Washington D.C., March 26 -- : Eight and a half years into its grand tour of the solar system, NASA's Voyager 2 spacecraft was ready for another encounter. It was January 24, 1986, and soon it would meet the mysterious seventh planet, icy-cold Uranus.

Over the next few hours, Voyager 2 flew within 50,600 miles (81,433 kilometres) of Uranus' cloud tops, collecting data that revealed two new rings, 11 new moons and temperatures below minus 353 degrees Fahrenheit (minus 214 degrees Celsius). The dataset is still the only up-close measurements we have ever made of the planet.

Three decades later, scientists reinspecting that data found one more secret.

Unbeknownst to the entire space physics community, 34 years ago Voyager 2 flew through a p...