An expert on geobiology argues that she’s found evidence that microbes once lived on Mars using one of the photos from NASA’s Curiosity rover.

Researchers have already found evidence of organic chemistry in rock formations, evidence of water on the Red Planet, and methane in the atmosphere, but no direct proof that microscopic organisms once lived on the planet, according to the Christian Science Monitor.

However, in a paper that examines rock structures on Mars photographed by the Curiosity rover, Old Dominion University geomicrobiologist Nora Noffke said the structures on one particular rock look very similar to those that were created by microbes back on Earth. Noffke has studied microbially induced sedimentary structures (MISS) for 20 years, and recently reported on a 3.48-billion-year-old MISS formation in Australia, which would still be slightly younger than the rock in question on Mars at 3.7 billion years old, scientists believe.

It’s not proof of ancient life on Mars — that would require bringing the rock back to Earth and examining it more closely, something that won’t happen until NASA is able to send a manned mission to the planet. But it does provide intriguing circumstantial evidence that further bolsters the case for visiting the Red Planet.

NASA planetary scientist Chris McKay of the Ames Research Center said many times when people say something on Earth looks like something on Mars, it’s not very convincing, but Noffke has presented a very carefully done analysis that represents the first of its kind to be published in the journal he edits, called Astrobiology.

Mars may be a rough and inhospitable climate today, but it shared a similar history with the Earth. It was likely much warmer with more moisture billions of years ago, as evidenced by the rock formations on the planet. The rock in question was found in the Gillespie Lake, which is a part of a dry lakebed on Mars. The lake is believed to have had seasonal flooding, which would have been the perfect environment for microbes.

Microbes on Earth typically live in colonies that form “mats” that can trap and rearrange sediments. It creates a unique structure that can be found across the Earth, and feature hallmarks such as pockets, domes, pits, cracks, and erosional remnants.

Noffke acknowledged that further evidence would be needed to verify the hypothesis she had put forward. In order to get it, it will require samples, which is not technically feasible at this stage in research of Mars. However, with future efforts planned such as the Mars 2020 rover mission and an eventual manned mission to the planet, there are likely to be opportunities to do that at some point in the future.