CAN A COMET HIT OUR PLANET?
In remote area named Aorounga, in Chad, there are three craters in a row, each about 10 km in diameter it is believed this is a crater chain formed by the impact of fragmented comet or asteroid 400 million years ago. The main crater Aorounga South was known for many years. But a second and possibly third crater lay hidden until radar penetrated the ground, revealing their ragged outlines. The first crater chains were discovered by NASA voyager-1 spacecraft.
In 1979, when the probe flew past Jupiter moon Callisto, cameras recorded a line of craters. Eight chains were found on Callisto and three more on Ganymede. Initially the chains were puzzle. Were they volcanic? Had an asteroid skipped along the surface of Callisto like a stone skipping across a pond? The mystery was solved by in 1993 with the discovery of comet Shoe-maker-Levy 9, SL-9 was not a single comet but a string of pieces – a chain of 21 comet fragments created when Jupiter gravity ripped the original comet apart, SL-9 struck back in 1994, crashing in to Jupiter. Astronomers have since realized that fragmented comets and rubble –pile .Asteroid are common place. Comets fall apart easily; sunlight can shatter their fragile nuclei. Furthermore, there is mounting evidence that many seemingly solid asteroids are assemblages of boulders, dust and rock held together by gravity. They make chains.
In1994; researchers announced their finding of two crater chains on the moon. One, on the floor of the crater Davy, is spectacular-a perfect line of 23 pockmarks each a few miles in diameter. This proved the crater chains exist in the Earth-moon system. But where on Earth are they? Earth tends to hide its craters. Wind and rain erode them, sediments fill them I , and the tectonic recycling of earth crust bliterates them.Google Earth is a digital map of our planet.
Gonzlez began by calling up Keira impact crater inlibya the Sahara largest. Minutes later, two craters appeared. they had multiple rings and a central peak .At least one of the crater had never been catalogued before and both lined up with the Aorounga crater 200 km away;map.In less than two minutes The history of earth is shaped by impacts .Crater chains tell us important things about our planet.