The fact that an asteroid impact hasn't wiped out mankind can be attributed to a combination of several factors, including probability, celestial dynamics, and the presence of protective mechanisms. Here are some key points to consider:
Probability and Frequency: While large asteroid impacts are rare events on a human timescale, they have occurred throughout Earth's history. However, the frequency of such catastrophic events is relatively low, allowing life to thrive on our planet for millions of years.
Size and Frequency of Impactors: Most asteroids in our solar system are relatively small, ranging from tiny fragments to objects several kilometers in diameter. The larger the asteroid, the rarer it becomes. The likelihood of a catastrophic impact is significantly lower due to the scarcity of large impactors capable of causing widespread devastation.
Planetary Defense Efforts: Scientists actively monitor and track near-Earth asteroids (NEAs) using various ground-based and space-based telescopes. Efforts such as NASA's Near-Earth Object Observations program focus on identifying potentially hazardous asteroids and predicting their future trajectories. This allows for early warning and the possibility of taking measures to mitigate potential threats if necessary.
Atmosphere as a Shield: Earth's atmosphere serves as a protective shield against small to moderately-sized asteroids. When an asteroid enters the Earth's atmosphere, it encounters resistance and friction, causing it to heat up and disintegrate. This process, known as atmospheric entry, significantly reduces the number of asteroids that reach the Earth's surface intact.
Impact Cratering: The Earth's surface bears the scars of past asteroid impacts in the form of impact craters. However, the majority of these craters are located in remote areas or underwater, minimizing their direct impact on human populations.
It's important to note that although the likelihood of a catastrophic asteroid impact is relatively low, the scientific community remains vigilant and continuously works to improve our understanding and preparedness for potential future events.