The mystery of Ceres’s bright spots has deepened, scientists reveal.
A dwarf planet measuring 950 km in diameter, Ceres is the largest object in the asteroid belt - a disc of rocky objects that sits between the orbits of Mars and Jupiter. Its gleaming patches were captured by Nasa’s Dawn space probe as it hurtled towards the dwarf planet last year, leading to a scramble within scientific circles to explain the phenomenon.
But the mystery appeared to have been solved when, in December last year, a team of researchers reported that they had found evidence that the bright patches on the dwarf planet are formed from hydrated magnesium sulphate. Further, a haze observed within the 90km-wide Occator crater was thought to be down to dust, ice particles and water vapour produced when the sun’s rays hit the surface of Ceres, warming a layer of ice beneath. This haze was been found to be present at the dwarf planet’s noon but not at its dusk - an effect that ties in with exposure to solar radiation.
But new research suggests there might be more to the mystery. Using data from the High Accuracy Radial velocity Planet Searcher (Harps) spectrograph at the European Southern Observatory in Chile, a team of scientists have followed Ceres as it spins on its axis, monitoring the spectrum of the light reflected by the dwarf planet on the 31st July 2015 and again on the 26-27 August.
In a paper published in the Monthly Notices of the Royal Astronomical Society, the team reveal that while they saw evidence that crater brightened and dimmed on 31st July - an effect thought to be down to reflections from changing levels of haze - they saw no change during their August observations.
According to Dr Paolo Molaro of the Trieste Astronomical Observatory, an author of the new study, the fact that reflections from the Occator crater were much reduced in August could suggest that the layer beneath the crater’s surface is not replenished in a continuous process. But Molaro is quick to point out that further studies will be needed to confirm his suspicions. “These are all speculations for the moment,” he warns.
