There’s a mystery at the edge of our solar system: Two spacecraft, Pioneers 10 and 11, which were launched to Jupiter and Saturn more than 30 years ago, are hurtling towards the edge of our solar system – but at a slower than expected rate. Called the Pioneer Anomaly, the effect of this slowing is small, but measurable, and so far unexplained.—TPS Enables Study Of Mysterious Pioneer Anomaly