What is the Largest Asteroid Ever to Hit Earth?
|
|
The largest asteroid ever to hit Earth was probably Theia, a Mars-sized body that formed over 4 billion years ago, during the early days of the solar system. Theia formed in a Lagrange point, a gravitationally stable region in the Earth's orbit, located on the opposite side of the Sun. Eventually, orbital fluctuations caused this body to oscillate closer and closer to the Earth, and eventually, they collided, throwing up a greater volume of molten rock than all the present-day continents combined. Some of this molten rock was ejected so forcefully that it entered orbit, aggregated, cooled, and became our Moon. This scenario is called Giant Impact Theory, and it accurately explains most features of the Earth-Moon system, such as why the chemical composition of the Moon is similar to that of the Earth's crust.
Since Theia, the largest asteroids known to impact the Earth were much smaller, maxing out at around 10 km (6 miles) in size. Larger asteroids may have hit the Earth during the period called the Late Heavy Bombardment, which occurred between 4.1 and 3.8 billion years ago. Because most of the crust from this period has either been subducted back into the mantle or covered in layers of sediment and volcanic rock, the largest asteroid craters may be hidden.
The largest verified crater on the Earth today is the Vredefort crater in South Africa, also known as the Vredefort Dome or the Vredefort impact structure. The crater is 300 km (186 mi) across, about twice the size of the Chicxulub crater, left behind by the asteroid that exterminated the dinosaurs. The Vredefort crater is thought to have been made by the largest asteroid to impact the Earth besides the one that created the Moon — strictly speaking, Theia was a planetoid rather than an asteroid — about 10 km (6 miles) in size. Realistically, these are the largest asteroids likely to impact the Earth. So, when you see mentions of asteroids "the size of Texas" in movies like Deep Impact, realize they shouldn't be taken too seriously.
The Wilkes Land anomaly, a concentration of mass under the Wilkes Land ice cap in Antarctica, may indicate an even larger impact structure, but at the time of this writing, its nature is uncertain.
|
Related wiseGEEK articles
Category
wiseGEEK features
Subscribe to wiseGEEK
|
6
anon20333, the Rocky Mountains are actually the second (known) mountain range to exist in that area. Both were caused but the Pacific crustal plate being subducted under, and uplifting, the North America Plate.
The Colorado River excavated the Grand Canyon while the Colorado Plateau was being up-lifted by the self-same subduction. - anon49077
5
To the poster expressing skepticism regarding formation of the Earth-Luna system.
Theia is just a theory that matches much of the known information about Luna. The moon is apparently made of that same material, in the same proportions, as Terra's crust. Terra, on the other hand, is short a significant amount of "rocky" material. In short, Earth's core is too large.
The theory is that Theia ripped off much of the Earth's crust and threw it into orbit. Earth's and Theia's crustal material ended up in Earth orbit while Theia's metallic core merged with Earth's. - anon49076
3
I don't like this idea of the Earth-Moon system as being of the same origin. To the best of my knowledge current scientific thinking would indicate that the moon was in fact a captured object about 1 billion years in to the Earth's early history? would somebody like to explain? - pmgleave
2
The largest crater on Earth is the Vredefort crater in South Africa with a diameter of about 180 miles, so a 1000-mile-wide crater in the United States seems unlikely. The largest crater in the United States is the Chesapeake Bay Crater in Virginia, just 56 miles across, and it is underwater. The largest terrestrial crater in the US is the Beaverhead Crater in Idaho, 37 miles across, which makes it one of the biggest on Earth. - anon20396
1
Check out the giant crater in the western quarter of the united states.Go to the mapquest satellite viewer and use the aerial mode to view the western United States. Zoom to the third level from the bottom. Check the labels box. Now, look at where Boise, Idaho is located. Just north east of Boise is a very large impact recoil peak. There is another recoil peak a little further north west of Boise/northeast of Baker City Oregon. Uncheck the labels box and look at the map without the roads, etc. Look carefully at the area to the east, over to the area of Yellowstone park and the northwest corner of Wyoming. To the north and south of the Yellowstone area, the crater rim is readily visible. Do this all with a smart student or a whole classroom if you can. (6th-8th grade). Follow the arc of the crater rim south.. to the south west, up to the north along the western Cascade Mountains up through Washington and then eastward around the Canada border and on down south to reconnect back at the Yellowstone area. The crater rim here appears to have been affected by Yellowstone caldera activity. See the big impact crater. About 1000 miles in diameter. There is more to the south. Look at the four corners area. See the super volcano. Ever wonder where the Colorado Rocky Mts. came from? Say, what about that crack running down the west wall of the western cone/caldera? Grand Canyon. - anon20333
|
Written by
Michael Anissimov
Last Modified: 17 October 2009
copyright © 2003 - 2009
conjecture corporation
