Earth was hit many times by asteroids

If Earth were to be hit by massive asteroid in years to come there could be even a chance of complete destruction of all life on our planet, including our own.  In its past, Earth was many times hit by large asteroids, and scientists are constantly finding new impact crates sites.

Up to now, there has been discovered around 180 impact crater sites. Up to recently the largest and oldest known crater was the 300 kilometre wide Vredefort crater in South Africa, 2 billion years in age.

The latest study by EU scientists has discovered the oldest crater in Greenland,  estimated to have occurred between 3 and 4 billion years ago.This is a 100 kilometre-wide crater located near the Maniitsoq region of West Greenland.. It took scientists three years to gather enough evidence that convinced the scientific community that this is an indeed a giant impact crater.

This discovery should greatly benefit science by enabling them the insight into the effects of cratering on the Earth in such distant past. Scientists have also reported that they were extremely lucky to find this crater, given the astronomically low chances as the result of erosion and covering by younger rocks.

In a very distant past Earth often experienced collisions with asteroids, primarily because it had much bigger gravitational mass.

Asteroids are not only potential doomsday carriers, the craters where impact took place are often the source of many elements and minerals or oil and gas.

One Canadian company is already using the impact model to explore for deposits of valuable nickel and platinum metals at Maniitsoq.

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Interesting facts about asteroids

Asteroids, also called planetoids, are small Solar System bodies orbiting the Sun.

The main difference between asteroids and planets is that asteroids never grew large enough to become planets.

In the orbits of the planets Mars and Jupiter is the largest group of known asteroids - the area known as the asteroid belt. It has been estimated that asteroid belt contains between 1.1 and 1.9 million asteroids larger than 1 km (0.6 mi) in diameter.

The first asteroid discovery in history occurred in 1801 with the discovery of asteroid Ceres, by Giuseppe Piazzi, though it was considered a planet at the time. Ceres is currently the largest known asteroid.

Astronomers at the University of Tennessee, Knoxville, believe that about 20 percent of asteroids have their own moons just like planets do.

The NASA scientists believe that giant black hole at the center of the Milky Way may be vaporizing and devouring asteroids.

In November 2011 an asteroid the size of an aircraft carrier safely flew past our planet. The next known approach of an asteroid this size will be in 2028.

The difference between asteroids and comets is that asteroids are rocks that primarily circle the Sun between the orbits of Mars and Jupiter while comets on the other hand tend to have highly elliptical orbits taking them from the frozen extreme edges of our Solar System to within distances so close to the Sun that solar radiation causes material in the comet to vaporize and stream out, forming the characteristic comet's tails.

The scientists study asteroids primarily because they believe that their samples might give them better clues in explaining our solar system's formation and how life began on our planet. This is the main reason why asteroids are the primary goals of many robotic missions.

Asteroids are in fact leftovers that originated from the cloud of gas and dust (the solar nebula). The solar nebula is believed to have collapsed to form our sun and the planets about 4.5 billion years ago. According to this theory asteroids contain the original material from the solar nebula, and can therefore provide us with the information about the conditions in times of our solar system's birth.

Huge asteroid hitting the Earth is one of the main themes of many Sci-Fi movies, This scenario could also at some time in future occur in reality, causing massive damage to our planet. Many scientists believe that the last time huge asteroid hit the Earth it killed all the dinosaurs and most other life on our planet.

The scientists are already looking at potential defensive systems against huge asteroids going our way. British scientists for instance believe that we should build large spacecrafts (so called gravity tractors) in order to stop large asteroids from hitting the Earth.

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Huge asteroid hitting the Earth - What would happen?

A huge asteroid hitting the Earth was main theme of many Sci-Fi movies, and both the filmmakers as well the scientists agree that such hit would cause enormous disaster on our planet. The last time huge asteroid hit the Earth it killed the dinosaurs, the largest creatures ever on land, and if such scenario would to happen again it would again destroy many species on our planet.

Gregory L. Matloff, NASA researcher and New York City College of Technology, has for many years researched the possible impacts of asteroids hitting our planet, and most notably the best ways to avoid such a scenario. He believes that the best solution to avoid such scenario is to change the trajectory of the asteroid or in alternate case to destroy it.

In not so far future or to be more precise in 2029 and 2036, the asteroid called Apophis (named appropriately after the Egyptian god of darkness), having at least 1,100 feet in diameter, 90 stories tall, and weighing an estimated 25 million tons, will make two close passes by Earth at a distance of about 22,600 miles.

The impact of this asteroid (traveling at an estimated 30,000 to 40,000 miles) hitting the earth would cause total disaster, in fact it would strike our planet with 68,000 times the force of the atom bomb that leveled Hiroshima.

Many scientists agree that the potential impact with Apophis is very unlikely but even avoiding the impact itself doesn't exactly free us of danger because there is a possibility that when Apophis passes in 2029, heating as it approaches the sun, it could fragment or emit a tail, which would act like a rocket, unpredictably changing its course. Scientists also warn that if Apophis or its remnants enter one of two "keyholes" in space, impact might happen when it returns in 2036.

The best way to avoid impact with such objects is to try to change their trajectory though some would no doubt prefer the method of "lets blast em". The latter method could result in a radioactive shower from the debris, and this is certainly something we wouldn't like to see.

But how to change the trajectory of asteroid? Dr Matloff explains that this can be done by heating its surface to create a jet stream, which would alter its trajectory, causing it to veer off course. In theory this could be done with the help of a solar collector (SC), which is a two-sail solar sail configured to perform as a concentrator of sunlight.

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How to protect our planet from asteroids?

An Armageddon in form of big asteroid hitting Earth and destroying all life on Earth is well known topic seen in many popular movies and novels. But this is sadly not just in science fiction sphere but could also turn out to be reality somewhere in future. Therefore scientists are already working on plans to protect our planet from large asteroids. One of the very interesting defensive concepts is the plan coined together by British scientists and engineers in form of spacecraft that could stop large asteroids from hitting the Earth.

They believe how the 10-tonne spacecraft that would rely on the force of gravity would be more than capable to deflect any asteroid years before any potential collision could happen. If we take a look at NASA website we can see that they have recorded 1068 known "Potentially Hazardous Asteroids", and there are probably much more hazardous asteroids in space.

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