danger of asteroid 2005 YU%% hitting the planet, but a Purdue University asteroid impact expert says that if a similar-sized object actually hit the Earth, it would result in a 4,000-megaton blast, a magnitude 7.0 earthquake and, should if it struck in the deep ocean, would cause a 70-foot-high tsunami wave 60 miles from the splashdown site.
NASA scientists reported this morning that asteroid 2005 YU55 passed between the orbits of the Earth and the Moon and came within 201,000 miles of Earth on its closest approach.
Jay Melosh, an expert in impact cratering and a distinguished professor of earth and atmospheric sciences, physics, and aerospace engineering at Purdue University, said the asteroid's orbit and trajectory meant there was zero chance of an impact. Melosh said.
“What is unique about this asteroid flyby is that we were aware of it well in advance. Before about 1980 we wouldn’t know about an asteroid of this size until it was already making a close pass, but now it is unlikely that such an asteroid will approach the Earth without our knowledge.”
NASA’s Near Earth Object Program, or NEO, celebrated a milestone earlier this year by announcing that current search programs have discovered more than 90 percent of near-Earth objects more than six-tenths of a mile in diameter. A larger number of smaller objects have yet to be found, however. At the end of August 2011, NEO had discovered over 8,000 near-Earth objects. Over 450 of known near-Earth asteroids discovered to date are 1 kilometer in size or greater.
Spacewatch, a program created to discover and track all large asteroids crossing the Earth’s orbit, discovered YU55 in 2005. This close approach had been expected since then, he said.
Melosh used the asteroid impact effects calculator he developed to estimate what would happen if the asteroid, which is a quarter mile in diameter, hit the Earth. The calculator, "Impact: Earth!" allows anyone to calculate potential comet or asteroid damage.
Users first enter a few parameters, such as:
- Diameter of the approaching object.
- Density of the object.
- Velocity of the object.
- Angle of entry.
- Impact point on Earth.
The site then estimates the consequences of its impact, including the atmospheric blast wave, ground shaking, size of tsunami generated, fireball expansion, distribution of debris and size of the crater produced. The calculator is available at http://www.purdue.edu/impactearth
For example, YU55 would strike with a velocity of 11 miles per second. Although it would begin to disintegrate as it passed through the atmosphere, the fragments would strike in a compact cluster that would blast out a crater 4 miles in diameter and 1,700 feet deep, Melosh said. Sixty miles away from the impact site the heat from the fireball would cause extensive first-degree skin burns, the seismic shaking would knock down chimneys and the blast wave would shatter glass windows.
If YU55 were to strike a large city like Chicago, it would obliterate the entire city and leave few survivors. Fortunately, the chance of a large impact targeted on a city is very small, he said.
According to NASA, the last time an asteroid this size came close to Earth was in 1976, and the next known approach of such a large asteroid will be in 2028.
Meteor Crater, located near Winslow, Arizona, is the result of a collision between an asteroid traveling at 26,000 miles per hour and planet Earth approximately 50,000 years ago. Meteor Crater is nearly one mile across, 2.4 miles in circumference and more than 550 feet deep. To give you a perspective, if asteroid 2005 Yu55 had hit Earth, it would've caused a crater 4 miles wide and 1,700 feet deep. (Click Image To Enlarge)
Collisions of asteroids with Earth are quite common and occur about every 100,000 years on average. The following worldwide map shows the location of impact caters caused by asteroids colliding with Earth. There are probably hundreds more craters hidden in our vast oceans. As you can see, the United States has been hit quite frequently over time.
The most recent impact of this size is not known, but there are about 20 similar craters known in the geologic record, including the Wetumka crater in Alabama and the Rock Elm crater in Wisconsin. Of the known large craters, the most recent are the six-mile-wide Bosumtwi crater in Ghana, which is about 1 million years old, and the nine-mile-diameter Zhamanshin crater in Kazakhstan, which is about 900,000 years old, Melosh said.
"Impacts from asteroids of this size are very rare. They occur about once every 100,000 years, so the chances of an actual collision with an asteroid like YU55 is about 1 percent in the next thousand years. Apophis, a similar-sized asteroid about one-third of a mile in diameter is the biggest threat in our near future. It has a tiny chance of striking the Earth in 2036."
Melosh is a co-author of a 2010 NRC report “Defending Planet Earth” that explores the feasibility of detecting all Earth-crossing asteroids down to a diameter of 140 meters, or about one-tenth of a mile, and of ways to mitigate their hazard.
COMMENTARY: In a previous blog post dated November 8, 2011, I mentioned to you that asteroid 2005 YU55 passed us at a distance of 201,000 miles from Earth, but the potential danger is still not over, 2005 YU55 will return for a second near-Earth approach in 2028. Some astronomers believe that the asteroid's second pass will take it beneath the orbit of our space satellites, and could even skim off of Earth's upper atmosphere creating friction and displaying one incredible tail of flame and sparks. There is also a possibility that asteroid 2005 YU55 could collide with Earth, but we won't know for sure until NASA scientists have analyzed the most recent data and recalculated its new orbit and orbital track when it returns in 2028.
On Friday, April 13, 2036, asteroid 2005 YU55 will make a third near-Earth visit. That's the date that has many astrophysicists and astronomers concerned, since we don't know whether it will be on a collision course with Earth. It is obbvious that NASA and the other nation's must cooperate and work together to take corrective actions to either destroy or redirect the orbits of astroids like 2005 YU55 in order to avoid a catastrophic or extinction-level event (ELE).
If you were wondering what it might be like if a large asteroid were to actually hit Earth, it would definitely be an "Oh, Shit!!" moment like in the following video:
Courtesy of an article dated October 31, 2011 appearing in the Purdue University University News Service and an article dated November 3, 2011 appearing in the Purdue University University News Service