Dwarf Planet Ceres
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Researchers have shed new light on the dwarf planet Ceres, which lies in the asteroid belt between Mars and Jupiter and is also the largest object in that belt.
Ceres now has the status of an “ocean world”, after scientists analysed data collected by NASA’s Dawn spacecraft.
What is a ‘dwarf planet’?
- As of today, there are officially five dwarf planets in our Solar System. The most famous is Pluto, downgraded from the status of a planet in 2006. The other four, in order of size, are Eris, Makemake, Haumea and Ceres. The sixth claimant for a dwarf planet is Hygiea, which so far has been taken to be an asteroid.
- Last year, using observations made through the European Space Organisation’s SPHERE instrument at the Very Large Telescope (VLT), astronomers found that Hygiea may possibly be a dwarf planet since it satisfied the four criteria set by the International Astronomical Union (IAU) for a celestial body to be called a dwarf planet.
Criteria for a dwarf plant
- These four criteria are – that the body orbits around the Sun, it is not a moon, has not cleared the neighbourhood around its orbit (which means it is not the dominant body in its orbit around the Sun and this is what differentiates a planet from a dwarf planet) and has enough mass for its gravity to pull it into a roughly spherical shape.
- Ceres is the largest object in the main asteroid belt that lies between the orbits of Mars and Jupiter.
- The dwarf planet was first spotted by Giuseppe Piazzi in 1801, who assumed that Ceres was the missing planet between Mars and Jupiter.
- It was classified as a dwarf planet in 2006 and is the first dwarf planet to be orbited by a spacecraft.
- In 2015, NASA’s Dawn reached it to study its surface, composition and history.
- Dawn was launched in 2007 and visited Vesta and Ceres.
- In 2015, it went into the orbit around Ceres and the information it collected reinforced the idea that dwarf planets could have hosted oceans over a significant part of their history. The mission concluded in 2018.
What does it mean to be an ‘ocean world’?
- Ceres, NASA has said, “is a crucial piece of the ocean worlds puzzle”. “With a crust that mixes ice, salts, rock-forming minerals and other materials, Ceres looks to be a remnant “ocean world,” wearing the chemistry of its old ocean and records of the interaction on its surface.” Scientists are interested in exploring ocean worlds because they may support life.
- The observations from Dawn suggest the presence of briny liquid water under Ceres’s surface. Before the mission ended in October 2018, the spacecraft dipped to less than 35 km above the surface of the dwarf planet, due to which it was able to collect data in a higher resolution.
- Now, by analysing this data, which was collected at the end of the mission, scientists have determined that Ceres has a brine reservoir located about 40 km deep and which is hundreds of miles wide, making the dwarf planet, “water rich”.
- There are other dwarf planets and moons in our solar system where oceans exist, including the moons of Saturn and Jupiter.