Why People Thought "Aliens" Made These Rocks

Every so often, humans stumble across stones that are so bizarre and out of place that they seem like they were put there by something sentient. Are the Martian blueberries signs of life on Mars? Were the Klerksdorp spheres left by aliens? And what the heck are fairy stones?Let's look at three of the strangest rock types out there, what we thought they were, and what they really tell us about our planet's actual geology. Hosted by: Hank Green (he/him) ---------- Support us for $8/month on Patreon and keep SciShow going! https://www.patreon.com/scishow Or support us directly: https://complexly.