Seems to increase the likelihood that Mars has life underground, because Mars rock have gotten here as a meteorite, and some from Earth may have fallen there.

The scientists have been trying to find a lower limit beyond which life cannot exist, but the deeper they dig the more life they find. There is a temperature maximum – currently 122C – but the researchers believe this record will be broken if they keep exploring and developing more sophisticated instruments.

Mysteries remain, including whether life colonises up from the depths or down from the surface, how the microbes interact with chemical processes, and what this might reveal about how life and the Earth co-evolved.

The scientists say some findings enter the realm of philosophy and exobiology – the study of extraterrestrial life.

Robert Hazen, a mineralogist at the Carnegie Institution for Science, said: “We must ask ourselves: if life on Earth can be this different from what experience has led us to expect, then what strangeness might await as we probe for life on other worlds?”

I worked in a microbiology lab for some time, and still lament giving up my beloved microscope now and then... it's an absolutely awe inspiring field. I get microbes. Probably better than most humans. Yet, it excites me to know we still have so very much to learn.