Scientists were puzzled by mysterious twinkling bright light coming from the dwarf planet Ceres. It seems that scientists have finally discovered what causes these lights.
Data received from the unmanned spacecraft have led to two new studies, published in the journal Nature, which give purely scientific explanations for the bright patches.
One study identifies this bright material as a kind of salt, while the second study suggests the detection of ammonia-rich clays, raising questions about how Ceres formed.
Study authors, led by Andreas Nathues at Max Planck Institute for Solar System Research, Göttingen, Germany, said the bright material is consistent with a type of magnesium sulfate called hexahydrite – a different type of magnesium sulfate is familiar on Earth as Epsom salt.
The team believe the salt-rich areas were left behind when water-ice sublimated in the past and then impacts from asteroids would have unearthed the mixture of ice and salt.
Mr Nathues said: “The global nature of Ceres’ bright spots suggests that this world has a subsurface layer that contains briny water-ice.”
The surface of Ceres, whose average diameter is 584 miles, is generally dark, similar in brightness to fresh asphalt.
The biggest bright area, about six miles across and 0.3miles deep, is in the centre of a crater called Occator, itself is 60 miles in diameter. Occator appears to be among the youngest features on Ceres at a mere 78million years old.
The study found in some images Occator “appears to show a diffuse haze near the surface that fills the floor of the crater”.
“The haze seems to be present in views during noon, local time, and absent at dawn and dusk, study authors write.
“This suggests that the phenomenon resembles the activity at the surface of a comet, with water vapour lifting tiny particles of dust and residual ice.”
In the second study, members of the Dawn science team examined the composition of Ceres and found evidence for ammonia-rich clays.
They used data from the visible and infrared mapping spectrometer, a device that looks at how various wavelengths of light are reflected by the surface, allowing minerals to be identified.
The spokesman said: “Ammonia ice by itself would evaporate on Ceres today, because the dwarf planet is too warm.
The presence of ammoniated compounds raises the possibility that Ceres did not originate in the main asteroid belt between Mars and Jupiter, where it currently resides, but instead might have formed in the outer solar system.
Another theory is that Ceres formed close to its present position, incorporating materials that drifted in from the outer solar system – near the orbit of Neptune, where nitrogen ices are thermally stable.
The study also shows that daytime surface temperatures on Ceres span from minus 136 degrees to minus 28 degrees Fahrenheit (180 to 240 Kelvin). The maximum temperatures were measured in the equatorial region.
This week Dawn reached its final orbital altitude at Ceres, about 240 miles above the surface.
In mid-December, Dawn will begin taking observations from this orbit, including images at a resolution of 120 feet per pixel, for the best pictures yet, and infrared, gamma ray and neutron spectra, and high-resolution gravity data.