The colors of Jupiter’s atmosphere are created when different chemicals reflect the Sun’s light. Most of Jupiter is hydrogen and helium, but the top of its clouds are composed of ammonia crystals, with trace amounts of water ice and droplets, and possibly ammonium hydrosulfide. Powerful storms on Jupiter are created by the planet’s convection. That allows the storms to bring material, such as phosphorus, sulfur and hydrocarbons, from closer to the planet’s core to the tops of the clouds, causing the white, brown, and red spots that we see dotting the Jovian atmosphere. White spots appear to be cool storms, brown are warm, and red are hot storms.
Jupiter’s Great Red Spot is an extreme example of one of these storms. It has been raging for at least 400 years. It is thought to have first observed by Giovanni Cassini in the late 1600s. It was observed up close by NASA’s Pioneer 10 spacecraft when it made its flyby in 1974. Better and better images were captured by other spacecraft, including the Voyagers, Galileo, Cassini and New Horizons. A century ago, the Red Spot measured 40,000 km across, but now it measures roughly half that, and seems to be shrinking. Astronomers have no idea how long the spot will last nor why it has lasted so long. The storm is so large that it can be seen from Earth by any medium sized or larger telescope.
A more recent storm has developed on Jupiter that has captured the attention of astronomers. Officially dubbed Oval BA , but commonly referred to as Red Jr, this storm is about half the size of the famous Great Red Spot and almost exactly the same color. Oval BA first appeared in 2000 when three smaller spots collided and merged. Scientists theorize that the Great Red Spot may have been created in the same way.
Scientists have been using the color of Jupiter to understand the atmospheric workings of the planet. There are future missions scheduled to bring a more in depth understanding to light. Those missions are also going to study the interaction of the volcanoes on Io with the water ice on Europa. There should be some pretty awesome data coming in the next few years.