NASA has claimed that its Curiosity rover is unlikely to have found evidence of microbial life on Mars.

Last week geobiologist Dr. Nora Noffke claimed that images taken by the Martian rover contained evidence of past life. Noffke is not officially associated with the Curiosity project, but released a paper detailing her analysis of images of the Gillespie Lake, which is located in the Gale Crater.

NASA Says Curiosity Rover Unlikely To Have Found Microbe Traces

Curiosity Rover unlikely to find life on Mars: Differing opinions

She claimed that there were similarities between “microbially induced sedimentary structures” (MISS) found on Earth, and structures that she noticed in photos of the Gillespie Lake. Noffke was careful to stress that she did not think that the structures were definitive proof of past life on Mars, and was simply hypothesizing that they could be consistent with a biological origin.

According to mission project scientist Ashwin Vasavada, from NASA’s Jet Propulsion Laboratory in Pasadena, California, the Curiosity team also noticed the structures but came to a different conclusion.

“We really didn’t see anything that can’t be explained by natural processes of transporting that sand in water, and the nature of the rocks suggested that it was just a fluvial sandstone,” he said.

Although he did not agree with Noffke’s hypothesis, Vasavada was keen to encourage the involvement of outside researchers.

Further analysis possible

If the team wanted to carry out further analysis of the site they have a variety of ways of doing so, including taking close-up images using Curiosity’s Mars Hand Lens Imager, or taking a rock sample for analysis in the Sample Analysis at Mars (SAM) instrument.

One such sample was taken from the fine-grained mudstone known as Sheepbed, found beneath Gillespie Lake, which is part of an area known as Yellowknife Bay. Analysis of the rock, as well as other observations, led the team to conclude that the area could have supported microbial life in the past.

Organics were also detected, the first time that definitive proof of the existence of life’s building blocks had been found on the Red Planet.

Curiosity landed on Mars in August 2012, and spent just under a year in the Yellowknife Bay area, before leaving for a 5,500 meter peak known as Mount Sharp in July 2013. Scientists aim to piece together a history of Martian environmental conditions by analyzing the rocks found at different altitudes on the mountain.