THE BIRTH OF OUR PLANET

How a cosmic cloud gave rise to life

The Solar System was born from a cloud of dust called a nebula. A shock wave, triggered by the death of a nearby star, caused that nebula to collapse. It tumbled in on itself, forming a hot, white ball of matter that became so dense that atoms at its core started to fuse. These nuclear reactions gave birth to the Sun. Around that young star, the rest of the cosmic dust from the nebula continued to swirl. It formed small clumps that started to grow by a process called accretion. These clumps became the planets and moons.

The formation of the planets took millions of years, and it wasn’t peaceful. As Earth was beginning to take shape, large chunks of rock and ice were still hurtling through the Solar System. They would crash into Earth at random, melting the ground and sending violent shock waves into the mantle. The biggest of these collisions was with a planet-sized rock called Theia, which formed our Moon. Though devastating, that encounter played a vital role in the evolution of our planet. It stabilised Earth’s rotation, helping to steady the climate, and it created the tides.

By the time Earth started to cool, most of its water had boiled away into space, and in the early years it didn’t even have an atmosphere. Luckily, another planet was on hand to help. Jupiter sits just beyond the asteroid belt. Its massive gravitational influence slows passing rock fragments, pulling them into orbit around the Sun. It acts as our protector, but also as a slingshot, sending some of those asteroids and comets right into our path.

The projectiles Jupiter hurled at our planet in the early years of the Solar System were full of hydrogen and oxygen, the raw ingredients of water. These elements melted into the mantle and came out as rain when ancient volcanoes erupted, turning the bare rocks of early Earth into mineral-rich oceans.