NASA may have finally found direct evidence for life on Mars.
Critical 'spikes' in methane gas - an organic chemical thought to be a key sign of life - have been recorded by a laser measuring device attached to the $2 billion Curiosity rover.
It revealed a low background level of methane which 'spiked' 10-fold over a period of just 60 Martian days.
NASA thinks the discovery could point to the existence of life on the red planet.
READ MORE: Life on Mars: What do we know?
Low levels of background methane are known to be present on Mars, but there are several long-term processes that can explain its presence.
Spikes are more significant in the search for life, because organic life is one of the few known causes for such a sudden shift.
In four sequential measurements, Curiosity showed the methane level soaring from about 0.69 parts per billion by volume (ppbv) to 7.2 ppbv.
The spikes occurred within 200 to 300 metres of each other and less than a kilometre from where the lower readings were detected.
In a paper published in the journal Science, the team led by Dr Chris Webster, from Nasa's Jet Propulsion Laboratory, suggest that while there are several possible causes for the readings, the most legitimate explanation at present is the existence of organic life.
The authors argue that the readings could have originated from microbial bugs known as methanogens, a known source for methane gas.
This follows the discovery of an ancient freshwater lake in the same crater earlier this year and -- scientists believe -- further strengthens the case for their being life on Mars.
Another major discovery by Curiosity was that of water being found in the fine-grained soil within the crater. Each cubic foot of Martian soil was found to contain around two pints of water, not freely accessible but attached to minerals.
ExoMars, a European Space Agency mission, will land in the same area in 2019. It's hoped that ExoMars will be able to further corroborate Curiosity's findings by using specially designed equipment which can detect the biomarkers of life.