Geology Upset: Wind Carves Canyons Fast
According to a new study, wind carves canyons ten times faster than water. This has implications for theories on Mars and Earth.
Ancient canyons scar the surface of Mars, a relic from a time billions of years ago when rivers flowed on its surface. But water may not be the only factor that shaped these canyons—the wind whipping through them could be just as important, according to a new study of river canyons on Earth. Scientists studying chasms in the Andes mountains in northeast Chile have found that wind carves some canyons 10 times faster than water. The discovery may be significant for understanding how much water flowed on the surface of ancient Mars.
The rates at which wind can carve canyons “has not been well understood,” Conover says. Studies of the canyons in Chile near the very-dry Atacama Desert allowed geologists to estimate the contribution of aeolian erosion. Wind-carving tends to form long straight canyons like “cat scratches,” whereas water erosion forms amphitheater-shaped headwalls, they concluded. But it may be hard to tease out the causes for a particular canyon due to obstacles like mountains.
The article does not mention the granddaddy of Mars canyons, Valles Marineris—so vast, it could stretch across the United States. But planetary scientists and astrobiologists will have to be careful when inferring the amount of water on Mars.
The canyons [studied here on Earth] lie at the edge of the Atacama Desert, where the extremely dry, windy climate provides optimal conditions for the formation of wind-scoured canyons. Sandblasting wind gusts could shape canyons on the similarly parched surface of Mars as well, the researchers point out. Martian winds have shifted sand dunes and scoured bedrock, but when it comes to Mars’s canyons, scientists have usually assumed that water was the dominant shaping force. The new study indicates this might not be the case.
On Mars, “it’s been dry for so long that the channels might have been modified by quite a lot” by wind, says geomorphologist Ken Ferrier of the Georgia Institute of Technology in Atlanta, who was not involved with the study. But if scientists have been discounting this effect, “our attempts to estimate how much water used to be flowing on Mars … might be pretty strongly biased,” he says. If wind has expanded the canyons of Mars, scientists might overestimate how much water once flowed there if they neglect the effect of wind.
It was known since the first years of space exploration that Mars is sometimes completely enveloped by dust storms. The atmosphere, however, is only 1% that on Earth, so its erosive power is weaker.
Understanding the influence of wind on canyon formation will require more research, Conover says. Nathan Bridges (Johns Hopkins) commented that the study “provides us some good food for thought for trying to understand Mars.”
Conover did not mention Titan, Saturn’s large moon. But since its atmosphere is denser than Earth’s and it also has winds strong enough to form sand dunes, these findings may affect theories of that world’s canyons and channels as well.
This article is not too useful for estimating the age of Mars, since the researchers still feel the winds have blown for millions of years. It does show that some features may have formed ten times more rapidly than previously thought. The primary lesson here is another case of faulty assumptions and failing to recognize the power of an unknown (or ignored) factor.
Another observation (illustrated by Conover’s first sentence) is that many secular news articles start with moyboy lingo (“millions of years, billions of years”) only to launch into a discussion of facts that undermine it. This happens in Darwinian articles, too: “this evolved; that’s a fact. But….” It’s like the author has to show a badge to get in the door, then once inside, is free to discuss contrary data. We should coin a word for this behavior. Send in your suggestion for a new entry in the Darwin Dictionary. This entry was sent in by Pat: “D-Merit Badge” (D for Darwin). Good one!