Ceres is the Asteroid belt’s largest object, making up around one third of the total mass or the entire belt. This dwarf planet is the largest remnant of what could have been a planet, had Jupiter not torn it apart with its massive tidal forces. Nevertheless, Ceres is still an immensely interesting object, due to the large amount of water present there, some of which could still be in a liquid state according to a recent paper.
Ceres is quite small for a planet, spanning just 950 km in diameter (about the size of Texas). Large parts of it is covered in water ice. In fact, Ceres is thought to hold more water than any inner solar system planet, apart from our Earth.
This large amount of water, comparable in volume to to Utah’s Great Salt Lake, has been detectable by scientists with ground-based telescopes for a while now. However, it took the act of sending a spacecraft to the dwarf planet to discover that parts of this water were still liquid.
What did NASA’s Dawn spacecraft find on Ceres?
The water was discovered by the Dawn spacecraft in 2018 when it did a fly by. There photos of craters surrounded by blueish looking material could be seen. Now, after much research, scientists suggest that this is salty ice launched into the air during an asteroid impact some 20 million years ago.
Theoretical models predicted that Ceres might once have had a liquid layer beneath its mantle, with a hydrated core. However, these same models predicted that all of this water would be frozen a long time ago. But they did not account for all possible factors, like salt.
Astronomers postulate that this is because of the high levels of salt in the water, brought there by impacts with smaller bodies. This salt lowers the freezing point of the water, and helps it remain liquid. Besides this it is thought that a compound called hydrates helps with this. Hydrates are a type of water cage that traps gas or salts without truly mixing with them. This affects the way that heat is transferred through the medium, again allowing for the water to freeze very very slowly.
Ceres now thought to be an ocean world
Following the discovery of hydrohalite near the Occator impact crater, a clear sign Ceres used to have sea water, Maria Cristina De Sanctis, from Rome’s Istituto Nazionale di Astrofisica said:
“We can now say that Ceres is a sort of ocean world, as are some of Saturn’s and Jupiter’s moons.”
The existence of these tiny oceans of course brings up the question of life on the dwarf planet, something that might be investigated in a future mission that lands on the surface and perhaps even explores the waters.
Ceres is not the only dwarf-planet with water on it. In fact, astronomers now think that this is a common feature with such bodies. The scientists behind the New-Horizons probe postulate the possibility of a similar liquid core under Pluto’s icy surface, showing once again that we still have much to learn about our solar system.