History
Ceres is the only dwarf
planet in the inner solar system and the largest object in the asteroid belt
between Mars and Jupiter. When Giuseppe Piazzi discovered it in 1801, it was
the first member of the asteroid belt to be discovered. Ceres became the first
dwarf planet to have a spacecraft visit when Dawn arrived in 2015.
Ceres was previously
classed as an asteroid, but astronomers classified it as a dwarf planet in 2006
because it is so much larger and different from its rocky neighbor’s. Even
though Ceres makes up 25% of the overall mass of the asteroid belt, Pluto is 14
times more massive.
Ceres is named after
Ceres, the Roman god of corn and harvests. The word cereal is derived from the
same word.
Size & Distance
Ceres is 1/13 the
radius of Earth, with a radius of 296 miles (476 kilometers). Ceres would be
around the size of a poppy seed if Earth were the size of a nickel. Ceres is 2.8
astronomical units distant from the sun, at a distance of 257 million miles
(413 million kilometers). The distance
between the sun and Earth is measured in astronomical units (abbreviated as
AU). It takes 22 minutes for sunlight to get from the sun to Ceres at this
distance.
Figure 1 Ceres is a dwarf planet located between Mars and Jupiter in the main asteroid belt. Credits: NASA's Visualization Technology Applications and Development department (VTAD).
Rotation
Ceres completes one
orbit around the sun every 1,682 Earth days (4.6 Earth years). Ceres' day is
one of the shortest in the solar system because it rotates once every 9 hours. Ceres' rotation axis is only 4 degrees off the plane of its orbit around the sun. This
implies it rotates nearly completely upright and has no seasons like other
planets with more tilted orbits.
Formation
Ceres formed around 4.5
billion years ago, along with the rest of the solar system, when gravity drew
spinning gas and dust in to create a small dwarf planet. Ceres is classified as
an "embryonic planet," meaning it began to form but did not fully
develop. Jupiter's powerful gravity kept it from becoming a complete
planet. Ceres landed into its current location in the asteroid belt between
Mars and Jupiter around 4 billion years ago, among the remaining parts of
planetary creation.
Structure
Ceres is closer to the
terrestrial planets than its asteroid companions (Mercury, Venus, Earth, and
Mars), yet it is far less dense. Ceres' layers aren't as well defined as those
of Ceres. Ceres is thought to have a solid core and a water-ice mantle. Ceres
could have a water content of up to 25%. Ceres has more water than Earth if
this is right. Ceres' crust is rough, dusty, and covered with massive salt
deposits. The salts on Ceres aren't like table salt (sodium chloride) but are
made up of a variety of minerals such as magnesium sulphate.
Surface
Ceres has a plethora of
small, new craters, none of which are greater than 175 miles (280 kilometers)
in diameter. Given that the dwarf planet must have been hit by multiple massive
asteroids during its 4.5 billion-year existence, this is astonishing. It's possible that the
lack of craters is due to ice layers beneath the surface. If ice or another
lower-density material, such as salt, is present near the surface, the surface
characteristics may smooth out with time. Some enormous craters may have been
obliterated by prior hydrothermal activity, such as ice volcanoes. There are areas in some
of Ceres' craters that are always in shadow. These "cold traps" could
have water freeze in them for long periods of time if they aren't exposed to
direct sunshine.
Figure 2 Occator Crater, which is 57 miles (92 kilometers) broad and 2.5 miles (4 kilometers) deep and contains Ceres' brightest section, is depicted in this generated perspective image. NASA/JPL Caltech/UCLA/MPS/DLR/IDA/NASA/JPL Caltech/UCLA/MPS/DLR/IDA/NASA/JPL-Caltech/UC
Atmosphere
Ceres' atmosphere is
extremely thin, and there is evidence that it includes water vapor. Ice
volcanoes or sublimating ice near the surface could produce vapors (transforming
from solid to gas).
Figure 3 Many landslides on Ceres have been discovered by NASA's Dawn satellite, which geologists believe were formed by a considerable amount of water ice. NASA/JPL Caltech/UCLA/MPS/DLR/IDA/NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/NASA/JPL-Caltech/UC
Existence of Life
Ceres is one of the few
planets in our solar system where scientists hope to find evidence of life.
Ceres possesses something that few other planets do: water. Water is necessary
for life on Earth, thus it's plausible that life may exist there provided this
and a few other conditions are met. If there are any living organisms on Ceres,
they will most likely be very minute germs akin to bacteria. While Ceres may
not have any living things today, there may be evidence that it had in the
past.
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