New type of wave responsible for Y-shape on Venus

Chuck Bednar for redOrbit.com – @BednarChuck

The mysterious ‘Y’ shape that has been seen covering the planet Venus for over five decades is the result of a never-before-seen type of wave being distorted by the planet’s winds, according to new research published in a recent edition of Geophysical Research Letters.

Astronomers have long found Venus to be a mysterious world because its surface is hidden by the planet’s thick clouds, but attempts to examine it in ultraviolet wavelengths of light revealed yet another mystery – a dark, Y-shaped anomaly resting along the equator, said Space.com.

[STORY: Mysterious surface of Venus mapped with Earth-based radar]

That structure covers nearly all of Venus. It has arms that are over 10,500 miles (17,000 km) long and a stem that is 11,900 miles (19,200 km) long. When it was first discovered more than 50 years ago, scientists believed that it was nothing more than clouds blowing in the wind, but data from the 1973 Mariner 10 mission proved otherwise.

Observations from Mariner 10 revealed that the structure not only moved as though it was one single entity, but it traveled at a different speed than its surrounding environment, Space.com said. It is made of a yet-unknown compound that can absorb UV radiation, and by tracking how it moved, experts discovered that the planet’s atmosphere rotates faster than Venus itself.

Y is it there?

While researchers previously believed that the Y feature was caused by waves in the atmosphere, no model of the planet was able to reproduce how it originated and evolved, the website noted. Now, however, scientists at the Institute of Astrophysics of Andalusia in Spain have discovered a new type of wave system that could be responsible for creating the unique and iconic structure.

[STORY: Venus may have had seas of carbon dioxide]

“So far, no model has simultaneously reproduced its shape, temporal evolution, related wind field, nor the relation between its dynamics and the unknown UV-absorbing aerosol that produces its dark morphology,” the authors wrote. “In this paper we present an analytical model for a Kelvin-like wave that offers an explanation of these peculiarities.”

“Under Venus cyclostrophic conditions, this wave is equatorially and vertically trapped where zonal winds peak and extends 7 km in altitude, and its vertical wind perturbations are shown to produce upwelling of the UV absorber. The Y-feature morphology and its 30-day evolution are reproduced as distortions of the wave structure by the Venus winds,” they added.

When a planet spins, Space.com explained, a phenomenon known as the Coriolis effect causes air masses on its surface to apparently deviate on curved paths. Previous studies suggested that atmospheric waves based on this effect may have played a role in creating the Y feature, but lead author Javier Peralta told the website that “the Coriolis effect is negligible on Venus.”

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Peralta and his colleagues discovered that centrifugal forces, which cause items on a spinning object to move away from the center of rotation, could be responsible for creating the Y feature. These forces could cause denser substances to move outward, and the study authors believe that this new wave can cause the currently unidentified UV light-absorbing material on the planet to well upwards, which could explain the dark color of the Y feature.

Shaping up

As for its unusual shape, the Peralta’s team explained that the part of Venus between its equator and its middle latitudes is home to a strong westward-blowing wind that travels at fairly constant speeds. At higher latitudes near the poles, however, they swirl far more quickly, which causes the wave to become distorted and caused the Y-shape appearance of the phenomenon.

The wave exists around the cloud tops of Venus, where the atmospheric winds are at their most intense, not just the planet’s equator. The researchers believe that this could help explain why the Y feature is only seen at altitudes of no more than five miles, and could also shed new light on the behavior of other planets that rotate slowly.

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Source: http://www.redorbit.com/news/space/1113354831/new-type-of-wave-responsible-for-y-shape-on-venus-031815/