The impact of an 800-meter asteroid on Earth would have significant global consequences, but it is unlikely to cause the complete extinction of all life on the planet. The effects of such an impact would depend on several factors, including the composition and velocity of the asteroid, as well as the location of the impact.
If an 800-meter asteroid were to collide with Earth, it would release an enormous amount of energy upon impact. The immediate effects would include a massive explosion, generating shockwaves, and intense heat. The impact would likely cause widespread destruction in the vicinity of the impact site, causing fires, earthquakes, and tsunamis if the impact occurred in an ocean.
The release of dust, debris, and gases into the atmosphere would have global consequences. The ejected material would be injected into the upper atmosphere, blocking sunlight and causing a temporary reduction in global temperatures. This phenomenon, known as an impact winter, could disrupt the food chain, leading to the collapse of ecosystems and potentially causing widespread famine.
However, the extinction of all life on Earth would require an event of much greater magnitude, such as the impact of a significantly larger asteroid or a series of catastrophic events occurring simultaneously. The planet has experienced large asteroid impacts in the past, most notably the event that led to the extinction of the dinosaurs approximately 66 million years ago. While devastating on a global scale, life on Earth eventually recovered and diversified.
It's worth noting that significant efforts are being made to detect and track near-Earth asteroids and develop strategies to mitigate the potential threat they pose. Astronomers and space agencies around the world are actively working on technologies to divert or destroy potentially hazardous asteroids to minimize the risk to our planet.