Context:

• Curiosity rover has detected a bonanza of organic compounds on the surface of Mars and seasonal fluctuations of atmospheric methane. The findings released, mark some of the strongest evidence ever that Earth’s neighbour may have harbored life.

Gale crater:

• NASA scientists emphasized there could be nonbiological explanations for both discoveries made by the Curiosity rover at a site called Gale crater, leaving the issue of Martian life a tantalizing but unanswered question.
• Three different types of organic molecules were discovered when the rover dug just 5 cm into roughly 3.5 billion-year-old mudstone, a fine-grained sedimentary rock, at Gale crater, apparently the site of a large lake when ancient Mars was warmer and wetter than the desolate planet it is today.
• Curiosity also measured an unexpectedly large seasonal cycle in the low levels of atmospheric methane.
• About 95 % of the methane in Earth’s atmosphere is produced from biological activity, though the scientists said it is too soon to know if the Martian methane also is related to life.
• Organic molecules are the building blocks of life, though they can also be produced by chemical reactions unrelated to life.
• The scientists said it is premature to know whether or not the compounds were created in biological processes.
• Whether anywhere other than Earth has harbored life, perhaps even in microbial form, is one of the paramount questions in science.

Other sources of organic material

• There’s three possible sources for the organic material.
• “The first one would be life, which we don’t know about.
• The second would be meteorites.
• And the last one is geological processes, meaning the rock-forming processes themselves.”

Seasonal variations

• The amount of methane peaked at the end of summer in the northern hemisphere at about 2.7 times the level of the lowest seasonal amount.
• The scientists were surprised to find organic compounds, especially in the amounts detected, considering the harsh conditions, including bombardment of solar radiation on the Martian surface.
• After drilling, Curiosity heats the rock samples, releasing the compounds. Referring to the findings regarding organic compounds and methane, 
• The scientists hope to find better preserved organic compounds with Curiosity or other rovers that would allow them to check for chemical signatures of life.

Source:TH