NASA's Mars Curiosity rover measured a 10-fold spike in methane, and researchers are working to solve the mystery of what caused it.

Curiosity's onboard Sample Analysis at Mars (SAM) laboratory searched for methane in Mars' atmosphere a dozen times over the course of 20 months. Over a two-month period in late 2013 and early 2014, four measurements revealed methane levels of seven parts per billion, which is about 10 times higher than recording taken before and after that.

"This temporary increase in methane -- sharply up and then back down -- tells us there must be some relatively localized source," said Sushil Atreya of the University of Michigan, Ann Arbor, and Curiosity rover science team. "There are many possible sources, biological or non-biological, such as interaction of water and rock."

The rover also detected other organic molecules in a rock-powder sample from Mars' Cumberland rock, which marks the first surface organics ever conclusively discovered on the Red Planet. The researchers suggest these organics either formed locally on Mars, or were delivered by meteorites.

Organic molecules usually contain carbon and hydrogen, and are known to be the "building blocks of life." While these new findings do not prove the presence of life on the Red Planet, they do suggest that Mars is chemically active and could potentially harbor microbes.

"We will keep working on the puzzles these findings present," said John Grotzinger, Curiosity project scientist of the California Institute of Technology in Pasadena (Caltech). "Can we learn more about the active chemistry causing such fluctuations in the amount of methane in the atmosphere? Can we choose rock targets where identifiable organics have been preserved?"

In the analysis, researchers worked to determine whether the detected organic material was of Martian in origin. The team observed some samples were most likely transported from Earth on the Curiosity rover, but further testing also revealed the presence of local compounds.

"This first confirmation of organic carbon in a rock on Mars holds much promise," said Curiosity participating scientist Roger Summons of the Massachusetts Institute of Technology in Cambridge. "Organics are important because they can tell us about the chemical pathways by which they were formed and preserved. In turn, this is informative about Earth-Mars differences and whether or not particular environments represented by Gale Crater sedimentary rocks were more or less favorable for accumulation of organic materials. The challenge now is to find other rocks on Mount Sharp that might have different and more extensive inventories of organic compounds."

Detections of three-billion-year-old lakebed minerals suggest the planet lost most of its water before the feature even formed, and continued to lose large quantities of water after that. Hydrogen isotopes from water molecules found in the rocks showed the ratio of the heavy isotope deuterium to the most common hydrogen isotope provided a comparison signature for Mars' history.

"It's really interesting that our measurements from Curiosity of gases extracted from ancient rocks can tell us about loss of water from Mars," said Paul Mahaffy, SAM principal investigator of NASA's Goddard Space Flight Center in Greenbelt, Maryland, and lead author of a report published online this week by the journal Science.

The ration of deuterium to hydrogen has changed over the years because the lighter isotope (hydrogen) escapes from the upper atmosphere more quickly, looking at this ration in water both in the current atmosphere and trapped in ancient rocks can show how this ratio has changed throughout history. The Cumberland sample contained about one-half the ratio in water vapor as what can be seen in Mars' atmosphere today. This suggests the planet's water loss took place after the rock was formed.

The findings were published in a recent edition of the journal Science.