Andrew Cohen - 23 May

Pluto / Alamy Stock Photo

Meteor showers are not uncommon, but as most meteors are smaller than sand grains, they disintegrate before hitting the Earths surface.

The interdependent nature of the Solar System has become more evident as we have begun to understand its history. It is tempting to imagine that the physical layout of the planets is a fossilised remnant of primordial patterns in the collapsing dust cloud around the newly ignited Sun 4.6 billion years ago, but our exploration of the planets, coupled with increasingly powerful computer simulations of the evolution of the Solar System, has revealed that this is not the case. Planetary orbits are prone to instability; particularly so in the early, more chaotic years when our Solar System was young. The details of precisely how the planetary orbits have shifted are still uncertain, but we now suspect that Mercury, the innermost planet, began life much further out and was deflected inwards to its present-day seared orbit. Jupiter and Saturn may have drifted inwards shortly after their formation, before reversing their course and retreating, but not before affecting the distribution of material out of which Mars and Earth would later form. Around the time that life began on Earth, Neptune and Uranus may have been flung outwards, disrupting the orbits of billions of smaller objects far from the Sun. The record of this time of unprecedented violence, known as the Late Heavy Bombardment, is written across the scarred surface of the Moon, itself most likely formed in a glancing interplanetary collision between Earth and a Mars-sized planet 4.5 billion years ago. The planets are like snowflakes; the detail of their structure their composition, size, spin and climate are a frozen record of their past.