Marilyn Monroe had her beauty mark; Jupiter has the Great Red Spot.
It's a powerful storm on the gassy planet's surface that's been observed continually since the 1800s, though it's likely much older than that, and has become the planet's most identifiable feature.
But researchers now say the iconic spot is disappearing. Fast.
"It's at its smallest size ever," said Amy Simon, lead researcher of NASA's Goddard Space Flight Center.
What could be causing the shrinkage? More on that in a bit.
The Great Red Spot is a hurricane-like weather pattern that blows 500 mph winds and swirls clouds of ammonia and ammonium hydrosulphide.
In the 1800s, the GRS, as it's known, was estimated to be 25,500 miles across. Today it's less than half that size.
While it's always been shrinking, Simon said that the process has speeded up dramatically in recent years.
Using data gathered by the Hubble telescope, she calculated the GRS is diminishing by about 580 miles a year.
"People have asked me, 'Is it going to disappear?' But we don't know that yet," Simon said. "It'll be interesting to follow over the next few years and see what it does."
As for the cause, Simon said that small eddies feed into the storm, and they may be changing its internal dynamics, causing the rapid shrinkage.
The real mystery, though, is how a single storm has lasted hundreds of years.
Simon said NASA scientists have tried to recreate the storm in a computer using mathematical models. But even their best efforts weren't able to replicate the longevity of Jupiter's distinctive red spot.
By observing the storm as it shrinks, Simon thinks her team will learn a lot more about how weather works on our solar system's largest planet.