2.3 billion years
Earth’s magnetic field shuts down
The freezing of Earth’s outer core shuts down Earth’s magnetic field, with drastic consequences for any remaining life on the planet as there is nothing to deflect the DNA-damaging, potentially deadly cosmic rays and solar wind. The latter would also strip away any remaining atmosphere, leaving the surface totally defenceless.
2.8 billion years
Entirety of Earth is scorching hot
By this point Earth’s environment is hostile to any multicellular life, but when global temperatures – even at the poles – reach an average of 147 degrees Celsius (297 degrees Fahrenheit), even the last remaining unicellular life on the planet – in isolated refuges such as high-altitude lakes or cold-trap caves – can no longer survive.
3 billion years Moon becomes unstable and Earth’s poles become chaotic and extreme
The Moon has long been moving away from Earth – at roughly four centimetres (1.6 inches) a year – but this is the point at which it is sufficiently distant to no longer effectively influence Earth’s axial tilt, resulting in the planet’s true poles increasingly ‘wandering’ as its spin becomes less stable.
3.3 billion years Mercury or Venus could collide with Earth
There is a one to two per cent chance that Jupiter’s long-term gravitational influence on the inner Solar System makes Mercury’s orbit so eccentric that the small inner world might collide with the gassy Venus or even come as far as Earth, crash into the Sun or be ejected from the Solar System entirely.
3.5 to 4.5 billion years Surface heats to 1,130 degrees Celsius (2,066 degrees Fahrenheit)
Water vapour in Earth’s lower atmosphere increases to 40 per cent. This, combined with the Sun now being 40 per cent brighter than in the 21st century, leads to a rampant runaway hothouse environment with surface temperatures hot enough to melt rock. Essentially it’s a hotter version of today’s Venus.
7.5 billion years Earth and Mars become tidally locked with an expanding subgiant Sun
Having one side of a planet constantly facing the
Sun leads to more than just temperature differences between the two sides; any remaining atmosphere will necessarily move between the light and dark faces, creating storms and causing serious landscape erosion – not good for continued life in any form.
7.59 billion years Moon falls towards Earth, breaking into debris that rains on it
Orbital drag in the vicinity of the Sun’s apparent surface – the photosphere – reduces the Moon’s orbit until it reaches the point where the gravity holding it together is weaker than the tidal forces pulling it apart. Earth will again briefly have a ring of debris before it falls down on the planet.
7.59 billion years Earth falls into the Sun at red giant phase
Reaching its maximum size as a red giant – a radius 256 times its present-day value – the Sun swallows up Mercury and Venus, very likely Earth and possibly even Mars. On the plus side, by then Saturn’s moon Titan will likely have the precise surface temperatures needed to support life.