Astronomers on Earth will have ringside seats to a face-off between two of the biggest storms in the solar system.
In one corner will be Jupiter's Great Red Spot, a behemoth of a tempest that is twice as large as Earth and whose 350 mph winds have been whirling for hundreds of years.
Its contender will be Oval BA, also known as "Red Jr.," a young six-year storm that is only half Great Red's size but whose winds are just as fierce.
The two are approaching each other now and are expected to have their closest approach on the Fourth of July, according to Amy Simon-Miller, an astronomer at Goddard Space Flight Center in Maryland who has been monitoring the storms.
"There won't be a head-on collision," Simon-Miller said. "The Great Red Spot is not going to 'eat' Oval BA or anything like that."
However, the storms' outer bands are expected to pass close to one another and it's anybody's guess what will happen when they do.
This isn't the first time that such an encounter has happened. In fact, the two storms typically pass each other every two years or so. Similar encounters happened in 2002 and 2004, but they were very anti-climactic. Aside from some "roughing" around the edges, both storms came out unscathed.
This time might be different, however, said Simon-Miller. Red Jr. could revert to its original color and change from red to white. From 2000 to 2005, Red Jr. was actually white and no different from the many other small "white ovals" circling the planet.
But in 2006, astronomers noticed a change: a red vortex formed inside the storm, the same color as the powerful Great Red Spot. Scientists believe the color change was a sign that the storm was intensifying.
Scientists think the Great Red Spot could push Oval BA toward a southern jet stream on the planet during their upcoming encounter. The jet stream blows against Oval BA's counterclockwise rotation and could slow its spin, possibly changing the storm's color back to white.
The color of the Great Red Spot itself is a mystery. According to one popular theory, the storm dredges up material from deep inside Jupiter's atmosphere, lofting it above the highest clouds where ultraviolet rays from the Sun turn color-changing compounds, called "chromophores," red.