- Attachment: Comet
- When an icy comet is in space its water ice cannot turn into a liquid. If it gets nearer to the Sun its ice turns to water vapor directly in a process called sublimation. When this occurs the comet forms a tail of vapor and dust pointing away from the Sun.
- Asteroids are objects that are chunks of rock, no ice. Asteroids vary in size from several feet wide to 600 miles wide. Asteroids are pieces of rock in the inner Solar System that never formed into planets. They are leftover orbiting debris in between the planet orbits. Most exist between the orbits of Mars and Jupiter in what is called the Asteroid Belt. Most all the meteorites that hit the Earth are this asteroid debris.
- Categorizing has its limits and there are some surprises. For example: astronomers were studying a particular asteroid 7968 , named Elst-Pizarro, as its elliptical orbit inside the Asteroid Belt became closest to the Sun. When it reached a closer orbit it formed a tail. Asteroids are not supposed to form tails. Is this a misplaced comet? What’s going on?
- The Elst-Pizarro’s tail was changing structure and brightness over the 5 months it was being observed. It was spinning rapidly completing one rotation every 3.5 hours. The tail was composed of dust particles so small and fine they were more like smoke. Maybe the asteroid suffered a collision and the impact released dust and water ice from deep inside? Or, maybe this was just a comet that happened to get flung inside the orbit of Jupiter.
- My personal explanation is that the Universe is not black and white. The categorizing needs to make room for hybrid objects. Some objects formed at the margins could be half comet and half asteroid. Half rock and half ice. Astronomers try to figure this out by getting a “signature” of the proportions of the various elements found in the comet tails.
- An example used for a signature would be the ratio of heavy hydrogen to normal hydrogen. Heavy hydrogen is an isotope of hydrogen that has a neutron and is called Deuterium. Most comet tails had ratios that were rich in Deuterium and did not match the ratios found in the oceans on Earth. Because these signatures to date were such a bad match to our water it was unlikely that comets were the source of Earth’s water. When the planet Earth first formed it was so hot all the water would have vaporized and evaporated into outer space. Something had to have delivered the water after the planet had cooled down.
- A recent space probe discovered new data. The comet Hartley 2 residing in the Asteroid Belt had 50% the amount of heavy hydrogen of other comets. Its water signature closely matched that found in Earth’s oceans. Could these comets have been the source of Earth’s water.
- Let’s say during the early evolution of the planet, but a billion years after it was formed and cooled down, we were bombarded by showers of comet meteorites. Between 3,800,000,000 and 4,200,000,000 years ago a range of comets hit the planet. Comets that were smaller, say 2 kilometers wide landed every six months. Bigger comets that were 20 kilometers wide impacted every 600 years. Then there were a few really big comets, say 200 kilometers wide that impacted with devastation every 1,000,000 years. These were all balls of ice. Would they have been the source of the Ocean’s water?
- Today the Earth contains 1,330,000,000 cubic kilometers of liquid water. Ice expands and is 6 times the volume of liquid water. Could the ice balls of comets have enough water to fill the oceans?
- First calculate the volume of the 3 sizes of comets, Volume = 4/3 * pi * radius^3
----------- The volumes would be: 4.2 km^3, 4,200 km^3 , and, 4,200,000 km^3
- If these comets were delivering ice we would need 6 times ( 1.33 *10^9 km^3)
------------------ We need 8*10^9 km^3 of ice.
- If the comet storm hitting the Earth lasted 400,000,000 years we would need an average of 20 km^3 of ice delivered each year.
- Calculate the average ice delivery for each size comet per year:
----------------- 4.2 km^3 / 6 months = 8.4 km^3 / year
----------------- 4,200 / 600 = 7.0 km^3 / year
----------------- 4,200,000 / 1,000,000 = 4.2 km^3 / year
- This bombardment of comets does give us an average 20 km^3 of ice / year.
We need 8*10^9 km^3 of ice to fill the Earth’s oceans and if we received 20 km^/ year for 400,000,000 years that would do the job. The math works. The physics works with the comet tail signature match. Water on the Earth likely came from Kuiper Belt comets getting flung out of their orbits by the immense gravity of Jupiter at bombardment Earth for 400,000,000 years. The next time you look out over the ocean an new image might come to mind. A shooting star that turns out to be a giant ice ball splashing into the Earth. So we think.
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707-536-3272, Thursday, November 24, 2011
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