Impact!

- Demonstrate an appreciation of the potential consequences of a collision between an impactor and the Earth
- Describe how astronomers gather evidence of impacts between bodies within the Solar System and consider their effects.

Eugene Shoemaker and David Levy were comet hunters. They discovered what looked to be a squashed comet in the sky in the region of Jupiter, and after careful analysis it was found to be over 21 segments of a comet that was once one body. It was shattered when it orbited too close to Jupiter, and in 1994 each piece collided with Jupiter over the course of a day. Fireballs erupted from the gas giant and Jupiter was left with impact scars for some time afterwards.

If the same comet hit planet Earth it would cause enormous damage in the region where it landed, though its long term impact would be more dangerous still. The atmosphere would only protect us by disintegrating a small part of the comet. Whether or not it landed at sea, it would eventually hit the Earth’s crust at speeds of over 10,000 km an hour and jettison tonnes of material into the atmosphere. The Sun would be blocked from the sky by thick clouds over the entire surface. Agriculture would fail, temperatures would plummet. Human and animal life would starve and eventually all life would become extinct on Earth. It may take hundreds or thousands of years for the Sun to reappear and even longer for the climate to regain its former status, perhaps changing it permanently.

Scientists have shown Earth has undergone mass extinctions like this before, notably 65 and 250 million years ago. It is claimed an impact like this wiped out the dinosaurs.

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Questions

- What evidence is there that objects have hit other bodies like planets and moons in the past?
- Describe the impact of an object of either a small or large size hitting the Earth.

Activity

Research and compare the consequences of impacts at these locations in the past:
- Tunguska
- Chicxulub

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