APOD: The Comet Hartley 2 Cruise (2011 Oct 07)

[APOD Robot]

The Comet Hartley 2 Cruise

Explanation: Early last November, small but active Comet Hartley 2 (103/P Hartley) became the fifth comet imaged close-up by a spacecraft from planet Earth. Still cruising through the solar system with a 6 year orbital period, Hartley 2 is making astronomical headlines again. New Herschel Space Observatory measurements indicate that the water found in this comet's thin atmosphere or coma has the same ratio of the hydrogen isotope deuterium (in heavy water) as the oceans of our fair planet. Hartley 2 originated in the distant Kuiper Belt, a region beyond the orbit of Neptune that is a reservoir of icy cometary bodies and dwarf planets. 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. Comet Hartley 2 appears in this starry skyscape from last November sporting a tantalizing greenish coma appropriately sailing through the nautical constellation Puppis. Below the comet are open star clusters M47 (right) and M46 (left).

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[Guest]

A beautiful photo, but my attention was drawn to the oddly (orange) colored grouping of stars in the center of the photo, just below the axis of a straight line drawn between the two dominant clusters. Since I'm not all that familiar with the area,my first guess is processing artifact. Anybody want to chime in?

[Ann]

That would seem to be cluster NGC 2425. The reason for the orange color is twofold. First, the cluster is old, apparently a few billion years old, which means that the bright blue stars of the clusters have died long ago, and the brightest stars of the cluster are orange. I've also found a claim that the cluster is 3550 parsecs away, which would be more than 10,000 light-years. Whether or not the exact distance is 10,000 light-years, it is clear that the cluster is far away, and we can be sure that there is a lot of interstellar dust between us and the cluster. The dust causes reddening by scattering away blue light. NGC 2425 is undoubtedly very dust-reddened, which is the main reason why it looks so strikingly red in this image.

By comparison, the same source that puts NGC 2425 at 3550 parsecs puts M46 at 1510 parsecs and M47 at 490 parsecs. Also, this same source claims that M46 is less than a billion years old, and M47 is less than a hundred million.

Ann

[bystander]

Researchers gain new insights into Comet Hartley 2
http://asterisk.apod.com/viewtopic.php?f=31&t=23714

[nstahl]

Earth’s Oceans: A Cometary Source After All?

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.
...
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.
...
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.
...

[Indigo_Sunrise]

....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!

[Indigo_Sunrise]

And bystander - LOVE the new avatar!

[orin stepanek]

And bystander - LOVE the new avatar!

I just wonder what he'll be dressed up as tomorrow.

[owlice]

He might be wondering that, too!

[orin stepanek]

He might be wondering that, too!

Ahh! owlice; I see you're sporting a new look also.

[owlice]

Apparently so!

[neptunium]

What's yours anyway, owlice?

[casuspacem]

"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

[neufer]

"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

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

http://asterisk.apod.com/viewtopic.php? ... ne#p156025

[Ann]

....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!

I use a software from Project Pluto, called Guide 8. It contains information, or assessments, for a lot of clusters. When I clicked on NGC 2425, a smallish window opened with the information I just described. The source used by Guide for this cluster, and for M46 and M47, is http://www.astro.iag.usp.br/~wilton/clusters.txt.

Ann

[LMartin]

It's going to Kuiper belt and back here in 6 yrs? Let's gravitationally attach a telescope next to it and get some nice picts of KBOs!

I think even comet's coma is less polluting the view than Earth's atmosphere. Although I'm not sure if there is any difference in delta v compared to sanding such scope as itself (taking comet's low mass into account).

[neufer]

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

No.

[NoelC]

At the time the animals came in the form of Methane

No cow pie in the sky:

http://www.jgpress.com/archives/_free/000550.html

-Noel

[Booster]

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?

[neufer]

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

<<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.>>

[Chris Peterson]

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 oceans amount to about a billion cubic kilometers of water. With a typical comet delivering perhaps one cubic kilometer of water, filling the oceans over a few tens of millions of years isn't unreasonable, given the expected number of comets diving into the inner Solar System at its early stages.

Collisions from comets might crater the Earth, but they wouldn't deliver enough energy (by many orders of magnitude) to significantly reheat the surface. And the energies involved would not dissociate most of the water; it would simply end up in the atmosphere as water vapor.

There is nothing about the history of the Solar System or basic physics that argues against much of the Earth's surface water coming from comets; it really just comes down to observational evidence of Kuiper Belt objects, and no doubt that will accumulate over the next years.

[TNT]

Hey, cool APOD! I've always wanted to see a comet, although I missed my chance with Comet Garradd...

Still, the picture with the comet and the two star clusters is amazing!

[zerro1]

This is a fantastic Image. Really nice star color. Well Done!

[Red Lord of Mars]

Hello..

First timer here... I wanted to ask if the small formation in the lower left corner of the pic is the Cat's Eye Nebula..

It looks so much like it, that I am surprised no one else noticed it...

Red Lord

[Chris Peterson]

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

It isn't the Cat's Eye Nebula, although it is another planetary nebula, NGC 2438. While it appears to be a member of M46, it is actually an unrelated object, probably between us and M46.

(The Cat's Eye is in Draco, which is very far from Puppis, where this APOD image lies.)