The news already leaked out and last night NASA confirmed it: a group of researchers who were conducting tests in Mono Lake, a California lake with a harsh environment, found a microorganism capable of thriving in an environment full of arsenic.

In the past microbes capable of surviving elevated concentrations of arsenic were found but the one discovered during this NASA-founded research goes beyond because it can use arsenic in its biochemistry.

Earth living creatures use six base elements to build the molecules needed for life: carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur. The microbe just discovered, the GFAJ-1 strain that belongs to a common group of bacteria called the Gammaproteobacteria, can use arsenic instead of phosphorus in its DNA, in proteins and cell membranes.

The existance of life forms that use arsenic was part of the theories about alternative biochemistries, finding on the Earth a bacterium that can actually do it is a big discovery because it enables experimental researches that can shed more light on the evolutionary mechanisms of living creatures.

Imagining the possible biochemistry of life forms on other planets is hard, being able to observe bacteria that can live in environments which are in theory poisonous helps to broaden perspectives concerning extraterrestrial life. One of the most complex problems in deciding on which planets to look for life forms is to pick an environment where life can be possible: knowing that there are at least interesting chances that living creatures can thrive in a certain environment could help us to understand where to search.

When the first rumors about NASA announcement reached media there were people expecting that an actual extraterrestrial life form was found: the GFAJ-1 is alien because of its biochemistry and it’s an important discovery for science, for me that’s enough.