NASA rover data shows Mars had the ingredients needed for life

WASHINGTON, June 7 (Reuters) - A NASA rover has detected a bonanza of organic compounds on the surface of Mars and seasonal fluctuations of atmospheric methane in findings released on Thursday that mark some of the strongest evidence ever that Earth's neighbor may have harbored life.

But National Aeronautics and Space Administration 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 2 inches (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 percent 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.

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Portions of the Martian surface shot by NASA's Mars Reconnaissance Orbiter show many channels from 1 meter to 10 meters wide on a scarp in the Hellas impact basin, in this photograph taken January 14, 2011 and released by NASA March 9, 2011. Scientists have found the first evidence that briny water may flow on the surface of Mars during the planet's summer months, a paper published on Monday showed. Researchers found telltale fingerprints of salts that form only in the presence of water in narrow channels cut into cliff walls throughout the planet's equatorial region. REUTERS/NASA/JPL-Caltech/Univ. of Arizona/Handout FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. IT IS DISTRIBUTED, EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS
Dark, narrow, 100 meter-long streaks on Mars inferred to have been formed by contemporary flowing water are seen in an image produced by NASA, the Jet Propulsion Laboratory (JPL) and the University of Arizona. Scientists have found the first evidence that briny water may flow on the surface of Mars during the planet's summer months, a paper published on Monday showed. NASA/JPL/University of Arizona/Handout THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. IT IS DISTRIBUTED, EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS. FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS
Dark narrow streaks called recurring slope lineae emanating out of the walls of Garni crater on Mars are seen in an image produced by NASA, Jet Propulsion Laboratory (JPL) and the University of Arizona. Scientists have found the first evidence that briny water may flow on the surface of Mars during the planet's summer months, a paper published on Monday showed. NASA/JPL/University of Arizona/Handout THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. IT IS DISTRIBUTED, EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS. FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS
A circular depression on the surface of Mars is pictured in his image acquired on Jan. 5, 2015 by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter (MRO), provided by NASA. The spacecraft has been orbiting Mars since March 2006 and completed its 40,000th orbit around Mars on Feb. 7, 2015. REUTERS/NASA/JPL-Caltech/University of Arizona/Handout
NASA's Mars rover Curiosity's hole drilled into a rock target, "Cumberland," on Mars on May 19, 2013 is shown in this NASA photo. NASA?s Mars rover Curiosity has found carbon-containing compounds in samples drilled out of an ancient rock, the first definitive detection of organics on the surface of Earth?s neighbor planet, scientists said on Tuesday. REUTERS/NASA/Handout (OUTER SPACE - Tags: SCIENCE TECHNOLOGY) FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. IT IS DISTRIBUTED, EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS
NASA's Mars Exploration Rover Opportunity is shown in this handout photo released to Reuters July 29, 2014. Opportunity has set a new off-Earth, off-road distance record, logging just over 25 miles (40 km) on the surface of the Red Planet to surpass the old benchmark set in 1973 by a Russian probe on the moon. REUTERS/NASA/JPL-Caltech/Cornell Univ./Arizona State University/Handout (UNITED STATES - Tags: SCIENCE TECHNOLOGY) FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. IT IS DISTRIBUTED, EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS
This image from the right Mast Camera (Mastcam) of NASA's Curiosity Mars rover shows rough spherical features on the surface of the planet in an area called 'Yellowknife Bay' in this NASA handout released January 15, 2013. These features are interpreted as concretions, implying they formed in water that percolated through pores in the sediment. Spherical concretions have previously been discovered in other rocks on Mars. REUTERS/NASA/JPL-Caltech/MSSS/Handout (OUTERSPACE - Tags: SCIENCE TECHNOLOGY ENVIRONMENT) FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. IT IS DISTRIBUTED, EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS
An image from the Mast Camera (Mastcam) on NASA's Mars rover Curiosity shows the surface of the planet with inclined layering known as cross-bedding in an outcrop called "Shaler" on a scale of a few tenths of a meter, or decimeters (1 decimeter is nearly 4 inches) in this NASA handout released January 15, 2013. REUTERS/NASA/JPL-Caltech/MSSS/Handout (OUTERSPACE - Tags: SCIENCE TECHNOLOGY ENVIRONMENT) FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. IT IS DISTRIBUTED, EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS
The surface of the planet Mars inside Gale's Crater is shown as NASA's Mars rover Curiosity drives toward a flat rock with pale veins that may hold clues to a wet history on the planet in this NASA handout photo released January 15, 2013. If the rock meets rover engineers' approval when Curiosity rolls up to it in coming days, it will become the first to be drilled for a sample during the Mars Science Laboratory mission. REUTERS/NASA/Handout (OUTERSPACE - Tags: SCIENCE TECHNOLOGY ENVIRONMENT) FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. IT IS DISTRIBUTED, EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS
NASA's Mars Science Laboratory rover Curiosity appears as a bluish dot near the lower right corner of this enhanced-color view from the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter taken on June 27, 2013 and released on July 24, 2013. The rover's tracks are visible extending from the landing site, "Bradbury Landing," in the left half of the scene. Two bright, relatively blue spots surrounded by darker patches are where the Mars Science Laboratory spacecraft's landing jets cleared away reddish surface dust at the landing site. REUTERS/NASA/JPL-Caltech/Univ. of Arizona/Handout via Reuters (OUTER SPACE - Tags: ENVIRONMENT SCIENCE TECHNOLOGY) ATTENTION EDITORS - THIS IMAGE WAS PROVIDED BY A THIRD PARTY. FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. THIS PICTURE IS DISTRIBUTED EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS
A rock outcrop called Link pops out from a Martian surface in this NASA handout image taken by the 100-millimeter Mast Camera on NASA's Curiosity Mars rover September 2, 2012 and released September 27, 2012. Rounded gravel fragments, or clasts, up to a couple inches (few centimeters) in size are in a matrix of white material. The outcrop characteristics are consistent with a sedimentary conglomerate, or a rock that was formed by the deposition of water and is composed of many smaller rounded rocks cemented together. Scientists enhanced the color in this version to show the Martian scene as it would appear under the lighting conditions we have on Earth, which helps in analyzing the terrain. REUTERS/NASA/JPL-Caltech/MSSS/Handout (UNITED STATES - Tags: SCIENCE TECHNOLOGY) THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. IT IS DISTRIBUTED, EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS. FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS
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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.

"There's three possible sources for the organic material," said astrobiologist Jennifer Eigenbrode of NASA's Goddard Space Flight Center in Maryland. "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."

The rover, which has allowed scientists to explore whether Mars ever boasted conditions conducive to life, in 2014 made the first definitive detection of organic molecules, also in Gale crater rock formed from ancient lake sediment - but it was a much more limited set of compounds.

"What the organic detections in the rock do is to add to the story of habitability. It tells us that this ancient environment on Mars could have supported life," Eigenbrode said. "Everything that was needed to support life was there. But it doesn't tell us that life was there."

Christopher Webster, an atmospheric science research fellow at NASA's Jet Propulsion Laboratory in California, said it is possible existing microbes are contributing to the Martian atmospheric methane.

"With this new data, we again cannot rule out microbial activity as a potential source," Webster said.

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, Webster said, "They hint at an earlier time on Mars when water was present and the existence of primitive life forms was possible."

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.

The research was published in the journal Science. (Reporting by Will Dunham; editing by Jonathan Oatis)

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