Dawn approaches to Ceres
This dwarf planet is the largest object in the asteroid belt between Mars and Jupiter and is also one of the most enigmatic. Among the objectives of the NASA probe, one is to investigate the role of water in the early stages of the primordial Solar System.
Lacking a little over three months, NASA’s Dawn will orbit the dwarf planet Ceres, which, with a diameter of 950 km, is the most massive asteroid main belt of the solar system between Mars and Jupiter (where there is also Vesta, another potential protoplanets as Pallas and Igea).
In comparison, Vesta has a diameter of 525 kilometers and it is the second massive body in the belt. The Dawn spacecraft, launched in 2007, has recently entered into the so-called phase approaching and pointing straight towards the only minor body of our system to be considered – so far – a dwarf planet, like Pluto. The fateful meeting will take place on March 6 and the probe will orbit Ceres for about a year.
It is a mission of NASA’s Discovery Program: the satellite reached its first target, the asteroid Vesta, in 2011. After 14 months in orbit around Vesta, the probe was set in motion to reach Ceres. The mission is the first to reach and orbit two different celestial bodies and the INAF has an important role, being responsible for the imaging spectrometer VIR (Visual and Infrared Spectrometer) in the visible and near infrared. “The imaging spectrometer VIR is funded by ASI and was built entirely in Italy,” says Maria Cristina De Sanctis, a researcher at the Institute of Astrophysics and Space Planetology in Rome. “Italy contributes to the operations of the probe and participates in the mission with several co-investigators and team members.” She added: “The dwarf planet Ceres is an object still very enigmatic and presents researchers with many questions, including the origin of the water vapor transient observed recently. One of the objectives of Dawn is investigating the role of water in the early stages of the primordial solar system and Ceres is the key to this goal. ”
Recently Dawn is output from the phase of solar conjunction, where he was on the opposite side of the Sun from the Earth, which has limited communications. The satellite is currently at 640.000 km from Ceres and traveling at a speed of 725 km / h. “Ceres is almost a mystery to us,” said Christopher Russell, principal investigator of the Dawn mission from the University of California. “Ceres, unlike Vesta, has no meteorites that orbit it which could help us to reveal its secrets. All we can predict with certainty is that we will be surprised, “he added.
Scientists believe that Ceres and Vesta are very different: the first may have formed later than Vesta and could have an icy nucleus. The evidence collected in recent years suggest that Vesta has maintained only a small amount of water it would be formed when the radioactive material was more abundant, which would produce more heat. Ceres, on the contrary, has a thick mantle of ice and it is said that it has an ocean beneath its crust. The De Sanctis explained that “Vesta is an object basaltic, relatively free of material rich in water, which is differentiated before the Earth; Ceres is an object rich materials hydrates, probably differentiated, but with an evolutionary history completely different from that of Vesta. These two objects are so different but placed in the same area of the solar system will show us the evolutionary processes that have been at the origin of the solar system that we see today. ”
The probe uses the ion propulsion, and to travel in deep space is considered more efficient than chemical propulsion. Why? In an ion engine, the charged particles (ions), after being are accelerated by an electric field, are channeled into the space through a nozzle. Using the principle of action and reaction the spacecraft gets a little push in the opposite direction. The mission Dwan has just completed five years of propulsion, far more than any other spacecraft.
By the end of January will come the images sent from the spacecraft and the data will be the best ever obtained of the dwarf planet Ceres.