Cenote Ik-Kil (by chris-tina)
頭社晨霧 (by Clonedbird 克隆鳥 & Iris 艾莉絲)
Life on Mars!
Little spheres of rock, dubbed blueberries, like these ones are known to form with the help of liquid water and microbes on Earth. This might mean there was once life (and liquid water) on Mars that formed their Martian cousins! It was only recently discovered that microbes are part of the process - research that was done using equipment in Western Australia.
Image of the Martian blueberries courtesy NASA/JPL/Cornell University - taken with the Opportunity Rover.