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Large asteroid collisions with Earth are very infrequent, but when they occur their effects on the planet’s climate can be devastating. The extent of an asteroid’s effects has to do in part, with its size, which can vary from very small (pebble or baseball-sized) to gigantic: the asteroid Ida, pictured above, has dimensions of roughly 35 x 13 x 15 miles, and has a small moon which orbits around it! (The moon, Dactyl, is visible in the right side of the image.)

Though infrequent, asteroid impacts have likely been the causes of the most devastating catastrophes to afflict the Earth, including triggering the several mass extinctions that have occurred throughout the 3.7 billion year history of life on the planet. Large asteroid impacts effect the Earth’s climate in several ways over different time scales:



Large asteroid collisions with Earth are very infrequent, but when they occur their effects on the planet’s climate can be devastating. The extent of an asteroid’s effects has to do in part, with its size, which can vary from very small (pebble or baseball-sized) to gigantic: the asteroid Ida, pictured above, has dimensions of roughly 35 x 13 x 15 miles, and has a small moon which orbits around it! (The moon, Dactyl, is visible in the right side of the image.) Though infrequent, asteroid impacts have likely been the causes of the most devastating catastrophes to afflict the Earth, including triggering the several mass extinctions that have occurred throughout the 3.7 billion year history of life on the planet. Large asteroid impacts effect the Earth’s climate in several ways over different time scales:

	When an asteroid arrives at Earth, it is traveling at very high speed and as it passes through the atmosphere, significant amounts of heat are generated. This causes short-term warming of the atmosphere.

	When the asteroid strikes the Earth’s surface, hot debris is thrown into the atmosphere, further heating it.

	This heat causes either local or global wildfires, depending on how large the impact is, and the burning vegetation contributes more debris, in the form of soot, into the atmosphere.

	The soot that enters the atmosphere from the burning vegetation and the original impact can remain there for days to years. This debris is usually washed out of the lower atmosphere by rain within weeks, but in the upper atmosphere, where there is no rain, it stays until pulled down slowly by gravity. All this soot in the atmosphere blocks sunlight, causing the Earth’s climate to cool over periods of up to a few years.

	The soot that is washed out of the lower atmosphere contributes to acid rain, which acidifies the oceans.

	The debris that entered the atmosphere also leads to increased CO2 levels, which will cause global temperatures to increase over decades to centuries until vegetation grows back and is able to lower CO2 levels. However, vegetation may not be able to lower CO2 to pre-impact levels.