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An illustration of the Solar System, showing the asteroid belt.

The asteroid belt is between Mars and Jupiter.

An asteroid belt separates the rocky inner planets from the gaseous outer planets. But, asteroids aren’t the only objects located there. A dwarf planet called Ceres lies in that belt between Mars and Jupiter. The only dwarf planet in the inner solar system, this is the nearest dwarf planet to Earth. 

Where Does the Name Ceres Come From?

This dwarf planet is named after the Roman goddess of the harvest. An Italian astronomer, Giuseppe Piazzi, gave the dwarf planet its name after discovering it on January 1, 1801.

Planet or Asteroid?

For years, people called Ceres an asteroid. After all, it lives in the asteroid belt and isn’t nearly large enough to be considered a planet! However, it’s much larger than your average asteroid and has a more spherical shape. It is the largest body in the asteroid belt, and scientists estimate that it makes up about a third of the mass in the belt. So, in 2006, they declared it a dwarf planet.
With a width of 590 miles, Ceres is the smallest dwarf planet we currently know and has no moons. It’s the only dwarf planet in the inner solar system; the rest are near the Kuiper Belt. It’s not a full planet because it couldn’t clear the surrounding area of debris. However, it shares certain planet-like features, like its separate layers. Ceres has three layers: a rocky inner core, a 100 km-thick layer of water and ice, and a thin, dusty outer surface. 

Ceres’s Orbit

Ceres takes about 4.6 Earth years to orbit around the Sun. Although a year on the dwarf planet might be long, a day on Ceres is pretty short. One day on this dwarf planet is approximately 9 hours on Earth!

Ceres’s Bright Spots

If you look at images of this dwarf planet, you might notice some bright spots. Some of the first spots were found on a section of the planet known as the Occator Crater. This is the brightest region on the planet. Scientists believe these highly reflective spots are likely salt deposits. These deposits are mostly sodium carbonate and ammonium chloride. The presence of these salts suggests that there was perhaps an ancient ocean underneath the surface of Ceres at some point


An image of the dwarf planet Ceres.

An image of the dwarf planet’s bright spots; Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

NASA’s Dawn Mission

An artists illustration of the Dawn Spacecraft.

A 3D rendering of the Dawn spacecraft, Vesta, and Ceres

In 2007, NASA launched the Dawn Mission to study Ceres and Vesta, the largest asteroid in the belt. The Dawn became the first spacecraft to visit a dwarf planet. Since 2015, the Dawn has been gathering data on Ceres. Because of this data, we know there are traces of an ocean in Ceres’s crust. We’ve observed traces of carbonates on the surface. Carbonates are left behind when water evaporates, so we know there was likely water on Ceres.

Other Great Resources

https://www.youtube.com/watch?v=lkEUhdxWQfQ What is the Dwarf Planet Ceres? (BrainStuff – HowStuffWorks)

https://www.youtube.com/watch?v=nJiw2NxqoBU Flight Over Dwarf Planet Ceres (NASA Jet Propulsion Laboratory)

https://solarsystem.nasa.gov/planets/dwarf-planets/ceres/overview/ Ceres (NASA)

Written by: Sylvia Choo