National Aeronautics and Space Administration (NASA) believes life may have once existed on Mars due to similarities between ancient sedimentary rocks on the Red Planet and Earth, reports Astrobiology magazine.

Curiosity Rover took the images of the sedimentary rocks on Mars while driving through the Gillespie Lake outcrop. Gillespie Lake is a dry lakebed on the planet that experienced seasonal flooding billions of years ago. The Red Planet was a humid and warmer world then, sharing a similar early history with Earth.

Nora Noffke, a geobiologist at Old Dominion University in Virginia, published a paper online last month detailing the surprising morphological similarities between the Gillespie Lake outcrop sedimentary structures (estimated to be 3.7 billion years old) and microbially-induced sedimentary structures (MISS) found in shallow bodies of water and ancient rocks on Earth.

"The fact that she pointed out these structures is a great contribution to the field," Penelope Boston, a geomicrobiologist at the New Mexico Institute of Mining and Technology, told TED. "Along with the recent reports of methane and organics on Mars, her findings add an intriguing piece to the puzzle of a possible history for life on our neighboring planet."

Noffke's report makes a good case for ancient life on Mars, but NASA says it is not definitive proof that the Mars structures were shaped by biology. The only way to know for certain is to bring microbial sediment samples to Earth for scientists to examine under a microscope to see if they have a biological nature.

In her report, Noffke provides a strategy for confirming the possible biological nature of the Mars structures but returning samples to Earth for analyses is not possible yet.

"I don't know if it can be done, but engineers are pretty smart," Chris McKay, an astrobiologist at NASA's Ames Research Center, said. "If you give them a challenge, they usually find a solution. A sample-return mission would be the gold standard, but that's just unlikely to happen anytime soon."

The images which Noffke studied can be seen on NASA's Mars Science Laboratory web page.

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