system
Given the following post, respond as if you're commenting on Reddit:
human
What is in a rain drop besides water?

When a rain drop is already formed and falling to the ground, is there anything in the drop besides water? Like microscopic organisms or specs of dust or anything else?
gpt
Rain drops need something to nucleate off of to condense. This can be anything from a speck of dust to soot from forest fires to sulfur dioxide particles from volcanoes. They'll also react with CO2 in the atmosphere to form a very weak carbonic acid.