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It may not be rust that makes the Red Planet red

Researchers are able to replicate Mars' red dust by combining magnetite, which is present in Martian rocks, with sand. The process created the red mineral hematite.

September 19, 2009|John Johnson Jr.

One thing that almost every schoolchild knows about Mars is that it's red. The question is, why?

Until now, the widely accepted scientific explanation has been that the red color of the dust that covers almost everything on Mars results from rocks having been rusted by water.

New research, however, suggests that the planet could have turned red without any help from the water that once flowed across it. Scientists at the Mars Simulation Laboratory at the University of Aarhus in Denmark were able to produce red dust simply by tumbling sand and magnetite, an iron oxide present in Martian rocks, in glass flasks.

"Subsequent analysis of the flask material and dust has shown that the magnetite was transformed into the red mineral hematite through a completely mechanical process without the presence of water," Jonathan Merrison, a researcher at the laboratory, said in a statement. The research was presented this week at the European Planetary Science Congress in Potsdam, Germany.

Matthew P. Golombek, a Mars scientist at the Jet Propulsion Laboratory in La Canada Flintridge, called the new research "an interesting hypothesis. I would say our knowledge of what produced the dust on Mars has always been pretty poor. I don't think we know whether the dust is ancient or new. This is one more very interesting idea."

Many scientists think water played a role in reddening the planet. NASA's rover Opportunity has found evidence that it once flowed in the equatorial region, and twin rover Spirit has turned up indications of long-vanished hot springs. However much water there was, scientists believe it disappeared billions of years ago.

Like places such as Hawaii, Mars is covered with basalt rocks that are rich in iron and can oxidize, or rust, easily when exposed to water. In his lab experiment, Merrison put sand and magnetite in a glass flask and tumbled it over and over. The material gradually changed colors. "Reddish orange material deposits . . . started appearing on the tumbled flasks," Merrison said.

Scientists suspected that as the quartz grains erode, the material is altered. How this happens is not known; Merrison said more research should be done.

"By simulating the conditions and developing accurate analogues of the Martian environment, we will certainly gain a deeper understanding of its dusty nature," Merrison said.


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