To answer that question, the researchers took samples from different sections of the crater to see if there was a relationship between the level of impact and the colonization of microorganisms within the rock samples. They classified the rocks near the center of the crater as extremely damaged by the impact, and rocks farthest from the center as unaffected by the event. When a meteorite crashes, the energy liberated by the event is so great, the rocks which it hits are metamorphosed—completely changed.

These rocks’ minerals are altered due to high pressure shock waves generated by the impact. The more shock a rock suffers, the more transformed and fractured it will be, and as a result, there will be more empty space inside the rocks. Along with this increased porosity, minerals in the rocks are deformed due to the intense pressure. Some grains are turned to glass, which is translucent, helping sunlight penetrate deeper into the rock. This produces a better environment for photosynthetic microbial growth.

Microorganisms such as cyanobacteria were found in all the samples of the study site. As expected, the study showed that the amount of metamorphism the crater’s rocks experienced led to different ranges of microbial diversity.

The counterintuitive result, however, is that rocks which experienced a high shock pressure from the impact were found to have more microbial diversity than other samples that were barely affected by the event, because of the direct relationship between the impact damage and the porosity of the rock. With more empty space, microorganisms can better colonize rocks, and extract nutrients from them more easily.

These results could be useful in the search for life on Mars, given the extraordinary number of craters there. Low temperatures and extremely low water availability govern the surface of the planet, but impact craters could provide a sheltered habitat. If life survived the most chaotic, dramatic and apocalyptic phases of Earth’s geologic history, it would not be surprising if there is, in fact, something living inside a Martian crater.