Poikilolaimus oxycercus is a microscopic nematode, or roundworm, found alive and well more than a mile below the surface in South Africa, where its ancestors had lived for hundreds or thousands of years. (Gaetan Borgonie)

When scientists speculate about possible life on Mars, they generally speak of microbial or other simple creatures living deep below the irradiated and desiccated surface.  While Mars long ago had a substantial period that was wetter and warmer when it also had a far more protective atmosphere,  the surface now is considered to be lethal.

But the suggestion that some potential early Martian life could have migrated into the more protected depths is often discussed as a plausible, if at this point untestable possibility.  In this scenario, some of that primitive subsurface life might even have survived the eons in their buried, and protected, environments.

This thinking has gotten some support in the past decade with the discovery of bacteria and nematodes (roundworms) found as far down as three miles below the surface of South Africa, in water dated as being many thousands or millions years old.  The lifeforms have been discovered by a team that has regularly gone down into the nation’s super-hot gold and platinum mines to search for life coming out of boreholes in the rock face of deep mine tunnels.

Borgonie setting up a water collector for a borehole at the Driefontein mine in the Witwatersrand Basin  of South Africa.  He said he stopped counting his journeys into the deep mines at 50, but that the number now is much higher. (Courtesy of Borgonie)

Now a  new paper describes not only the discovery of additional deep subsurface life, but also tries to explain how the distant ancestors of the worms and bacteria and algae might have gotten there. 

Their conclusion:  many were pulled down when fractures opened in the aftermath of earthquakes and other seismic events.  While many lifeforms were swept down, only a small percentage were able to adapt, evolve and thus survive.

The is how Gaetan Borgonie, lead author of the paper in Scientific Reports, explained it to me via email:

“After the discovery of multicellular animals in the deep subsurface up to 3.8 km (2.5 miles) in South Africa everyone was baffled and asked the question how did they get that deep? This question more or less haunted us for more than a decade as we were unable to get our head around it.… Read more