Asteroids, the threat...
Our most close neighbours
|Automatic translation||Updated June 01, 2013|
The interplanetary space is far from being empty, it is sprinkled with dusts and with mater dating the creation of the solar system.
Asteroids being our most close neighbors, they are somehow, bound to our fate. Those who cross our orbit are called geocruisers. Astronomers considered the trajectories of asteroids susceptible to terminate millions of human lives on our planet. Apophis is an asteroid of small size because it is 250 meters wide and could represent a threat. We estimate at present at a chance on 45 000 the probability that this pebble comes to crash in the Pacific Ocean on April 13th, 2036.
What an asteroid?
An asteroid is a not observable heavenly object in the bare eye because of its small size which varies some tens of meters in several hundreds kilometers in diameter. They are a part of our solar system and turn around Him. The objects of less than 50 m of diameter are called by meteorites. Those are not satellites of planets but fragments of the disk proto planetary which did not manage to group together in planets during their formation. Asteroids have a big importance in the understanding of the formation of the solar system, it is for that reason that the astronomers show a strong interest in the study of these objects. The first asteroid was accidentally discovered on December 31st, 1800 by Giuseppe Piazzi, director, in the period, of the observatory of Palermo, in Sicily. While observing the constellation of the Taurus, he perceived a not identified object moving very slowly in the night-sky.
Piazzi named him Ceres, of the name of the Greek goddess who makes take out the sap of the ground and who grows the young shoots in spring. Between 1802 and 1807, three other bodies were discovered: Pallas, Juno and Vesta.
Image: The details of Eros seen by the probe NEAR which settled without damage on the asteroid, on February 12th, 2001.
Zones with asteroids
Between Mars and Jupiter (from 300 to 600 million km of the Sun).
Asteroids are mainly situated in the main belt, between the orbits of Mars and Jupiter. We find several hundreds of thousand listed objects there. All its objects would have been able to form a planet in this zone but the gravitational disturbances of Jupiter did not allow it. Jupiter played defender's role of the life on our planet. Without Jupiter, the bombardment on Earth would be 1000 times as frequent.
In the belt of Kuiper (between 35 and 100 UA of the Sun).
This zone contains ice-cold objects, and are not thus strictly speaking asteroids. This belt is rather a crèche of comets. The first member is discovered in 1992.
In the cloud of Oort (between 20000 and 150000 UA neighborhood).
This zone of the sky, the remainder of the original nebula, would contain billions of nuclei of comets and would be the source of most of the new comets which enter the central regions of the solar system.
The big bombardment
It falls even today on the surface of the Earth several thousand tons of mater from the space. It is about interplanetary dusts.
The risk of a major impact began to invade the consciences at the beginning of 1980s, when the scientific community had the first proofs that such a cataclysm had already occurred repeatedly in the story of the Earth.
It already arrived several times and the life every time, disappeared in 90%. The geologists demonstrated that the cause was there, a collision with an asteroid. We know how to estimate this risk today.
Let us enlarge the object by 10, it makes then 500 meters in diameter. The energy to be dissipated is 1 million bigger times. The atmosphere would then be pierced and the object would provoke a gigantic tidal wave killing several hundreds of thousand persons on the American and Asian coasts. With 5 kilometers in diameter its impact would be a more powerful billion times and would have engendered an apocalypse deserving of the worst divine punishments.
Disintegration of meteorites...
An asteroid of 1 to 3 meters in diameter that enters the atmosphere does not cause any damage because a total disintegration occurs during passage through the atmosphere.
Image: Asteroid against this, weighed 80 tones with a diameter of about 4.1 meters. Age = recent,
An asteroid 60 meters in diameter which enters the atmosphere with a too weak angle of incidence (some degrees), does not manage to cross the atmosphere and does not provoke damage.
It occurred on 10/08/1972 in the sky of the Montana in the North of the United States.
Image: This meteorite is in fact a small asteroid 60 meters in diameter, which crossed the sky of the Montana on August 10th, 1972 before bouncing on the atmosphere and getting lost in the space.
Once every 1 000 years...
An asteroid 75 meters in diameter would provoke a crater 1700 meters in diameter and would destroy a city as Paris by killing 5000 persons.
The probability that it arrives is once every 1 000 years.
Image: Meteor Crater, Arizona. Wikimedia Commons
Age = 50 000 years,
Once every 45 000 years...
An asteroid 350 meters in diameter would provoke a crater 6000 meters in diameter and would destroy a zone as Ile-de-France by killing 500 000 persons.
Image: The crater filled with water of Sääksjärvi in FinlandAge = 560 million years,
Diameter of the crater = 6 kilometers,
Diameter of the meteorite = 300 meters
Once every 63 000 years...
An asteroid 700 meters in diameter would provoke a crater 12 kilometers in diameter and would destroy a zone as a quarter of France by killing 1,5 billion persons because of the tsunami activated on the scale of a ground hemisphere.
The probability that it arrives is once every 63 000 years.
Image: The crater filled with water of Dellen in Sweden.Age = 89 million years,
Diameter of the crater = 19 kilometers,
Diameter of the meteorite = 1 km.
Once every 250 000 years...
An asteroid 1700 meters in diameter would provoke a crater 30 kilometers in diameter and would destroy a zone as France by killing 1,5 billion persons because of the tsunami activated on the scale of a ground hemisphere and of the modification of the climate which would follow itself with disappearance of the ozone layer.
The probability that it arrives is once every 250 000 years.
Image: Ries Crater in Germany. The stones of the Church of Nordlingen, located at the center of the Ries crater, was carved into a rock called impact suevite (rock formed by meteorite impact on Earth).Age = 15 million years,
Diameter of the crater = 24 kilometers,
Diameter of the meteorite = 1,2 km.
Once every 1 000 000 years...
An asteroid 3 kilometers in diameter would provoke a crater 60 kilometers in diameter and would destroy a zone as France and its nearby countries by killing 2,5 billion persons because of the tsunami activated on the scale of a ground hemisphere, of the modification of the climate and the fires.
The probability that it arrives is once all the million years.
Image: Crater of Manicouagan, Quebec.
Age = 210 million years, average
Once every 10 000 000 years...
An asteroid 7 kilometers in diameter would provoke a crater 125 kilometers in diameter and would destroy a zone as Europe by killing 3 billion persons because of the tsunami activated on the scale of a ground hemisphere, of the modification of the long-term climate and the fires.
The probability that it arrives is once every 10 million years. We reach here an extinction of mass.
Image: Crater of Popigai, Siberia.
Age = 40 million years, average
Once every 65 000 000 years...
An asteroid 16 kilometers in diameter would provoke a crater 200 kilometers in diameter and would have a world repercussion by killing 6 billion persons because tsunami activated on the scale of the planet, and modification of the climate with very long term.
The probability that it arrives is of time every 100 million years. Extinction of mass as the one that there was there is 65 million years provoking the disappearance of dinosaurs and 90 % of the sorts.
Image: Crater of Chicxulub, Mexico
Age = 65 million years, average
Millions of asteroids frequent the region of the space between Mars and Jupiter.
Image: Artist image