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-------------------- 2590 - CERES - dwarf planet?
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- The 5th planet to be discovered in 1801 was “Ceres“. It got demoted to an asteroid in 1850 because it is only 600 miles across, too small for a planet. Then, it got promoted to a Dwarf Planet because larger “ dwarf planets” were discovered beyond Pluto, beyond Neptune, in the Oort Cloud of comets. Some are larger than Pluto, that is 1,440 miles diameter.
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- The Dawn spacecraft was launched in 2007. It visited the asteroid Vesta in 2011 and 2012 (See separate reviews about this exploration.). Dawn arrived in Ceres in 2015.
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- Dawn entered its orbit of Ceres March 16, 2015 carrying a camera with 8 filters in front of a CCD. Seven of the filters collect a narrow range of wavelengths at 430 nanometers (deep blue color) to 980 nanometers ( near infrared ). There are 4 spectrometers that operate from 0.4 to 1.0 microns ( 400 to 1000 nanometers ) to measure the light intensity at the different wavelengths. Two other spectrometers measure Gamma Rays and Neutrons that are kicked up from Cosmic Rays hitting the surface.
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- What these spectrometers discovered was large deposits of water-ice near the surface. Some water molecules were in cold, dark craters, with temperatures of -260 F. Other water ice was likely locked in a form of porous rocky materials on the surface. Ceres is a rocky body that holds 20 to 30 percent water.
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- Ancient cryo-volcanism is evidenced where water vapor has exploded through the crust from subsurface aquifers. They have identified 21 cryo-volcanic domes ranging from 0 to 53 miles across. The largest has an altitude of 13,000 feet above he surface.
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- The spectrometers detected hydrogen, iron, and potassium in the surface crust. Hydrogen levels were almost 10% of the composition by weight. There were also concentrations of iron and carbon. This has lead to the theory that the decay of radioactive elements created enough heat to cause the planet’s structure to differentiate between a rocky interior and an icy outer shell.
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- Ice separated from rock early in Ceres’ history forming an ice-rich crusted layer. Where this water came from remains mystery. Was it formed with the planet , or, was water deposited by meteors? The later scenario is believed to be how water arrived on the planet Earth.
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- When the water sublimated, evaporated from the surface, it left behind the dissolved salts. These are highly reflective, bluish areas found in over 130 locations on the surface.
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- Ceres is 588 miles in diameter and has a surface area 35% the size of the contiguous United States. Or, abut 1/3 the size of our Moon. Its overall density is 2.2 grams per cubic centimeter. Dry rock is 3.4 gm/cm^3. This lower density suggests that water is a major constituent. ( water is 1.0 gm/cm^3 )
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- The conclusions are that Ceres is a watery and geologically active proto-planet. And, it could hold clues of how life existed billions of years ago?
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- Ceres has fewer large craters than expected. None are larger than 175 miles across. Only 16 are larger than 62 miles. The theory is that the larger craters have been erased due to deep subsurface ice-rich layer of material causing the crater rims to relax and become invisible.
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- Ammonia is a molecule consisting of nitrogen and oxygen. It would have not condensed in the rock, it would have evaporated, If Ceres was always in its current location. Likely, Ceres formed in the outer Solar System beyond Saturn then later migrated to its current orbit.
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- Vesta , on the other hand, is dry and rocky, more like the stony terrestrial planets closer to the Sun.
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- The Dawn spacecraft has photographed 90% of the Ceres surface down to an altitude of 240 miles. At higher elevations, 4,500 miles, Dawn is measuring the intensity of Cosmic Rays.
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- Ceres was first discovered in 1801 by Giuseppe Piazzi. It was given the name asteroid which in Greek means “starlike”.
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- Still more to learn. May you live in interesting times. An announcement will be made shortly, stay tuned. Other reviews available on this subject:
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- 1860 - The Dawn spacecraft will orbit Ceres for another 50 years before crashing into its surface.
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- 1618 and 1572 Dawn spacecraft visit’s the asteroid Vesta.
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- 1784 - Ceres has a crater that is 175 miles across and 9 miles deep.
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- 847 - Ceres orbit’s the Sun in 4.6 years at a distance of 2.77 astronomical units.
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- January 20, 2020 1911 2590
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--------------------- Monday, January 20, 2020 --------------------
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