Japanese satellite may have spotted largest ever gravity wave on Venus | Science| In-depth reporting on science and technology | DW | 17.01.2017
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Solar System

Japanese satellite may have spotted largest ever gravity wave on Venus

Believed to have been created by the planet's huge mountains and quick winds, the 10,000-kilometer-long gravity wave would be far larger than anything similar recorded in our Solar System so far.

A Japanese meteorological satellite studying the planet Venus may have spotted the largest recorded gravity wave ever in our solar system, after pictures caught a wave 10,000 kilometers in length (more than 6,000 miles) stretched across the planet's surface in December 2015.

After looking at pictures taken while in the planet's orbit, scientists theorize in a paper published in the journal "Nature Geoscience" that the geological bulge may be a gravity wave, due to its ability to remain unaffected by winds of 359 kilometers per hour (223 mph) in Venus' upper atmosphere.

"The present study shows direct evidence of the existence of stationary gravity waves, and it further shows that such stationary gravity waves can have a very large scale - perhaps the greatest ever observed in the Solar System," noted the team in their report.

More than 15 atmospheric gravity waves, known as "bows" to the researchers, have been spotted on Venus before - by the Japan Aerospace Exploration Agency probe Akatsuki and the European Space Agency's own satellites - but the wave spotted in 2015 appeared to be stationary and, at 40 miles above the surface, also appeared to be much higher in the atmosphere than any wave previously recorded.

Not to be mistaken...

An atmospheric gravity wave comes about when a fluid material such as a gas, liquid or plasma is displaced from a position of equilibrium and regularly occurs on Venus as well as our planet. Not to be mistaken for gravitational waves, which are ripples in spacetime, gravity waves tend to come in the form of turbulence in our own atmosphere or surface waves in the ocean.

The study believes that the displacement from atmospheric equilibrium may be caused by Venus' vigorous winds colliding with the huge mountain ranges that exist on the planet's surface.  As the wind flows over the uneven surface of the planet, tension is created between gravity pushing down on air particles being forced up the side of the mountain.

"We suppose that highlands are a key to generating the stationary gravity waves," one of the researchers, Makoto Taguchi, noted. "Because most of the bows - and we have found more than 15 bows so far - have appeared above the highlands at their centres."