A new study finds evidence of an ancient ocean on Mars

A retired York University professor has helped unearth new evidence that an ancient ocean once covered about a third of Mars.  

Professor Emeritus Bill Mahaney is part of an international group of scientists that analyzed data from the Gamma Ray Spectrometer (GRS) aboard NASA’s Mars Odyssey orbiter. The spectrometer has the unique ability to detect elements as much as a third of a meter below Mars’ surface. The Mars Odyssey spacecraft was launched on April 7, 2001, and arrived at the red planet on Oct. 24 that year. It has been orbiting Mars ever since.

Right: Mars as seen by the Hubble Telescope in 2001. Image by NASA and the Hubble Heritage team (STScI/AURA).

The data showed areas of enriched potassium, thorium and iron, which scientists believe mark the shorelines of two ancient oceans that existed at different stages of the planet’s evolution. The younger shoreline, on the northern plains of Mars, is estimated to have been about 10 times the size of the Mediterranean, and existed a few billion years ago. The larger, more ancient shoreline encompassed an ocean 20 times the size of the Mediterranean, researchers estimate.

"Results from Mars Odyssey and other spacecraft suggest that past watery conditions likely leached, transported and concentrated these elements," says University of Arizona planetary geologist James Dohm, who led the investigation.

Mahaney, who taught physical geography at York, focused on geochemical analysis, looking for signs of weathering of rocks and minerals, and the presence of paleosols – ancient soils that provide insight into the climate of the early Martian environment. 

"The concept of oceans on Mars has been controversial, so this is very exciting," Mahaney says. "We believe this data provides significant insight into the atmosphere-surface interactions during the early evolutionary stages of the Red Planet."

Prof. Bill MahaneyRight: Bill Mahaney

Scientific debate on the existence of ancient Martian oceans was sparked by several studies going back almost 20 years. One such study hypothesized that erupting magma unleashed massive flooding, which pooled in the northern lowlands of Mars, forming seas and lakes that triggered relatively warmer and wetter conditions, lasting tens of thousands – or perhaps even millions – of years. 

Scientists are driven to understand how and when water existed on Mars in order to further their understanding of whether the planet’s environment has been favourable for microbial life.

"The GRS data highlights the presence of large concentrations of iron, a necessary prerequisite for microbe respiration and evolution," Mahaney says.

Dohm notes the Mars oceans controversy is far from over. "The debate is likely to continue well into the future, perhaps even when scientists can finally walk the Martian surface with instruments in hand, with a network of smarter space-borne, airborne and ground-based robotic systems in their midst." 

Left: The Mars Odyssey spacecraft. Image courtesy NASA.

The findings will be published in a special edition of Planetary and Space Science.

Co-authors include scientists from Italy, Spain and South Korea, along with Canada and the US. Mahaney is the sole Canadian contributor.