The largest known asteroid may contain more water than Earth and look like our planet in other ways, according to research that blurs the line between planets and asteroids.
Michal Levinstein, Israel Astronomical Society
The largest known asteroid may contain more water than Earth and look like our planet in other ways, according to research that blurs the line between planets and asteroids.
Astronomers took 267 images of the asteroid Ceres with the Hubble Space Telescope. From these images and subsequent computer simulations, they suggest that the asteroid Ceres has a rocky core and a thin outer crust of dust.
A group led by Peter Thomas from Cornell University in the USA says that Ceres is almost spherical - which proves that gravity controls its shape. Also, the non-uniform shape of the asteroid proves that the material is not uniformly distributed inside it.
These and new clues, which also include a low density of Ceres - point to an interior full of icy water - say the astronomers.
big and round
Ceres has long been considered one of the tens of thousands of asteroids that inhabit the asteroid belt between Mars and Jupiter. With a diameter of 580 miles (930 km) – about the size of the US state of Texas – it is the largest asteroid in the asteroid belt and about 25% of its mass.
Astronomers thought Ceres never got hot enough to form layers of matter.
But computer models now suggest that Ceres has a different face - compressed material in the core and light material in the shell. Possible configurations include an ice-rich mantle made of water surrounding a rocky core. If this shell consists of at least 25% water - Ceres may contain more water than Earth - according to statements from the Space Telescope Science Institute, which operates the Hubble Space Telescope for NASA and the European Space Agency.
According to the most possible scenario from the knowledge we have about the formation of other objects - Ceres has a rocky core and a mantle. The mantle is probably made of a mixture of ice (made of water) with dust and other ingredients. "The mantle can be as much as 1/4 of the entire object," says study author Joel Parker of the Southwest Research Institute. "Even though it's a small object compared to Earth - it may contain a larger amount of water."
On Earth, the water forms a thin layer a few miles thick in some places and less than that in others. The layer of water proposed for Ceres - which is much smaller - is many miles thick.
"The total volume of water on Earth is approximately 1.4 billion cubic kilometers - of which 41 million cubic kilometers are fresh water. If the mantle of Ceres is indeed 25% of its mass - this would translate to 200 million cubic kilometers of water," says Parker.
An embryonic world
Other researchers recently announced the discovery of 2003 UB313 – a round object in our solar system – 1/3 times larger than Pluto and 2,100 times farther from the Sun. But even an object of this size - 4 miles in diameter, which is almost XNUMX times that of Ceres - is not officially certified as a planet.
Astronomer Brian Marsden Brian Marsden - who runs the Minor Planet Center which collects data on small bodies - says that if Pluto is considered a planet, other round bodies may also be considered planets. Under this definition shared by other astronomers - Ceres, 2003 UB313 and a handful of other large bodies can be called planets. The alternative - they claim - is to stop calling Pluto a planet.
Another explanation is that Ceres is a kind of "baby" planet - an undeveloped version of Earth and other rocky planets. According to this view, Ceres appears as young planets looked 4 billion years ago.
The leading theory of planet formation holds that small rocks collided with each other, stuck together and gradually grew. Depending on location and orbit - a developing world may or may not encounter enough raw material to grow and become like the 4 traditional rocky planets.
"Ceres is an embryonic world," says Lucy McFadden, a member of the observation team at the Department of Astronomy at the University of Maryland, USA. Gravitational deviations from Jupiter billions of years ago prevented Ceres from collecting enough material to become a real planet."
In 2015, scientists will get a closer look at Ceres, when NASA's Dawn Mission orbits the asteroid. Such a look may provide additional clues about its composition.
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For information on the Universe Today website
For news on the subject at Space.com
