Uranus (left) and Neptune (right) are different shades of blue despite the many similarities they share in terms of mass, size and composition. (Image: NASA) For decades, scientists have classified Uranus and Neptune as “ice giants” – massive outer planets believed to contain large amounts of icy material beneath their atmospheres. But new research is challenging that long-held understanding, suggesting the two planets may contain far more rock-rich material in their interiors than previously thought. Researchers say the findings could reshape how scientists understand the composition of the two distant planets. “We found out that both Uranus and Neptune have their outer shells made mostly of rocks (and hydrogen and helium gas). This goes against the common belief that they are ice-giant planets,” author Yamila Miguel of the Netherlands Institute for Space Research told Space.com .…