
Think of an object made of iron: An I-beam, a car frame, a nail. Now imagine that half of the iron in that object owes its existence to bacteria living two and a half billion years ago.
Think of an object made of iron: An I-beam, a car frame, a nail. Now imagine that half of the iron in that object owes its existence to bacteria living two and a half billion years ago.
Planet Earth is situated in what astronomers call the Goldilocks Zone -- a sweet spot in a solar system where a planet's surface temperature is neither too hot nor too cold.