"They reveal Nitrogen compounds on the surface of the planet Mars"

The latest data from NASA's Curiosity rover reveal, for the first time, nitrogen compounds on the surface of Mars. This discovery brings new tracks of that the planet red could have hosted life in some moment of their history before return is dry and sterile.

Previously identified nitrogen compounds in the atmosphere of Mars, but never before found nitrates on the surface, but now with this finding was found in both surface dust samples and sediments Gale Crater.

Fig. 1. Sedimentary rocks of the Gale crater (Grotzinger et al., 2014).

Nitrogen in the form of N2 makes up approximately 2% of the Martian atmosphere, is now shown that the concentration of nitrogen in the surface of Mars is of 20-250 nanomoles in the form of nitric oxide or nitrogen monoxide, but little is known about other potential reservoirs of N on Mars, including those which may contain fixed forms of N (i.e. NH₃, NH₄⁺ and NO₃⁻) in the mantle, crust and sediments.

There is a concentration of nitrogen in the surface of Mars, it suggests that "the existence of a source of biochemically accessible nitrogen on Mars seems a fundamental prerequisite for the possible habitability of the planet", an example of this is the terrestrial life that requires a form fixed nitrogen for incorporation in biomolecules as nucleobases and amino acids that are the building blocks for DNA, RNA and proteins

Thus the presence of N fixed on Mars suggests that, at some point, was established the first half of the nitrogen cycle. On Earth, the N in your cycle returns to the atmosphere by denitrification by biological activity, but on Mars, the likely absence of life near the surface would result in fixed N accumulated as nitrate in the geological surface of Mars.

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http://www.pnas.org/content/early/2015/03/18/1420932112.full.pdf?sid=f4b9cfe9-fd7e-434d-badc-095f6362fd1a