There's a chance 2015 will go down in astronomy as the year of the dwarf planets. New Horizons' study of Pluto and the Dawn mission around Ceres have provided scientists with a heap of information about the smaller (but no less important) members of the Solar System. The latest data from Ceres hints at an even more surprising connection to Pluto: Ceres might have formed in the same area of the solar system as its much more distant cousin.
Astronomers have identified specific minerals on the surface of the dwarf planet that are unlikely to have formed in Ceres’ current location in the middle of the asteroid belt. By looking at the spectrum of the object in visible and infrared light, the team discovered ammoniated phyllosilicates to be widespread around Ceres. Ammoniated phyllosilicates are substances created when ammonia interacts with materials such as clay.
Speaking to IFLScience, Dr Maria Cristina De Sanctis, lead author of the study, explained how these substances actually form. “Ammoniated phyllosilicates are formed by alterations of primordial material [from which the Solar System formed] that contained ammonia, and these alterations are able to constitute both phyllosilicates and ammonium phyllosilicates,” she said. “Some phyllosilicates are formed from water and even earlier rocky material.”
And Ceres is not the only object in the asteroid belt that's rich in ammonia. “We fit the spectrum of Ceres using ammonium phyllosilicates for a specific band which is also present in another couple of bodies in the main belt,” De Sanctis added.
In this artistic impression, two different hypotheses regarding the formation of Ceres are presented: in the asteroid belt, or much further out. L.Giacomini
The research letter, published this week in Nature, proposes two mechanisms to explain the presence of ammonia on Ceres. The planet is too close to the Sun for the ammonia to have stayed there since the formation of the Solar System, as ammonia ice is only stable at cold temperatures. The abundance of ammoniated phyllosilicate indicates that either Ceres formed in the outskirts of the Solar System and then migrated inwards, or it has been subjected by a consistent rain of small objects, referred to as pebbles, from beyond the orbit of Neptune.
De Sanctis doesn’t exclude a collision with some heftier objects, like comets. “Some recent models shows lots of pebbles coming from the outer Solar System, but [the ammonia enrichment] doesn’t have to come from pebbles alone.”
There is no follow-up observation planned to clarify the mysterious origin of Ceres, but a lot more scientific data is coming from the Dawn spacecraft.
“We are still in orbit around Ceres, and we will do a lot of other observations,” said De Sanctis. “I’m not sure what we will be able to see which can tell us more about its origin. We have a lot of other things to look at, for instance, the internal structure. Other instruments will give us more information about the key elements of Ceres and we could have more details that will help us in discriminating the origin of Ceres.”
Another piece of research published today suggests Ceres is more comet-like in its characteristics than previously thought, and supports both theories for its formation mentioned earlier.