Mars has been volcanically active throughout its past up to modern times, Baker said. Eruptions and other volcanic activity "release iron and sulfur dioxide that can produce these types of acidic conditions," he said.
Baker and his colleagues say they've only spawned the beginning of an idea that will hopefully lead scientists to a fuller understanding of the red planet's past.
The new study suggests what is physically reasonable. But it does not attempt to test the theory through the long history of Mars. Scrutiny of such a vast geologic record has yet to be attempted.
"Our feeling is that, like all science, this may not be the absolute correct answer. But it can stimulate work that can get us there," Baker said. "It's consistent with the data [and implies] that we're at least following the right path."
The theory lends its controversial weight to gathering evidence that suggests ancient oceans existed on Mars. Oceans are considered a key criteria for past life on Mars.
NASA's Mars exploration rover Opportunity has identified perhaps the best evidence for water on the red planet from its landing zone in the Meridiani Planum, a flat area near the equator.
Rocks on that plain yielded clues of texture, mineral composition, and chemistry that strongly suggest that the geologic matter was deposited in flowing, salty water.
"The plains themselves extend over an area about the size of Oklahoma," said Joy Crisp, a Mars Exploration Rover Mission scientist at NASA's Jet Propulsion Laboratory in Pasadena, California.
"We have seen roughly 30 feet [10 meters] of thickness of these [deposited] layers, laid down one after the other," she said. "So we're getting a sense that this body of water was around for some time."
Data collected in orbit suggest the sediment stack was some 1,650 feet (500 meters) thick and covered an area the size of Northern Europe's Baltic Sea.
Had it existed, might such a vast, ancient sea once have teemed with life? No one knows for sure. But the authors of the new study suggest that the acidic nature of the Martian ocean they say existed might have been suitable for life.
Writing in their study, the researchers stated: "In fact, if biological inhabitation of early Mars is considered plausible, moderate acidic oceans represent the closest terrestrial analogue for a biogenic environment, similar to that where life originated on Earth."
Don't Miss a Discovery
Sign up for the free Inside National Geographic newsletter. Every two weeks we'll send you our top news stories by e-mail.
For more Mars stories, scroll to bottom.
SOURCES AND RELATED WEB SITES