An area of the planet's northern plains called Acidalia Planita contains thousands of the circular mounds, formed from ancient sediment that might contain evidence of possible past or present life, Astrobiology magazine reports.
"If there was life on Mars, it probably developed in a fluid-rich environment," Dorothy Oehler of the Astromaterials Research and Exploration Science Directorate at NASA's Johnson Space Center said.
"Mud volcanoes themselves are an indicator of a fluid-rich subsurface, and they bring up material from relatively deep parts of the subsurface that we might not have a chance to see otherwise," she said.
She and her colleagues estimate there may be as many as 40,000 mud volcanoes in the Acidalia region.
Scientists first observed the mounds in Acidalia using imagery obtained from the Viking mission in the late 1970s.
U.S. researcher Kenneth Tanaka was one of the first to suggest they were mud volcanoes.
"I also thought that these features, which also occur elsewhere in the northern plains of Mars, were good places to search for signs of life," Tanaka, a scientist at the Astrogeology Science Center of the U.S. Geological Survey, said.