Curiosity Rover Finds Ancient ‘Building Blocks for Life’ on Mars – Space.com

NASA’s Curiosity Mars rover took this self-portrait on Jan. 23, 2018, on the slopes of the towering Mount Sharp.
Credit: NASA/JPL-Caltech/MSSS[/caption]NASA’s Mars rover Curiosity has identified a variety of organic molecules, the carbon-based building blocks of life as we know it, in 3.5-billion-year-old Red Planet rocks, one of the papers reports.

“These results do not give us any evidence of life,” stressed study lead author Jennifer Eigenbrode, a scientist at the Solar System Exploration Division at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. [The Search for Life on Mars: A Photo Timeline]

“But there is a possibility that [the organics] are from an ancient life source; we just don’t know,” Eigenbrode told Space.com. “And even if life was never around, they [the molecules] tell us there was at least something around for organisms to eat.”

The other new paper also details a Curiosity find: that methane concentrations in Mars’ atmosphere cycle seasonally. The discovery suggests that this gas, which here on Earth is produced primarily by living organisms, is seeping out from underground reservoirs, study team members said.

Again, these results are not evidence of life — methane can also be produced by geological processes — but they are consistent with the presence of Martian organisms, which is exciting in and of itself.

“We cannot rule out the possibility that it was created biologically,” said study lead author Chris Webster, a senior research fellow at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California. “We can’t say that it was, but we’re certainly not dropping that idea. So, in a sense, that’s positive for the astrobiologists in the world.”

Both new studies were published online today (June 7) in the journal Science.

The building blocks of life
The serious hunt for organics on Mars has a long and complicated history. It starts with NASA’s twin Viking landers, which touched down on different parts of the Red Planet in 1976 to search for signs of life. The Vikings’ science payload included an instrument called a gas chromatograph mass spectrometer (GCMS), which heated Martian soil and studied the molecules that boiled off.

While the Vikings’ life-hunting experiments returned intriguing but ambiguous results, the GCMS found no organics. Indeed, the instrument spotted little of note, save for two chlorinated chemicals — chloromethane and dichloromethane — that were thought to be contaminants from Earth. This result convinced most scientists at the time that Mars is a dead planet; life as we know it is impossible without organic molecules, after all.

But that thinking began to shift a bit in 2008, when NASA’s Phoenix lander found chlorine-containing chemicals called perchlorates in the Martian soil. Some researchers noted that perchlorates can destroy organics in a heated sample, and suggested that such reactions may have been responsible for the Vikings’ null GCMS result.

In 2011, this hypothesis got some experimental backing. In a lab here on Earth, researchers heated perchlorate-spiked soil and spotted chloromethane and dichloromethane boiling out of the sample.

Then, Curiosity came onto the scene. The rover touched down inside Mars’ huge Gale Crater in August 2012, kicking off a quest to determine if the Red Planet has ever been capable of supporting microbial life. Curiosity mission scientists quickly answered that question in the affirmative, finding that Gale hosted a long-lived, potentially habitable lake-and-stream system billions of years ago. [Photos: Ancient Mars Lake Could Have Supported Life]

The rover also found organics in relatively short order, using its Sample Analysis at Mars (SAM) instrument. SAM identified chlorinated hydrocarbons, such as chlorobenzene and dichlorobutane, in powdered samples drilled out of rock at a spot called Yellowknife Bay, which is near Curiosity’s landing site.

The discovery confirmed the existence of native Martian organics. It was tough to know their full story, however, given the seeming ubiquity of perchlorates in the red dirt. For example, did these chlorinated compounds exist as-is in the rock, or were they created from other indigenous organics in a reaction inside SAM, which also heats its samples?

“We were a bit puzzled; we weren’t sure what those molecules really meant in the bigger picture of the search for life,” Eigenbrode said. “But it gave us a lot of anticipation that, if we can find these molecules here, perhaps we’re going to come across other layers of rock that have more organics in them. And that’s exactly what happened.”

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