Impact on earths enviroment 3rd Fact

(Source 1.) Link : http://www.earthsky.org/teachers/topic/environmental-impactAn impact event is the collision of a large meteorite, asteroid, comet, or other celestial object with the Earth or another planet. Impact events have been a plot and background element in science fiction since knowledge of real impacts became established in the scientific mainstreamin the environment refer to the sources, environmental behaviour and effects of actinides in Earth's environment. Environmental radioactivity is not limited solely to actinides; also, actinides such as uranium and radium specifically are of note.

(Source 2.) Link : http://www.nasa.gov/vision/earth/environment/ice_sheets.html In the most comprehensive survey ever undertaken of the massive ice sheets covering both Greenland and Antarctica, NASA scientists confirm climate warming is changing how much water remains locked in Earth's largest storehouse of ice and snow.

(Source3.) Link: http://www.environmentalgraffiti.com/sciencetech/10-greatest-major-impact-craters-on-earth/1403 Some 49,000 years ago a large nickel-iron meteorite “just” 150 ft across, weighing several hundred thousand tons (~300,000) and traveling at a speed of 40,000 miles per hour, hit Earth. The result of this meteor lies 55 km east of Flagstaff, Arizona and is called the Barringer Crater: the best preserved impact crater ever. The force generated by the impact was equal to the explosion of 20 million tons of TNT. Picture that.
It measures 0.75 miles (1.2 km) across, is 575 ft (175 m) deep and has a rim 148 ft (45 m) higher than the surrounding plain. Discovered in 1902, the Barringer Crater was named after Daniel Barringer, a successful mining engineer. Today it is still owned by his family and is also known as Meteor Crater, Coon Butte, and Canyon Diablo.

Possiblity i would say maybe