Scientists working on NASA’s Dawn mission have found evidence of ammonia-rich clays on Ceres that raises questions over the origins of the dwarf planet.
It had been thought to have originated in the main asteroid belt between Mars and Jupiter, where it exists today.
But the presence of ammoniated compounds raises the possibility that it might have formed in the outer solar system. Either that, or Ceres could’ve formed close to its present position, but incorporated materials drifting in from the outer solar system near the orbit of Neptune.
The study is published in Nature today, one of two reports on Ceres based on data from Dawn’s fly-by earlier this year. The other identified what causes the dwarf planet’s mysterious bright spots.
The team used data from the visible and infrared mapping spectrometer to identify the ammonia-rich clay. Ammonia ice by itself would evaporate on Ceres molecules could be stable in combination with other minerals.
“The presence of ammonia-bearing species suggests that Ceres is composed of material accreted in an environment where ammonia and nitrogen were abundant. Consequently, we think that this material originated in the outer cold solar system,” said Maria Cristina De Sanctis, lead author of the study, based at the National Institute of Astrophysics, Rome.
Dawn has now reached its final orbital altitude, about 385 kilometres above the surface of Ceres.
Bill Condie is a science journalist based in Adelaide, Australia.
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