DEADLY ASTEROID CLOSE CALLS

Asteroid 2024 YR4 may not be the serious threat it was once thought to be, but scientists are still concerned about the possibility of future asteroid collisions

- ANDREW MAY

As Earth travels through space, it’s constantly colliding with anything that crosses its path. This ranges from extremely small objects to much larger ones, with far more of the former than the latter. At the small end of the spectrum are tiny particles of cosmic dust, much too small to be seen without a microscope, that end up in gutters and drains. At a larger scale are the rock-like meteorites sometimes seen in museums – small chunks of asteroids that have survived the journey through Earth’s atmosphere. This journey slows them down to relatively modest speeds, so even if they hit a car or building when they reach the ground, they rarely do much damage. Their main significance is scientific in what they can tell us about the nature and composition of interplanetary material.