- 1696 - Comet landing with Rosetta mission is collecting science that tells us a history of our planet. Did comets bring water to Earth 4 billion years ago?
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--------------------------- 1696 - Comet - Rosetta after Landing
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- See Reviews # 1692 and #1688 for an introduction to the Rosetta mission landing on a comet, November, 2014. This review begins the story of what we are learning from this adventure.
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- “ Philae”, the Lander sent 64 hours of data before its batteries went dead and the instruments shut down in hibernation. November 12, 2014 the landing occurred on a comet 2.5 miles in diameter traveling at 37,300 miles per hour. This all happened 319,000,000 miles away from Earth between Mars and Jupiter.
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- The batteries drained because the Lander bounced to a site almost devoid of sunlight making its solar panels inoperable.
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- Ten instruments on board the Lander were still able to transmit their data. The landing itself was a tricky maneuver. The Lander weighing 100 kilograms on Earth ( 220 pounds) weighs only 1 gram on the comet. No wonder the Lander bounced leaping 3,200 feet above the surface ( 0.6 miles). The surface below was rotating. Where it eventually landed gets only 1.5 hours of sunlight. The Sun is too far away and that is too short a time for the feeble sunlight to recharge the batteries.
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- A second attempt will be made when the comets gets closer to the Sun and the Lander comes out of hibernation.
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- Pictures showed the landing site to b a dusty surface covered in rock-like material having a wide range of sizes. A hammer mechanism on a 40 centimeter rod ( 16 inches ) probed the surface. The dust was 4 to 8 inches thick. Below that was rock hard ice. With the previously calculated low density of the comet the ice was expected to be porous. Not so at this landing, it was unusually hard ice.
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- A magnetometer measured the comet’s magnetic field. Samples were taken from the surface identifying organic molecules. Water H2O, carbon monoxide CO, carbon dioxide CO2, ammonia NH3, Methane CH4, methanol CH4O. Analytical chemist are busy pouring over this data to learn if chemical signatures are similar to those found on the Earth. Are their amino acids and water that could support life?
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- In August 2015 the comet will be at its closet point to the Sun. Attempts will be made to wake up the Lander to resume tests. In the meantime Rosetta the Orbiter will continue to operate and make its own observations.
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- One achievement completed when the Lander was operating involved the Orbiter from the opposite side of the comet passed a radio signal through the comet to the Lander. This analysis will be similar to a CAT Scan that will create a 3-D image cross sections of the comet.
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- Review # 1692 calculates the comet’s volume assuming that it is approximately two spheres connected together. One is 2.4 kilometers in diameter, the other is 0.8 kilometers diameter. The volume calculates to be 9.4*10^2 meters^3 , the mass 2.8 *10^12 kilograms ( 2.8 billion tons ), the density 300 kilograms / meter^3. Water is 1,000 kilograms/ meter^3.
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- More sophisticated calculations use the volume of the large lobe 2.5 x 2 x 0.8 miles and the small lobe 1.6 x 1.6 x 1.2 miles with a density of 400 kilograms / meter^3. The Earth’s density is 14 times greater at 5,600 kilograms / meter^3
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- One of the mysteries Rosetta hopes to solve is how water arrived on Earth. We know that the Earth’s early formation was too hot for liquid water to survive. Somehow water had to arrive after the Earth cooled down. The bombardment of comets in the early days of the Solar System may have been the delivery mechanism.
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- By analyzing the isotopes in the water and the “ chirality” of the molecules, were they left-handed or right-handed molecules, ( Earth molecules are left-handed) science can determine if there is a match. The abundance of the Deuterium isotope in Earth’s water is 0.015%. If comet water is the same ratio there would be another match. Well, then we can thank the comets for life on Earth.
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- Comet bombardment occurred 4 billion years ago. estimates have been made that in over 400 million years the ice that was deposited could have filled the Earth’s oceans.
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----------------------- 2 kilometer diameter comets hit every 6 months, on average
----------------------- 20 kilometer comets hit every 600 years
----------------------- 200 kilometer comets hit every 1,000,000 years
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- The volume of ice in comets this size is V = 4/3 *pi*r^2:
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----------------------- 2 kilometer comets , V = 4.2 kilometers^3
----------------------- 20 kilometer comets , V = 4,200 kilometers^3
----------------------- 200 kilometer comets , V = 4,200,000 kilometers^3
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- The volume of ice delivered per year is 20 kilometers^3:
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-------------------- 4.2 kilometers / 0.5 years = 8.4 kilometers^3/ year
------------------- 4,200 kilometers^3 / 600 years = 7.0 kilometers^3/ year
------------------- 4,200,000 kilometers^3 / 1,000,000 years = 4.2 kilometers^3 / year
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- Solid ice is 6 times the volume of liquid water.
- So, the total volume of water delivered is 3.33 kilometer^3 / year.
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- The water in Earth’s oceans totals 1.33 billion kilometers^3
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------------------------- 1,330 * 10^6 / 3.33 = 400 * 10^6 years
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- Therefore, if this much ice landed on the surface of the Earth over 400 million years that could account for all the water in Earth’s oceans.
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- Stay tuned, there is much more to learn on this Rosetta adventure.
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- Other Reviews about comets available upon request:
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- # 1623 Calculate the amount of water lost by a comet as it loops around the Sun.
- # 1612 How many comets make close flybys to Earth?
- # 1600 Comet ISON November 2013
- # 1338 Did comets bring water to Earth?
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RSVP, with comments, suggestions, corrections. Index of reviews available ---
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