It seems that Mercury is the ugly duck in the Solar System. Its surface looks like a face with many large scars, Moon-like highlands, mountains, plains, slopes, and valleys. For off-road and winter sports lovers, it would be Paradise. But, the 430 degrees Celsius on the dayside and -180 degrees Celsius on the nightside, together with the lack of atmosphere, make Mercury an impossible environment for any kind of life.
The closest planet to the Sun has remained the least known of all the planets that form the Solar System — Mostly because Mercury couldn’t have hosted life, or at least conditions for it, so there was no point in getting to know it. But, surprisingly enough, Mercury has proven to have ever-lasting ice on the dark side of it, the one that can never see the Sun. And new theories sustain the idea that it once hosted more of the volatiles necessary for habitability than water.
Over the years, astronomers tried to find an explanation for the bumpy geological structure of Mercury. Until 2018, the hypothetical Late Heavy Bombardment was one of them. Now questioned, the Late Heavy Bombardment was believed to have happened approximately 4.1 to 3.8 billion years ago. Scientists presumed that a tremendous number of asteroids collided with Mercury, Venus, Earth, and Mars, bringing new substances to them, such as ice.
Alien life on Mercury might have existed once
But, like many theories that scientists imagine possible to explain the things they bump into when searching the Universe, this one doesn’t seem so likely anymore. It might be that asteroids brought things with them when they collided and left it there to change things, but it can’t be the explanation for all of it.
What’s more, the surface of Mercury continued to deflate for another two billion years after the so-called bombardment. So, it couldn’t be a comprehensive explanation, even if it was true.
So, new theories are explored. For instance, one of them says that Mercury had hidden under its surface volatiles that were expelled from the interior and transformed into gases (like the volatiles they were!) by the heat and magmatic activity. Emptying the interior of the planet from large quantities of substances, the planet deflated like a balloon.
So, today we might believe there was water underneath Mercury’s surface. Still, Paul Hayne, a planetary scientist at the University of Colorado Boulder, wisely advises: “you could have transient pockets of high-water activity. But I don’t think this is a case where we’d see massive pools of water and subsurface lakes and that sort of thing.”