Final answer:
If a 10 km NEO collided with Earth, it could cause global destruction by ejecting dust into the atmosphere, leading to diminished sunlight, climate disruption, and potential mass extinction.
Step-by-step explanation:
The question asks what would happen if a 10 km near-Earth object (NEO) collided with Earth. A collision of such magnitude would have dire consequences. Astronomers recognize the potential of significant damage from NEOs, which has prompted initiatives like NASA's Spaceguard Survey to track potential impactors. NEOs on a collision course with Earth pose a global threat, as seen 65 million years ago with the dinosaurs' extinction.
If a 10 km NEO collided with Earth, the amount of dust ejected into the atmosphere could block sunlight for months, disrupting global agriculture and climate, potentially leading to mass extinction. Previous instances have shown that even much smaller NEOs can cause substantial damage, such as the explosion equivalent to a 10-megaton nuclear bomb from a 60-meter NEO. It's also concerning that we only track a fraction of the smaller NEOs that could still destroy cities. The collision with a 10 km NEO, significantly larger than those currently tracked, would likely be a global catastrophe.