Instead, in the regions on Mars where rivers might have flowed, there are few of the telltale erosion features seen on Earth, said Stepinski. That means, he said, that the Red Planet might never have had long-lived wet climate.
But instead of leaving the matter as simply an observation, Stepinski and colleague S. Coradetti of MIT created a mathematical approach that renders elevation data of 26 alleged Martian watersheds into mathematical "functions." The researchers then applied the same approach to 27 earthbound watersheds.
Finally, Stepinski and Coradetti used a neural network technique to let the watersheds of both planets group themselves by their similarities. The result was a chart in which most Mars watersheds and Earth watersheds segregated into distinct groups. The work is featured in the latest issue of Geophysical Research Letters.
"This has allowed me to go from just an observation to a general statement" about Earth and Mars water-formed landscapes, said Stepinski. "Absolutely, there is a difference."
Earth landscapes are overwhelmingly carved by water. On Mars, on the other hand, "maybe there was rain," said Stepinski, "but it wasn't the dominant shaper of the landscape."
"Work such as this is very valuable since it introduces numerical rigor to some of the more vague analyses of Martian terrain," said Mars researcher Nick Hoffman of the University of Melbourne in Australia. Hoffman has championed the "White Mars" hypothesis that portrays Mars as almost always a frigid place where water, as ice, is primarily just another rock.
"One must remember that the Martian terrains that (Stepinski) has analyzed formed over a period of hundreds of millions of years," said Hoffman, "and are still much less mature than terrains in the driest deserts of Earth that are a mere 10 million years old. Therefore, even at its peak, Mars was incredibly dry, by a factor of 10 or 100, than the driest deserts on Earth."
Last week, some other Mars researchers studying the widespread abundance of the mineral grey hematite came to the opposite conclusion in a paper in Nature. Data on grey hematite from the Mars Rovers and Mars orbiting spacecraft appear to support the claim that the planet was once wet and had seas.
On Earth grey hematite is associated with liquid water.
