Astronomers have spotted a bulge on Venus' atmosphere which might have been caused by the largest gravity wave ever witnessed in the Solar System.

Discover Magazine said gravity waves are upheavals in a planet's atmosphere caused by winds colliding with features on the surface.

But what intrigues the scientists most is not the bow-shaped bulge but how it can withstand the treacherous climactic and atmospheric condition of the planet. More so, how it was able to form high above the surface. Venus' upper atmosphere moves at a staggering 100 meters per second.

According to Science Alert, the bulge, which was discovered by Japan Aerospace Exploration Agency (JAXA) Akatsuki probe in 2015, stretched from Venus' north to south pole. It remained for four days straight at about 65  km (40 miles) above the surface, withstanding the hot surface of Venus and and 359 km/h (223 mph) winds. An image of the bulge was detected using both infrared and UV imaging.

Similar structure was observed by the team over the succeeding years of their mission. Scientists suspect that what lies below Venus' atmosphere has something to do with it.

Tech Times said that the mountainous characteristics on the surface of Venus are potentially forcing winds into the upper atmosphere, a place where they slow down to form a wave, such as what was seen by the Japan's probe. The bulge is, in fact, located above the continent-sized highland region called Aphrodite Terra.

"Some researchers have imagined that a gravity wave excited in the lower atmosphere may reach the upper cloud deck or higher in the Venus atmosphere, but no direct evidence of that has been found before," Makoto Taguchi of Rikkyo University in Tokyo, a coauthor of the study, writes in an email to Christian Science Monitor.

"This is the first evidence of gravity wave propagation from the lower atmosphere to the middle atmosphere. This means that conditions of the lower atmosphere may affect the dynamics of the higher atmosphere by momentum transfer of the gravity waves."

Evidence of gravity waves has been spotted on Venus before by European Space Agency's Venus Express mission. However, Colin Wilson, an atmospheric scientist at Oxford University who was not involved in the paper told Christian Science Monitor that it did not capture images the way the Japanese spacecraft did.

The researchers discuss their findings in a paper published Monday in Nature Geoscience.