THE LASTING EFFECT

The effects of the bombardment can be seen in more than just the craters left behind

Titan

Saturn’s largest moon, Titan, is now covered in a thick nitrogen atmosphere but it’s unclear when this was created – during the moon’s formation or at a later date. If it formed with the moon, then it must have been much thicker as the bombardment would have blasted much of the gas away. Alternately, it could be that the bombardment provided the energy needed to liberate the gas from ammonia ice on the moon’s surface.

Mercury

The Caloris Basin, the largest impact basin on Mercury, was formed during the late heavy bombardment. The collision that created the 1,550kmwide site is thought to have been strong enough that it sent shockwaves through the entire planet, creating an undulating terrain on Mercury’s other side. It’s also been supposed that the impact could have kickstarted volcanic activity on the planet, which created its smooth plains.

Ganymede

Despite being similar in size and composition, Jovian moon Ganymede is very different from its sister, Callisto. While the former has a tectonically evolved surface and a differentiated core, the latter does not. One explanation is that a giant impact struck Ganymede, but not Callisto. The energy from this collision enhanced geologic processes, causing a fully separated iron core and subsurface ocean to form.

Mars

Bombardment would have melted Mars’s subsurface ice and produced enough heat to create a temporary climate that might have had the right conditions for life to start. Unfortunately, such conditions would have only lasted a few million years, before the constant shelling began to erode away more atmosphere than it created. By the end of the era, Mars was the cold and dry planet that we recognise today.