In a span of four years, the hexagon formation on the Northern hemisphere of Saturn turned from blue to gold. The changing color baffles NASA scientists as they struggle to understand what caused the drastic changes in Saturn's surface.

There is an ongoing 20,000-mile storm at Saturn's North Pole and it has intrigued scientists ever since it was discovered. But what's causing more confusion is that the 'hexagon' changed colors upon comparing images taken of Saturn's North Pole from 2012 to 2016. From the images released by NASA, it is evident the once blue color turned into yellowish-gold.

The Cassini spacecraft observing the planet since 2004 captured the images. The change appeared to happen gradually based on the observation launched since Nov. 2012 up to Sept. 2016.

The mystery hexagon is a cloud pattern in Saturn's northern hemisphere where an evident weather activity is taking place. Experts believe that the shape could have been caused by the varying wind speed in Saturn.

Saturn, the second largest planet in the Solar System next to Jupiter, is also a gas planet. It is composed mainly of hydrogen, methane, and helium. But despite the surprising changes, astronomers and scientists already offered some potential causes of the unusual phenomenon.

"In particular the change from a bluish color to a more golden hue may be due to the increased production of photochemical hazes in the atmosphere as the north pole approaches summer solstice in May 2017," a NASA official said in a statement.

Some say that the change in color can be attributed to the planet's changing season. The color may vary depending on the amount of sunlight that is responsible for producing aerosols in the planet's atmosphere.

 "In particular, the change from a bluish color to a more golden hue may be due to the increased production of photochemical hazes in the atmosphere as the north pole approaches summer solstice in May 2017," a NASA official said in a statement.

The hexagon shape that changes in color could also be a six-sided Jetstream that prevents particles from the outside to penetrate the planet. But there aren't enough evidence or studies yet to help confirm if the theories are correct.

One thing is for sure, though, the unusual hexagonal shape on the tip of Saturn obviously changed its color and that is something for astronomers and scientists to figure out in the years to come.