ASU researchers have found evidence indicating that oceans never existed on Mars.
Their discovery, published Friday in "Science" magazine, is a conclusion based on seven years of data collected from spacecraft the University has orbiting the Red Planet.
Philip Christensen, ASU planetary geologist, said the study brought a new view to the debate over the past climate of Mars.
"I think it's pretty strong evidence," Christensen said. "We now have hard facts instead of just speculation."
The evidence implied that Mars has always had a cold and relatively dry climate, a contradiction to the warm, wet climate hypothesized by some scientists.
An instrument on NASA's Mars Global Surveyor found only traces of calcium carbonate, a water-related mineral that indicates the presence of oceans or seas.
The absence of this mineral suggests large bodies of water never existed on the planet, Christensen said.
Mars still may have had water, but researchers said it was more likely in the form of glaciers.
The glacier idea "makes more sense," considering the frigid temperatures and significant distance between Mars and the sun, Christensen said.
"Previous to this, we hadn't found any evidence on Mars of carbonate rocks, like limestone," Christensen said. "This gives us two possibilities: that Mars never had oceans, or that our experiments can't see these rocks."
However, the scientists discovered a tiny amount of carbonate minerals in the Martian dust, which showed that the experiment worked, Christensen said.
Since the researchers only found trace amounts of the mineral, the evidence points toward a cold, dry history of the planet. The carbonate is likely a result of the thin atmosphere interacting with dust.
This was the first study that examined the composition of the rocks. Previously, data had been obtained based on surface images of the planet.
ASU currently has two spacecrafts orbiting Mars that send back pictures and data. One left Earth in 1997, the other in 2001.
Reach the reporter at katherine.j.krzys@asu.edu.
