Death of our planet

Asteroid impacts and supernovae.

Asteroids are rocky and metallic objects that orbit the Sun but are too small to be considered planets. An asteroid impact with the Earth is always on the cards. Asteroids have hit Earth in the past, but unlike the Moon, evidence of such impacts has been weathered away. A number of Earth's mass extinctions millions of years ago are linked to such impacts. The most famous asteroid impacted about 60 million years ago and caused the extinction of the dinosaurs. Nothing bigger than a chicken could survive the altered environment that resulted after the impact.

 


Asteroid Gaspra, as viewed from the Galileo spacecraft. Galileo, while on its way to Jupiter, encountered Gaspra on October 29, 1991. Gaspra is approximately 19 kilometres across.

 

Death of the dinosaurs but life on earth continues.

NASA scientists have predicted that a 10 km rock strikes earth every 100 million years. There are many asteroid orbiting around the sun potentially capable of crashing into Earth. However this does not mean that all life will become extinct.

Earth is no stranger to catastrophic collisions with astronomical objects. In fact, 65 million years ago an asteroid, 300 km wide, crashed through our atmosphere and slammed into, what is now, the Gulf of Mexico. The impact was so violent that it liquefied rock and sent earth quakes reverberating around the planet. Giant tsunamis traveled at great speeds across the oceans while huge clouds of dust and rock were blasted high into the atmosphere blocking out sunlight.
Photosynthesis ceased as months of darkness followed. Many of the larger animals simply perished as their food source dried up. Smaller animals, such as mammals that were struggling to compete with the dinosaurs now flourished.

Why did the large herbivores die first?

Why did the mammals thrive in conditions that wiped out there dinosaur rivals?
Such events are not the domain of prehistoric time but frequently occur during modern times with devastating influence. In 1908 an asteroid exploded over Tunguska in Siberia. Even though this asteroid did not hit the ground the explosion flattened over 2,200 sq kilometres of Siberian forest. If the asteroid had hit the ground its devastation would have rivaled that of a large nuclear bomb. For this reason NASA has set up the Near Earth Object Program to monitor near Earth objects large enough to cause catastrophic damage upon colliding with Earth. If a situation was to occur 50 years ago we would be powerless to prevent the devastation. However, with the development of powerful rockets and nuclear devices we may be able to deflect an approaching asteroid.
Some 440 million years ago a mass extinction occurred known as the Ordovician extinction. Some scientists believe that this was caused by a supernova some 10,000 light years away.
How often does a large asteroid strike Earth?
What is the Near Earth Object Program?
Why did NASA initiate this program?
Supernova