Starship Asterisk*

Centauri Dreams wrote:Getting water into the inner Solar System is an interesting exercise. There has to be a mechanism for it, because the early Earth formed at temperatures that would have caused any available water to have evaporated. Scientists have long speculated that water must have been delivered either through comets or asteroids once the Earth had cooled enough to allow liquid water to exist. The former was preferred because the water content in comets is so much higher than in asteroids.

But the theory had problems, not the least of which was that comets studied in this regard showed deuterium levels twice that of Earth’s oceans. The ratio of deuterium and hydrogen, both made just after the Big Bang, can vary in water depending on its location because local conditions can affect the chemical reactions that go into making ice in space. A comparison of the deuterium to hydrogen ratio in extraterrestrial objects can be compared to water found in Earth’s oceans to identify the source of our water. Now comet Hartley 2 swings into the picture, for researchers have announced that its hydrogen/deuterium ratio is similar to Earth’s oceans.
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Remember, previous comet studies had found hydrogen/deuterium ratios different from our oceans. The difference between these comets and Hartley 2 may be that Hartley 2 was formed in the Kuiper Belt, whereas other comets studied in this regard are thought to have first formed near Jupiter and Saturn before being flung out by the gravitational effects of the gas giants, returning millions of years later for their pass around the Sun. The hydrogen/deuterium ratio we see in water ice may well have been different in the Kuiper Belt than in ice that first formed in the inner system, where conditions are much warmer. Further comets studies may confirm the idea.
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Surely the early oceans were the result of both comet and asteroid impacts, but the new findings point back to comets as major players. Even so, we have plenty of work to do to understand the role of the lightest elements and their isotopes in the early Solar System. Six comets besides Hartley 2 have been examined for hydrogen/deuterium levels, all with deuterium levels approximately twice that found in Earth water. Kuiper Belt comets were once thought to have even higher deuterium levels than Oort Cloud comets, an idea the Hartley 2 results have now refuted.
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Ann wrote:....found a claim,
....the same source,
Also, this same source

Indigo_Sunrise wrote:And bystander - LOVE the new avatar!

owlice wrote:He might be wondering that, too!

casuspacem wrote:
"Since the ratio of deuterium is related to the solar system environment where the comet formed, the Herschel results indicate that Kuiper Belt comets could have contributed substantial amounts of water to Earth's oceans."

----"In the six hundredth year of Noah's life, in the second month, on the seventeenth day of the month, on that day all the fountains of the great deep burst forth, and the windows of the heavens were opened." Gen 7:11

Indigo_Sunrise wrote:

Ann wrote:....found a claim,
....the same source,
Also, this same source

Ann, can you share your source/s via a link, perhaps? (Of course, if it's something you merely 'searched' for, can you let us know that, also?)


Star clusters really intrigue me, and this image is a double bonus - with green-tinged Comet Hartley 2 (103/P Hartley)floating through.
Excellent image!

LMartin wrote:
It's going to Kuiper belt and back here in 6 yrs?

neufer wrote:At the time the animals came in the form of Methane

Booster wrote:
The oceans are big. Really big. And really, really deep. I find it hard to believe that all of that water came from comet impacts. And if they did, wouldn't comets of that mass cause planetary deformation sufficient to have reheated its surface to vaporizing temperatures again?

• The total mass of Eris is about 16.7×10²¹ kg.
  
  The total mass of Pluto is about 13.1×10²¹ kg.
  
  The total mass of Charon is about 1.5×10²¹ kg.
  
  The total mass of [Earth's] hydrosphere is about 1.4×10²¹ kg

http://en.wikipedia.org/wiki/Moon#Formation wrote:
<<The prevailing hypothesis today is that the Earth–Moon system formed as a result of a giant impact: a Mars-sized body hit the nearly formed proto-Earth, blasting material into orbit around the proto-Earth, which accreted to form the Moon. Giant impacts are thought to have been common in the early Solar System. Computer simulations modelling a giant impact are consistent with measurements of the angular momentum of the Earth–Moon system, and the small size of the lunar core; they also show that most of the Moon came from the impactor, not from the proto-Earth. However, meteorites show that other inner Solar System bodies such as Mars and Vesta have very different oxygen and tungsten isotopic compositions to the Earth, while the Earth and Moon have near-identical isotopic compositions. Post-impact mixing of the vaporized material between the forming Earth and Moon could have equalized their isotopic compositions, although this is debated. The large amount of energy released in the giant impact event and the subsequent reaccretion of material in Earth orbit would have melted the outer shell of the Earth, forming a magma ocean.>>

Booster wrote:The oceans are big. Really big. And really, really deep. I find it hard to believe that all of that water came from comet impacts. And if they did, wouldn't comets of that mass cause planetary deformation sufficient to have reheated its surface to vaporizing temperatures again?

Red Lord of Mars wrote:I wanted to ask if the small formation in the lower left corner of the pic is the Cat's Eye Nebula...