system
Given the following post, respond as if you're commenting on Reddit:
human
Why is it that certain elements are common in asteroids, e.g. iridium, but rare on Earth?
gpt
in the case of iridium it is really really dense and a lot of it descended deep into the earth when the earth was young, so much of our iridium is closer to the core than on the crust. the same is probably true for any element that is really dense.