Winds of change
Suffice to say, planetary geologists classify such proof-of-life observations as dubious. Claims of Banyan trees and changing vegetation patterns are suspect.
"I've looked at a lot of the MGS images. That's what I do. I'm afraid I don't see any diagnostic evidence that would support these claims. It doesn't mean it's not worth looking and thinking about. But we don't have the data today to support such contention," said Ron Greeley, a leading planetary scientist at Arizona State University in Tempe.
Richard Zurek, a Mars researcher at the Jet Propulsion Laboratory in Pasadena, California, warns that Mars is a different world contrasted to Earth. "We really have to be careful about drawing too tightly on our terrestrial analogs," he said.
Zurek said that taking just a single image and stirring in speculation is inadequate. "You need to look at all the data and bring all the data to bear," he said.
Seasonal processes on Mars can deceive the eye, Zurek said. Wind moving a thin veneer of dust around, he said, can make the Martian surface look very different from one period of time to another.
"So right now, I haven't seen any evidence that really points to vegetation as being an explanation for what we see. There are alternate explanations, like the wind blowing across the planet," Zurek said.
The Mars way
Many of the big compelling questions regarding Mars' formation and evolution can only be answered by getting astronauts to the surface and conducting detailed geologic investigations, said James Rice, a planetary geologist at Arizona State University in Tempe.
"Most of the images in question that I looked over are of dunes in the polar regions. They are beginning to defrost as winter draws to a close. The sand composing the dunes is dark and frost is bright, thereby causing the spotted pattern as the dune defrosts. This is not vegetation but rather the natural defrosting of dunes and sand sheets," Rice said.
Whatever the case for current life on Mars, future spacecraft and eventual human exploration are sure to play out the full story.
"Mars is a geologically complex and diverse world with a plethora of geological mysteries and questions. However, we will be able to address these questions with further detailed exploration of this world," Rice said. "The best geologist to send to Mars is not robotic but rather human," he said.
James Garvin, lead scientist for NASA's Mars Exploration Program, said misinterpretation of images is far too easy to do. Tricks of illumination can skew the truth. Also, MGS images can be processed in ways that highlight certain features, so care should be taken in evaluating the Mars photos, he said.
"Mars is a challenging world. It can dupe us," Garvin said. Whether it's the atmosphere, climate, ice caps, clouds, or similar looking surface features, putting too much trust in analogies to Earth can lead you down wrong roads, he said.
"On Mars, maybe Mars found the Mars way," Garvin said.
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