Alex McColgan

To help you imagine just how crazy that is, think of this.

Mount Everest doesn't even quite stretch to nine kilometers.

The impact that created this epic crater was a cataclysmic event that brought Mimas to the very brink of destruction.

Simulations suggest that if the impact had been just a little bit larger, or moving slightly faster, Mimas would have shattered completely, reduced to just another ring of debris orbiting Saturn.

Luckily for us though, the moon survived.

Shockwaves from the impact travelled through the moon's core and focused on the exact opposite side, the antipodal point, where they ripped the crust apart, creating a complex network of canyons and fractures known as chasmata.

For decades, planetary scientists looked at this battered surface and concluded that Mimas must be frozen solid.

A warm, slushy interior would have relaxed over time, smoothing out the crater walls and erasing the scars.

The fact that the Herschel crater still stands, with walls 5km high and a central peak reaching up to 6km suggests that the ice shell was rigid and immensely thick, supporting these massive structures for billions of years.

Essentially, everything was pointing to Mimas being a geologically dead world.

That is, until scientists found something strange happening on the surface.

In 2010, NASA's Cassini spacecraft swept past MIMIS and turned its composite infrared spectrometer towards the moon to map its surface temperature.

Scientists expected to see a smooth gradient, warmest at the equator where the sun was overhead and fading to cold near the poles.

Instead, they found Pac-Man.

Yes, you heard me correctly.

The thermal map revealed a sharp V-shaped boundary on the moon's leading hemisphere.

Inside the mouth of the shape, the temperatures dropped to an icy minus 196 degrees Celsius, while the surrounding regions were a relatively balmy minus 181 degrees Celsius.

It was a thermal footprint that looked exactly like the 1980s arcade icon eating a dot,

The dot in this case being the Herschel crater.

Even more surprising?