Nitrogen, Earth’s biosphereThe study, published in Nature Communications on Jan. 22 , focuses on a type of metabolism called nitrogen fixation, or diazotrophy. On Earth, there is a select group of organisms called diazotrophs that can perform nitrogen fixation. This means that the N-isotope signatures left behind by ancient nitrogenase enzymes could be different than the ones we see today. “If we want to recognize life beyond Earth, we can’t limit ourselves to life as we know it today,” said Kaçar. Nitrogenase, search for lifeNow that scientists have validated the use of N-isotopes as a biosignature for ancient life on Earth, the same technique could potentially be used on other rocky worlds.