Nasa’s Curiosity rover has detected organic molecules on Mars, including chemicals widely considered building blocks for the origin of life of Earth.

Five of the seven molecules identified in a dried lakebed near the equator had never previously been observed on the red planet. The analysis, performed by the robotic rover, cannot establish whether the organic compounds are linked to potential ancient life on Mars or were delivered by meteorites or formed through geological processes. However, they imply that if microbial life once thrived on Mars, chemical fingerprints should remain there today.

“We think we’re looking at organic matter that’s been preserved on Mars for 3.5bn years,” said Prof Amy Williams, an astrogeologist at the University of Florida and a Curiosity mission scientist, who led the experiment. “Is it life? We can’t tell, based on this information.”

The car-sized Curiosity rover has been wheeling around the Gale crater and Mount Sharp since the robot descended on to the planet in 2012. Surface conditions are harsh, with temperatures dropping to below -100C at night and the lack of an atmosphere meaning Mars is blasted by powerful radiation from the sun. But in the distant past, liquid water flowed on the surface and Mars had an atmosphere that protected it from radiation.

“It had all the conditions for life to start there when life was starting on Earth,” said Prof Andrew Coates, a planetary scientist at University College London’s Mullard Space Science Laboratory, who was not involved in the latest findings. “There’s no known reason why it shouldn’t have started on Mars as well.”

However, scientists have been unsure whether the chemical traces of life from this window of habitability, about 3.7 to 4.1bn years ago, would have survived to the present day.

“For a long time, we thought that all organic matter was going to be seriously degraded by that harsh radiation environment,” said Williams. “It’s really exciting to see [that] large complex material can survive in the subsurface environment.”

The rover recently used its onboard analysis instruments to search for and detect compounds including carbon that are linked to life. The rover identified benzothiophene, a sulphurous chemical often delivered to planets by meteorites. And the experiment hinted at the presence of another nitrogen-bearing organic compound that bears a structure similar to precursors to DNA.

“There are several steps between what we found and DNA,” said Williams. “It is definitely a building block to how DNA is made now. But it is truly just the bricks, not the house. You can generate these molecules geologically.”

“The same stuff that rained down on Mars from meteorites is what rained down on Earth, and it probably provided the building blocks for life as we know it on our planet,” she added.

The findings add to hopes that the European Space Agency’s delayed Rosalind Franklin mission, which is scheduled to launch in 2028, could provide more detailed evidence about the nature of organic chemicals on Mars. The rover will drill to a depth of 2 metres, and will be equipped to perform more sophisticated tests aimed at assessing the origin of such compounds.

The findings are published in the journal Nature Communications.