The Dawn spacecraft has captured amazing new images of the mystery bright spots on the dwarf planet Ceres, which continue to baffle scientists. In particular, the images show the brightest spot and its companion standing out against the darker surroundings. But experts are still at a loss to explain the composition and source of the bright spots. Scroll down for video . Nasa scientists in California have revealed new images of the dwarf planet Ceres. They reveal new views of the two brightest spots in a crater (shown). However, scientists are still not able to explain what they are. Dawn will begin its first science orbit around Ceres on 23 April . These latest images were taken on 14 and 15 April from a distance of 14,000 miles (22,000km) from the north pole of Ceres. Several theories are currently being touted for what these mysterious bright white spots are on Ceres. The Hubble Space Telescope has found more than 10 on the surface, but Ceres has found that the two most prominent - ‘spot 5’ - are in a crater about 57 miles (92km) wide. One theory is that they are salt flats that are reflecting sunlight, left on the surface by saltwater. Another theory is that they are regions of ice, again reflecting sunlight. Ceres is thought to have plenty of ice beneath its surface, which could be exposed when a asteroid or comet strikes the surface. The fact these bright spots are in a crater - where such an impact occurred - supports this theory. Another possibility is that they are cryovolcanoes - volcanoes that are shooting out water or ice. However, the lack of a raised area around the spots consistent with a volcano suggests this might not be correct. And they could even be water vapour ejecting from a liquid reservoir under the ground, although again current observations - namely a lack of additional material near the spots - suggests this is not the case. As the spacecraft gets closer to the dwarf planet and moves around it, more and more of the surface is coming into view. The two brightest spots seen in a crater are known as ‘spot 5’. The scale in the image is about 1.3 miles (2.1km) per pixel, almost 70 per cent better than previous images. But the origin of the bright spots remains a mystery for now - with theories ranging from exposed ice to volcanoes. Salt flats or ice seem to be the predominant theories at the moment, with the bright spots appearing to reflect incoming sunlight towards the spacecraft’s cameras. Until Dawn gets closer, though, it’s unlikely the mystery will be resolved. ‘It’s too early to say what they are,’ Dr Marc Rayman, Dawn's mission director and chief engineer, told MailOnline. ‘Some people have offered they might be ice, but I don’t consider that necessarily the most likely explanation.’ Dr Rayman says he favours the theory that they could be ‘salty deposits', left over from perhaps saltwater’ on the surface. But one thing that can be ruled out is that they are their own sources of light. Dr Rayman is certain they are simply reflecting sunlight. ‘They’re mysterious but not bizarre,’ he said. This animation, made using new images taken by Dawn, shows how the bright spots become visible when they pass the 'terminator' - the line where the planet is split between sunlight and darkness. Credit: Nasa . In this close up view, the two different spots can clearly be seen. Several theories currently exist for what they might be, with the favoured being salt flats or ice - both reflecting sunlight . Nasa's Dawn spacecraft (artist's illustration shown) made its way to Ceres after leaving the asteroid Vesta in 2012. There is high interest in the mission because Ceres is seen as being a record of the early solar system, and may also have shifting ice on its surface . Ceres is 590 miles (950 km) across and was discovered in 1801. It is the closest dwarf planet to the sun and is located in the asteroid belt, making it the only dwarf planet in the inner solar system. Ceres is the smallest of the bodies currently classified as a 'dwarf planet'. It lies less than three times as far as Earth from the sun - close enough to feel the warmth of the star, allowing ice to melt and reform. Nasa's Dawn spacecraft made its way to Ceres after leaving the asteroid Vesta in 2012. There is high interest in the mission because Ceres is seen as being a record of the early solar system, and may also have shifting ice on its surface. Dawn continues to get closer to the dwarf planet and on 23 April it will descend to a circular orbit 8,400 miles (13,500km) above the surface. It will then begin its first mapping phase of the dwarf planet in this so-called science orbit, travelling from pole to pole to image the entire surface. Three more science orbits are planned, with the spacecraft mapping the comet in increasing detail. Up until December it will periodically descend lower and lower until it reaches an altitude of just 225 miles (260km) above the surface, with images 100 times better than those taken so far. This is lower than the orbital height of the ISS around Earth – and will allow Dawn to snap glorious images of Ceres’ surface, including its mysterious bright spots. These latest images (close up view of the bright spots in the crater on the right) were taken on 14 and 15 April from a distance of 14,000 miles (22,000km) from the north pole of Ceres . Dawn is continuing to get closer to the dwarf planet Ceres (position in the solar system shown left), and on 23 April it will descend to a circular orbit 8,400 miles (13,500km) above the surface - its first science orbit. Three more are planned by the end of the year (orbital paths shown right) ‘The approach imaging campaign has completed successfully by giving us a preliminary, tantalising view of the world Dawn is about to start exploring in detail. It has allowed us to start asking some new and intriguing questions,' said Dr Rayman said in a statement. Dawn became the first spacecraft to orbit a dwarf planet on 6 March, having left the giant asteroid Vesta in 2012. Both Vesta and Ceres are in the main asteroid belt between Mars and Jupiter, and were on their way to forming planets before their development was interrupted - likely by the gravity of Jupiter.
Nasa scientists in California reveal new images of dwarf planet Ceres.
They show new views of the two brightest spots in a crater.
However, scientists are still not able to explain what they are.
Dawn will begin its first science orbit around Ceres on 23 April.