Earth's magnetic field and oxygen levels have increased more or less in parallel over the past 540 million years, suggesting the two factors are linked in some way, researchers say.

Low iron levels can flip the genetic switch on a mouse's sex during development, causing XY embryos to grow female features. But it's not clear whether the effect applies to humans.

Researchers armed with the Hubble Space Telescope have revealed that some of Uranus' largest moons have one side brighter than the other — but not the side they were expecting.