Scientists have spotted a 1,000-mile-long stretch of 'complex' terrain, alongside some unexplained polygonal features, in images taken from 3.3 million miles (5.4 million km) away. These features sit alongside an immense dark band known as the 'whale' alongside a heart-shaped lighter patch on the surface (inset). Researchers believe the 'heart' may be an icy regions of frozen nitrogen, methane and carbon monoxide.