The Japanese space probe Akatsuki has delivered its first scientific data about Venus and it turns out that there is much more variety in our neighbor’s atmosphere than we knew.
The discovery made by the Japanese Space Agency (JAXA) involves a huge area of – almost stationary – heated air which extends between the poles in the upper atmosphere.
The JAXA probe Akatsuk arrived in orbit around Venus in 2015 and was then able to observe this phenomenon for three days before losing sight of it on December 12th, 2015, because of a change in Akatsuki’s orbit. When the probe returned to a position to observe the bow-shaped structure on January 15th, 2016, it had vanished.
It seems to hang above a mountain range that pushes up the Venusian air at higher altitudes. But that the heated air remains stationary is odd, since the rest of the atmosphere up there is moving at super-fast speeds with winds surrounding the planet. These winds have speeds of hundreds of kilometers per hour.
The anomaly is probably an atmospheric gravity wave, a ripple in the density of a planet’s atmosphere, according to the European Space Agency. The European Space Agency’s Venus Express spotted several atmospheric gravity waves before the end of its mission in 2014.
Atmospheric gravity waves are similar to waves we see in the ocean, or when throwing stones in a pond, only they travel vertically rather than horizontally. They are essentially a ripple in the density of a planetary atmosphere – they travel from lower to higher altitudes and, as density decreases with altitude, become stronger as they rise. The second type, planetary waves, are associated with a planet’s spin as it turns on its axis; these are larger-scale waves with periods of several days.
The observation by Akatsuki will hopefully provide insight into the turbulent atmosphere of Venus and provide better opportunities for scientists to tweak their models of the extraterrestrial weather condition.
Knowledge about the Venus’ atmosphere can help us understand Earth better too. For example, how this neighbor ours could evolve so different, with a much thicker atmosphere full of carbon dioxide and a mean surface temperature of 735 K (462 °C; 863 °F).
Tetsuya Fukuhara et al. Large stationary gravity wave in the atmosphere of Venus. Nature Geoscience Jan. 16, 2017. DOI: 10.1038 / NGEO2873