The debate has raged for decades -- was the Red Planet once blue? Now the theory that a vast ocean once covered a third of Mars has received a big boost with a study that suggests wobbles in the planet's rotation caused massive distortions of ancient coastlines. The findings by Harvard University planetary scientist J. Taylor Perron and colleagues offer an intriguing explanation for surface anomalies that have provided nay Sayers with the best arguments against the existence of Martian seas. Photos snapped from space and on the surface show what appear to be shores of a vanished sea. But in the 1990s, mapping of the Martian topography by NASA's Mars Global Surveyor measured an undulating shoreline of wildly varying heights, an impossibility if an immense body of water was contained. Now comes Perron with an elegant explanation based on computer models: Something -- perhaps the impact of huge asteroids -- caused Mars to literally "topple" sideways more than a billion years ago, with the axis of the planet shifting 50 degrees to the north. The result was fantastic topographical changes as heavier masses on the surface and beneath the crust were shifted toward a new equator by the planet's changed spin. Shorelines would have heaved, buckled, and cracked. "We don't know what caused the 'polar wander,' but possibilities include a volcanic eruption that moved a large amount of magma from the interior to the surface," Perron said in an interview.
BOTTOM LINE: The case for an ancient ocean -- or oceans -- on Mars is much stronger.
CAUTIONS: There is still the perplexing question of how an ocean could vanish, even over geological stretches of time. Calculations show that if the giant basins visible on Mars did contain water, the quantity would have been far too much to have simply evaporated into space.
WHAT'S NEXT: Perron is seeking to determine what might have caused the dramatic reorientation of Mars relative to its rotation pole. And he's hoping this will be the emphasis of future NASA probes of the planet next door. "This new support for the ocean hypothesis will help to guide upcoming Mars missions, both in orbit and on the surface," he said.
WHERE TO FIND IT: Nature, June 14.
Twitching eyes could aid recognition of fine details
The tiny, involuntary movements of our eyes might help us recognize finely detailed images, researchers at Boston University have found. Our eyes are constantly in motion. Scientists hypothesized as early as a century ago that such spasms aid the eyes with challenging tasks such as reading the fine print of a document or looking for a hummingbird in a field of flowers. New technology allowed Dr. Michele Rucci and colleagues to test this theory, using a computer program that cancelled out the effect of study subjects' eye movements by shifting a picture at the same time and in the same direction. The researchers asked subjects to tell them whether short lines projected onto a gray background were angled to the right or to the left. When the lines were close together, viewers had an easier time determining the pattern's direction with normal eye movement than with their movements counteracted by the computer. They guessed correctly 79 percent of the time, compared with 63 percent without eye movement. There was no significant difference when the lines were farther apart. Previous studies had found the opposite -- that the eyes' twitching was more useful in seeing widely-spaced patterns such as the grid on a sidewalk than the densely-packed dots of an Andy Warhol painting. But those studies used an earlier technique that required participants to gaze for long periods, tiring their eyes and potentially distorting the results.
BOTTOM LINE: Jiggly eye movements might help the brain understand what we see.
CAUTIONS: Six people participated in the study. All had normal vision, meaning the results might not be valid for people who are near-sighted or far-sighted.
WHAT'S NEXT: The findings could help scientists develop treatments for conditions that involve abnormal eye movement, such as dyslexia.
WHERE TO FIND IT: Nature, June 14