NASA's Cassinni probe reveals the mystery of the age of Saturn's rings. According to one hypothesis, the ring system is more modern than the planet itself, since the stones forming the rings do not have many surface powders coming from space; according to astronomers, the stones are “too clean” for Saturn’s rings to be old. But according to Cassinni's measurements, the dust from space falls very little on the stones of the rings. For seven years, the probe has detected only 140 dust particles falling from outer space to the rings. Astronomers expected it to be much more, but with so few particles the mystery has been resolved: Saturn's ring system is approximately 4.4 billion years old, the same age as the planet.