Nitrogen is a critical element for living organisms on Earth. While atmospheric N2 is plentiful, organisms find it difficult to metabolize, requiring chemical modifications that are rare or absent in abiotic chemistry. Living organisms reduce N2 to NH3 with elaborate, energy-intensive, biochemical processing to create nitrogen-bearing carbon compounds essential for life. Astrobiologists have long discussed what role nitrogen could play in shaping life on other planets. Work on Martian meteorites has provided new insights into nitrogen cycling on Mars. Research on meteorites ties into investigations by NASA's Mars Science Laboratory that are providing on-the-ground information to piece together a more cohesive picture of the importance of nitrogen for establishing a habitable environment.