NASA's Dawn mission which is exploring Ceres has found that the dwarf planet's surface is composed of ice, salts and hydrated materials, providing sufficient clue that the planet had oceans in its past.
Another research found that there are softer, easily deformable layers beneath Cere's rigid crust surface. This finding also gives hope for the presence of liquid below the surface which could be the leftover of an ocean.
Julie Castillo-Rogez, Dawn project scientist who is based at NASA's Jet Propulsion Laboratory, Pasadena, California, said, "More and more, we are learning that Ceres is a complex, dynamic world that may have hosted a lot of liquid water in the past, and may still have some underground."
The scientists, however, are not willing to land the Dawn on Ceres as it might be technically challenging. A landing in the dwarf planet might also result in contaminating it.
The Dawn has been studying Ceres from its orbits. The probe is currently focusing in the dwarf planet's gravity to estimate its composition and interior structures.
A study led by Anton Ermakov, a postdoctoral researcher at JPL, determined the internal structure and composition of Ceres using shape and gravity data measurements from the mission. Measurements using NASA's Deep Space Network helped to track small changes in the spacecraft which gave the observations.
According to the study, published in the Journal of Geophysical Research: Planets, Ermakov's team have found that the Ceres was geologically active at least in the past. The research paper says that the dwarf planets have three crates and a solitary mountain Ahuna Mons. The craters Occator, Kerwan and Yalode and the Ahuna Mons are associated with "gravity anomalies".
The Dawn's observation about the gravity of Ceres was different from the calculations made by the scientist's models. These discrepancies which were observed from the four locations of the dwarf planet are believed to have resulted from the subsurface activities.
Ermakov said, "Ceres has an abundance of gravity anomalies associated with outstanding geologic features."
Cryovolcanism, where a volcano ejects water, ammonia or methane, is believed to be the cause of this abnormality in the Ahuna Mons and the Occator. These geological activities might have resulted in the formation of these structures. The studies have found that the density of Ceres crust is lower than rocks and had similarities to ice.
However, another study by Michael Bland of U.S. Geological survey stated that the Ceres' crust is strong and ice cannot be a major component which could form the planets' surface. The scientists are deepening their research with their confusions about the dwarf planets' surface which has the density similar to ice but is stronger at the same time.
Another model of Ceres states that its surface evolved with time to turn as a unique one. The study led by Roger Fu at Harvard University in Cambridge, Massachusetts and published in the journal Earth and Planetary Science Letters, was based on the strength and composition of Ceres' crust and its deeper interior after studying the planet's topography.
The study found that a weak crust which is composed of ice and salts have better chances to deform over time than a strong, rock-dominated crust in the solar system.
Fu's team found that the Ceres' surface would be made of a mixture of ice, salts, rock, and components similar to clathrate hydrate. The clathrate hydrates are composed of water molecules which are surrounded by gas molecules. A structure of this form could be 100 to 1000 times stronger than water ice while having the same density.
The researchers believe that the Ceres had more prominent surface features which were smoothened out over time. They believe that the flattening of mountains and valleys would be resultant of liquids.
The researchers believe that the ice, clathrate hydrates and salts were frozen from the ancient ocean. They believe that the ocean has not been completely frozen yet as it would be still existing below the frozen surface. The results of the Dawn mission give more evidence for this finding.
Meanwhile, this discovery has given more strength to the predictions made by the American Astronomy Society Division for Planetary Science which claimed that highly advanced civilizations of other planets may not be able to contact humans because of the disconnect between signals. This theory, which is named as 'Fermi paradox' says that life would be existing in ocean worlds which are separated from its surface by ice layers.
The Dawn mission has earlier discovered the possible presence of organic materials in Ceres. Maria Cristina De Sanctis, of the National Institute of Astrophysics, Rome had stated that "This is the first clear detection of organic molecules from orbit on a main belt body."