NASA’s rover Curiosity has found organic compounds on Mars, the first definitive proof of materials on the Red Planet that, on Earth, are building blocks for life.

“We have had a major discovery. We have found organics on Mars,” Curiosity lead scientist John Grotzinger, with the California Institute of Technology in Pasadena, Calif., said during a webcast press conference at the American Geophysical Union conference in San Francisco.

Whether the organics were delivered by carbon-rich meteorites or formed on Mars has yet to be determined.

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The discovery, paired with a sister investigation that found occasional spikes of methane gas in the Martian atmosphere, is a turning point for the mission, which began 2.5 years ago inside a 96-mile wide impact basin named Gale Crater.

On Earth, more than 90 percent of the atmospheric methane is produced by biological processes. The rest is tied to geochemical processes.

Mars missions used to be ones "where you observe and seek to explain, what I like to call the ‘Star Trek’ mode -- build a spacecraft, go out there, find cool things that nobody saw before. Mars is now becoming a proving ground for a much more deductive line of science," Grotzinger said.

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Explaining both the organics and the methane will require far more analysis, much of which may be beyond the rover’s capabilities. Both materials on Earth are tied to life, which may or may not prove to be true on Mars as well.

“We just have to respect that it is a possibility,” Grotzinger said.

Curiosity got a taste of organics two years ago when it analyzed samples drilled out from an ancient mudstone called Cumberland, but scientists couldn’t rule out until now that the carbon-containing compounds were hitchhikers from Earth.

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“It’s not trivial to generate data like this in a laboratory, let alone on another planet,” Curiosity participating scientist Roger Summons, with Massachusetts Institute of Technology, told reporters.

Organics, whether delivered by comets and asteroids crashing onto the surface or produced indigenously, face a tough life on Mars. The planet is constantly bombarded by cosmic rays, which destroy organics. Surface soils are strongly oxidizing, which break down molecular bonds. Perchlorates also produce chlorine, which change the molecules.

Curiosity scientists are mulling options to mitigate the effects of perchlorates in an effort to find not only more organics, but more complex molecules as well.