The list of places in our solar system that might be home to extraterrestrial life just keeps getting longer. There are moons around Saturn and Jupiter that may be the most likely place to find alien life and it's recently become more possible that Mars might have life below its surface, too. Some scientists have even put forth Earth's evil-twin Venus as potentially having alien life. And now Mercury, the closest planet to the sun, has also been put forward as a potential, although very unlikely, home for extraterrestrial life.
A new paper published in the journal Scientific Reports lays out the case for life on Mercury. While the planet's small size and close proximity to the sun results in no real atmosphere and a surface temperature hot enough to melt lead, the new paper's authors believe that if life were to exist on Mercury it would be underground. The clue to potential sub-surface life lies in Mercury's distinctive "chaotic terrain." Speaking to the New York Times, co-author of the paper Dr. Deborah Domingue, of the Planetary Science Institute in Tucson, Arizona, says:
“Think of a kid throwing up a bunch of building blocks and how they land. Some are up, some are down, some are tilted — that’s chaotic terrain.”
For almost 50 years, Mercury's chaotic terrain has been blamed on earthquakes resulting from a massive meteor impact. The new paper challenges that explanation, arguing that the chaotic terrain was created some two billion years the meteor impact.
The researchers, led by Dr. Alexis Rodriguez, also found that there are areas of the chaotic terrain that appear sunken, as if layers of the terrain have simply vanished. The most likely explanation is the presence of subsurface volatiles, chemicals that can easily change between solids liquids and gasses. The researchers postulate that an intrusion of magma from Mercury's core heated these volatiles, turned them rapidly into gasses and knocked the supports out from the chaotic terrain. These volatiles are also where the possibility of life comes into play. One of the most well known of possible subsurface volatiles is water.
If there's one thing everyone knows about Mercury, it's that the planet is extremely hot. The surface temperature can reach 800 degrees Fahrenheit during the day. Due to the lack of atmosphere, night time on Mercury can drop to negative 290 degrees Fahrenheit. Neither day or night on the surface of Mercury is conducive to liquid water, let alone life, but if it exists it wouldn't be on the surface but below it.
Only a short distance below the surface, the temperatures on Mercury become much more reasonable. Not for us, of course. It's still hot enough to cook us alive. But we've found microbes in deep-sea vents Earth that thrive in hotter-than-boiling water. If there were pockets of pockets of water below the surface of Mercury, it may be an ideal environment for some types of life. Co-author of the study Jeffrey Kargel says:
“It is possible that as long as there was water, the temperatures would be appropriate for the survival and possibly the origin of life.”
I thought Alexis had lost it at some point. But the more I dug into the geologic evidence and the more I thought about the chemistry and physical conditions there, the more I realized that this idea — well it might be nuts, but it’s not completely nuts.”
Researchers say there's little to no possibility of underground oceans, lakes, or anything of that nature on Mercury. Any subsurface water would be bound to rocks in small clusters. Any life that would be under the surface of Mercury would be very basic, microbial lifeforms, and even that is an outside possibility. But still, it's beginning to seem like habitable environments, of some sort, in our solar system may be the norm, rather than the exception.