What a Japanese spacecraft saw on Venus is literally a huge discovery

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Jan 25, 2017

Space may be crawling wtih leviathan stars and gargantuan black holes in distant galaxies, but Japanese spacecraft Akatsuki has revealed evidence of having observed something colossal only tens of millions of miles from Earth: what could possibly be the most enormous gravity wave in our solar system.

JAXA (Japanese Aerospace EXploration Agency) has recently released Akatsuki images from 2015 and 2016 along with the results of a study published in Nature Geoscience. The spacecraft used its Longwave Infrared Camera and Ultraviolet Imager to capture the phenomenon, which appeared as a blazing bow-shaped wave that surprisingly remained unmoving for days on end despite being lashed by 220-mph winds high in the sulfurous clouds of Venus. Its possible origins could demystify what lies deeper in the poisonous Venusian atmosphere.

Gravity waves, not to be confused with the ripples in space-time otherwise known as gravitational waves, arise from the disturbance of liquid, gas or plasma by an obstacle. Earth sees incidences of this when wind blows over a mountain. However, with a longitude of 6,000 miles north to south, the gravity wave that was caught hovering over Venus' Aphrodite Terra highlands is larger than any ever recorded on Earth. It also managed to stay abnormally still for an unheard-of 96 hours on a planet swirling with violent jet-stream winds.

Fierce winds were once thought to exist only on the top layer of Venus' atmosphere. Like a sleeping dragon, these blasts of scorching air were thought to calm down significantly once you plunged deeper (at least for anyone who could stand breathing noxious gases while being roasted alive in their space suit). Scientists now conclude that it is nearly impossible to equate a gravity wave of this size with milder winds in the lower atmosphere of Venus, instead theorizing that these winds must be more temperamental than previously thought.

Team lead Makoto Taguchi of Tokyo's Rikko University believes Venus is keeping secrets in her lower atmosphere. "The formation and propagation of a mountain gravity wave remain difficult to reconcile with assumed near-surface conditions on Venus," stated Taguchi and colleagues in Nature Geoscience. "We suggest that winds in the deep atmosphere may be spatially or temporally more variable than previously thought." He believes that winds coursing over the planet's mountainous surface generated this gravity wave, which then transmitted to the upper atmosphere. How frequently gravity waves of this magnitude occur on Venus is still unknown.

Akatsuki, whose name translates to "Dawn" or "Daybreak" (an appropriate satellite for a planet nicknamed "the Morning Star"), entered orbit around Venus in 2015 after narrowly missing on its first attempt. Because the planet spins in retrograde and extremely slowly, a day on Venus is longer than a year, which is why it took Akatsuki a considerable length of time to line up with the Aphrodite Terra region where the gravity wave was discovered. It is the lone intrepid spacecraft orbiting Venus after NASA turned down two proposals for its own Venus mission.

(via Spaceflight Now)