Developments in Brief : Scientist Says Streaks on Mars May Be Tracks Left by Tornado-Like Storms

Peculiar dark streaks running up to 50 miles across the surface of Mars may be the result of tornado-like winds generated by storms similar to those that produce twisters on Earth, a Brown University planetary scientist says.

The winds apparently scoured the Martian deserts and left tracks of coarse material darker than the surrounding terrain, according to Prof. Peter Schultz.

His storm scenario is based on pictures of Mars taken by the two satellites that accompanied the Viking robot landers to Mars in 1976. Those pictures showed hundreds of streaks. Scientists previously had interpreted them as linear sand dunes or joint patterns. But Schultz cast doubt on those interpretations in a report in the current issue of Science magazine

He said several clues suggest that the streaks are tracks of “intense atmospheric vortices,” which would be tornadoes on Earth. The streaks are half a mile wide and range in length from about a mile to nearly 50 miles. They are straight or slightly curved, have gaps that have nothing to do with topography and seem to be a seasonal phenomenon, according to Schultz.

He said the streaks appear to form in the late summer in the southern hemisphere of Mars. That is the time when the thin Martian atmosphere clears of sand storms, allowing the sun to heat the planet’s surface. That in turn forms warm air beneath cold air to create an unstable condition. This also is the time of the Martian year when storm systems develop, creating a complex set of atmospheric conditions like those that can lead to tornadoes on Earth, he said.

The researcher said a new Mars satellite called Mars Observer, which NASA plans to launch in 1992, should be able to produce pictures with enough detail to enable scientists to determine if the streaks are actually tornado tracks.