Bright Spots on Ceres

I have previously posted about asteroid/dwarf planet Ceres before. The Dawn Spacecraft recently arrived at Ceres and began a comprehensive study of the dwarf planet that has never been done before. One of the strange things that Dawn found on Ceres were bright spots that confounded scientists at first. What were they?

Via NASA/Dawn

 

The bright spots were discovered in a crater now known as Occator, an 80-km diameter crater at 19.5° latitude on Ceres. They are called faculae which means “bright spots”. Faculae are more commonly known as the bright regions on the Sun surrounding a sunspot. Where do the faculae on Ceres come from?





One theory is that they are ice spots in the crater that are reflecting sunlight or salt deposits left over after salty water on the surface evaporated away. These spots might have come from Ceres actually having a dusty surface, and minor impacts on the surface exposed the underlying ice or salt.



Another theory, which is more widely accepted, is that the spots are actually ice geysers or cryovolcanoes (volcanoes that spew ice rather than lava). This is believed to be the true cause as Dawn has seen haze above the spots.





We will probably learn more as Dawn continues its reconnaissance around Ceres. And if these are ice features, Ceres could be a great place to build a future way station in the Solar System.

 

NASA's Dawn Spacecraft

NASA is on the verge of visiting an asteroid. The Dawn spacecraft is about as far from Ceres as the Moon is from Earth right now and is beginning to send back images of the asteroid. The resolution is not as good as Hubble (yet), but as it gets closer, we will begin to see it in better detail.

This processed image, taken Jan. 13, 2015, shows the dwarf planet Ceres as seen from the Dawn spacecraft. The image hints at craters on the surface of Ceres. Dawn's framing camera took this image at 238,000 miles from Ceres. (NASA/JPL-Caltech/UCLA/MPS/DLR/IDA)

There are a couple of places that you can follow the Dawn Program.

• Twitter: NASA_Dawn
• NASA's Dawn Homepage

1 Ceres

NASA's Solar System Explorations Page



Ceres was the first asteroid discovered in the Asteroid Belt on 1 January 1801 by Giuseppe Piazzi. When he first discovered it, he thought it was a planet, as it was a common belief at the time that there might be a planet between Mars and Jupiter because of the large gap between the two planets.
Because there was not enough information to determine the orbit of Ceres, it wasn't confirmed to exist until December of 1801. After close observation of Ceres, it was determined that it was not a planet, but something new. It was then that William Herschel coined the term "asteroid" as the object had a star-like appearance so was difficult to distinguish from the background stars. However, after observing Ceres and other asteroids over the course of days and weeks, it was apparent that asteroids move faster in the sky than the stars since they are much closer to Earth.

Ceres is small compared to the planets and many satellites, but it is the largest object in the Asteroid Belt by a wide margin. 

• It has a diameter of about 950 km or the size of Texas
• It's mass is 9.47x10²° kg, or about 0.00016% of the Earth. Despite its mass, Ceres contains 25% of all the mass in the Asteroid Belt
• It has a semi-major axis (orbital radius) of 2.76 AU

As shown in the opening picture, Ceres is relative spherical. Much like the planets, is an oblate spheroid with a wider diameter at the equator than the poles. This shows that it rotates on an axis uniformly. Other asteroids with irregular shapes kinda tumble and wobble in space as they rotate.

We've learned more about Ceres as telescopic observations became more sophisticated and advanced. Ceres does not fit into the three main types of asteroids mentioned in the previous post. In fact, like planets, it is differentiated (layered) with a rocky core, an icy mantel, and an outer crust.

NASA's Solar System Explorations Page

For the next two centuries, Ceres was still considered an asteroid as there was no other category of object it fit in. It's official designation was 1 Ceres as it was the first asteroid discovered and Ceres is its proper name. However, in 2006 when Pluto was demoted from planet status to minor planet, it was concluded that Ceres should be upgraded. Ceres is now officially considered a dwarf planet. It is too small to be a planet (and where the lower limit to be considered a planet is still murky) but too large and too regularly shaped to be an asteroid.

One final weird thing discovered on Ceres is that it is slightly active. An object as small as Ceres should not have any sort of eruptions going on, but in January of 2014, the Herschel Space Telescope discovered water vapor plumes emitted from the surface. We will learn more about Ceres in the coming years when the space probe Dawn arrives at Ceres and begins its exploration. Ceres is also the third most likely spot for crewed missions to visit after the Moon and Mars.