
Two strange, bright flashes on the surface of dwarf planet Ceres may have different origins, according to new infrared images released by Nasa.

The images, captured by the Dawn probe from 28,000 miles (45,000km) away, show that a pair of mysterious spots on the dwarf planet have different thermal properties.

The images were revealed as part of the first colour map of Ceres, showing variations in surface materials, and revealing the diverse processes that helped shape it.

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Ceres may appear to be a drab, grey world, but new infrared images suggest there is more to the dwarf planet than first thought. The latest images are the closest taken yet, and suggest that the icy body was likely once fully active. Images taken using blue (440 nanometers), green (550 nanometers) and infrared (920 nanometers) spectral filters were combined to create the map

'This dwarf planet was not just an inert rock throughout its history. It was active, with processes that resulted in different materials in different regions,' said Chris Russell from the University of California, Los Angeles.

The 'alien' spots on the surface, named feature 1 and feature 5, show up in visible light images as bright flashes in comparison to the rest of Ceres's surface.

In infrared, region 1 is cooler than rest of surface, but 5 is located in a region that is similar in temperature to surroundings.

Last month, scientists said this pair of mysterious bright spots could be towering 'water volcanoes', but they said they need to take a closer look to confirm this.

Federico Tosi, who works on Dawn's Visible and Infrared Spectrometer, presented infrared images of the two spots, measuring their thermal properties.

'What we have found is that bright spot number one corresponds to a dark spot in the thermal image,' he said at a press conference today

Captured by the Dawn probe from 28,000 miles (45,000km) away, the images reveal that two mysterious bright flashes on the surface have different thermal properties. The upper trio is Region 1 at visible, infrared and thermal infrared wavelengths. At thermal infrared, the spot is dark - meaning it is colder than its surroundings. The lower trio represent Region 5. In thermal infrared, the spot disappears

Dawn observed Ceres completing one full rotation, which lasted about nine hours. The images show the full range of different crater shapes that can be found at Ceres' surface: from shallow, flattish craters to those with peaks at their centers

THE MYSTERIOUS WORLD OF CERES Ceres 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'. Scientists think Ceres may have an ocean and possibly an atmosphere. 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. The Dawn spacecraft pulled into orbit last month around the Ceres in the asteroid belt. The probe is currently on the dark side of Ceres and won't emerge until April. There is high interest in the mission because Ceres is one possible destination for human colonisation given its abundance of ice. Advertisement

But feature five, which appears as two separate bright spots next to each other in visible images, didn't show up in the infrared images.

'Spot number five shows no distinct thermal behaviour,' he said. Dawn is currently too far from its target to find out why this is the case, the scientists added. It may be due to having a different structure, or being made from different material.

More detail will emerge after the spacecraft begins its first intensive science phase on April 23, from a distance of 8,400 miles (13,500km) from the surface, said Martin Hoffmann, investigator on the Dawn camera team.

The origins of Ceres' bright spots, which have captivated the attention of scientists and the public alike, remain unknown.

'The bright spots continue to fascinate the science team, but we will have to wait until we get closer and are able to resolve them before we can determine their source,' Russell said.

Recent images from the Dawn spacecraft reveal feature 5 at various angles as the asteroid rotates.

The glimmers of light are visible even when they are near the edge of Ceres, suggesting that they must be high above the surface rather than at the bottom of an impact crater, as previously believed.

'What is amazing is that you can see the feature while the rim is still in the line of sight,' said Andreas Nathues, a planetary scientist at the Max Planck Institute for Solar System Research in Göttingen, Germany.

Ceres rotates in this sped-up movie comprised of images taken by Nasa's Dawn mission during its approach to the dwarf planet. The glimmers of light are visible even when they are near the edge of Ceres, suggesting that are on a high elevation in relation to the rest of the surface

The 'alien' mark can be clearly seen in images the icy world as the Dawn probe hurtled its way towards a rendezvous on March 6

He noted that at dawn on Ceres, the spots shine brightly, but fade as dusk draws in.

According to Nature, this could mean sunlight plays an important role in the formation of the features by, for instance, heating up ice just beneath the surface and causing it blast of in a plume.

Scientists have speculated that the interior of Ceres is rocky with a layer of water and ice.

The leading theory now for the alien spots is that the ice is covered by a thin layer of soil that at times forms into huge 'cryovolcanoes' due to internal pressure in the asteroid.

Ceres is 590 miles (950 km) across and was discovered in 1801. In January, researchers discovered that water was gushing from its surface at a rate of 13lb (6kg) per second.

'Now, finally, we have a spacecraft on the verge of unveiling this mysterious, alien world,' Dawn mission director and chief engineer Marc Rayman, of Nasa's Jet Propulsion Laboratory in Pasadena, California said.

'Soon it will reveal myriad secrets Ceres has held since the dawn of the solar system.'

Ceres is the bright spot in the centre of the image. Because the dwarf planet is much brighter than the stars in the background, the camera team selected a long exposure time to make the stars visible. The long exposure made Ceres appear overexposed, and exaggerated its size A cropped, magnified view of Ceres appears in the inset image at lower left

Dawn will be captured into Ceres' orbit in March, marking the first visit to a dwarf planet by a spacecraft (artist's impression pictured)

Ceres orbits the sun in the asteroid belt between Mars and Jupiter and is very similar to Jupiter's moon Europa and Saturn's moon Enceladus - both considered potential sources for harbouring life.

The presence and abundance of water in bodies like Ceres could have relevance for the origin of life on Earth and the large-scale migration of planets such as Jupiter.

One scenario suggests as the giant planets migrated they disturbed populations of small rocky and icy asteroids and comets which hit the early Earth and Moon - delivering organic molecules and water to Earth.

Ceres is twice the size of Saturn's geyser-spouting moon Enceladus which is suspected of having liquid water beneath its surface.

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.

Since launching in 2007, Dawn has already visited Vesta, a giant protoplanet currently located 104 million miles (168 million km) away from Ceres.

The distance between Vesta and Ceres is greater than the distance between the Earth and the sun.

During its 14 months in orbit around Vesta, the spacecraft delivered unprecedented scientific insights, including images of its cratered surface and important clues about its geological history.

Vesta and Ceres are the two most massive bodies in the main asteroid belt.