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#76 2014-01-24 18:56:01

SpaceNut
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Re: Dawn - Vesta & Ceres orbiter

http://www.nature.com/news/massive-aste … ff-1.14570

Previous studies spotted signs of hydrated minerals on the surface of Ceres1, and traces of neutral hydroxyl (OH, a breakdown product of water) in space around it, says Michael Küppers, a planetary scientist at the European Space Agency (ESA) in Villanueva de la Cañada, Spain. Hydroxyl strongly suggests the presence of water, he notes, but the measurements could not be confirmed during subsequent, more sensitive observations.

Data gathered in March 2013 suggest that the plumes originated from two widely separated, 60-kilometre-wide spots in the dwarf planet’s mid-latitude regions. Together, these spots ejected about 6 kilograms of water vapour into space each second.

http://www.skyandtelescope.com/news/Dwa … 39001.html

It’s great timing for the discovery as NASA’s Dawn probe is on its way to Ceres, likely arriving in orbit there in February 2015.

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#77 2014-12-31 19:43:14

SpaceNut
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Re: Dawn - Vesta & Ceres orbiter

Discovery awaits us as
Dawn begins final approach to dwarf planet Ceres. With the help of its electrically-powered ion propulsion system, Dawn will reach a circular orbit 8,400 miles from Ceres by late April.

hs-2005-27-d-print.jpg

Scientists believe Ceres formed like the rest of the solar system’s planets, but it failed to collect enough material to build up size. It measures nearly 600 miles across and has a spherical shape, according to imagery of Ceres taken by the Hubble Space Telescope.


Dawn’s ion thrusting was interrupted for four days in September when the probe was blasted by a high-energy particle of cosmic radiation, temporarily knocking the propulsion system offline.

As of Dec. 29, Dawn was about 400,000 miles from Ceres and closing in at around 450 mph, according to a JPL press release.

Under the new plan, Dawn will be snared by the gravitational tug of Ceres on March 6. But instead of Ceres pulling the probe directly into orbit 8,400 miles from the dwarf planet, Dawn will fly out in front of Ceres before its gravity — working together with continued thrusting from Dawn’s ion engines — gently captures the spacecraft.

The maneuver will be done without the need for a large conventional rocket burn performed on missions arriving at Mars or other planets.

Gravity capture means there will be fuel for later....

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#78 2014-12-31 20:25:00

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Re: Dawn - Vesta & Ceres orbiter

Yes! I've been waiting for this since Dawn launched.


"I guarantee you that at some point, everything's going to go south on you, and you're going to say, 'This is it, this is how I end.' Now you can either accept that, or you can get to work." - Mark Watney

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#79 2015-01-12 21:16:30

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Re: Dawn - Vesta & Ceres orbiter

Dawn of a strange new world

Dawn is slated to arrive at Ceres on Mar. 6. The spacecraft will enter the dwarf planet's orbit at an initial altitude of 13,500 km for a first full characterization. Then it will explore Ceres from survey orbit at 4,400 km, and next it will go lower to only 1,470 km.

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#80 2015-01-20 12:56:04

Void
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Re: Dawn - Vesta & Ceres orbiter

http://www.forbes.com/sites/bridainepar … net-ceres/

Dawns-first-close-image-of-Ceres.gif
I will let you guys play topper when it gets better.  For reference 80% as good as what Hubble showed.
I think the white spot is going to say a lot about what's going on.

I have had further thoughts.  It was almost certain that rocky and metal objects will have impacted Ceres, and the markings for that might be plainly visible.

If Ceres did have life, in an underground ocean, and if it later became frozen, I can still speculate on two methods it might persist.
1) If the Mantle is a world wide glacier, the I suppose convection would draw heat out of the world and output it to the universe, but since the gravity is so low, I would expect the cores porosity to be much more than that of the Earth.  So, perhaps fractures in the upper part of the core could still have liquid water in them.  Maybe brine.  Perhaps serpentinization was part of it's history.
2) If Iron/Nickel objects impact into the ice and generate a lake, then again repeated serpentinization even now.  If life could persist through the periods between such events, then it could exist now.

http://www.ncbi.nlm.nih.gov/pubmed/20572872

Last edited by Void (2015-01-20 13:48:39)


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#81 2015-01-28 08:14:46

Void
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Re: Dawn - Vesta & Ceres orbiter

Alright I have broken my promise to not play topper anymore about Ceres on this thread since you have not updated it.

http://www.latimes.com/science/sciencen … story.html

450x450

Time for me to speculate, and probably be wrong to a degree.  I just want to see how close I can get with limited information.  We can see what really is later, I hope.

I have been wondering how dirt could "Float on glaciers".

Pumice raft
http://en.wikipedia.org/wiki/Pumice_raft

We think that Ceres could not have volcanism now.  I might try to argue without much evidence that the solar wind might magnetically excite ferrite materials in the core and make enough heat for eruptive activity, but I am not going to push that much further.

If pumice were part of the dirt crust, and it were to dry out exposed to sunlight and vacuum, then the pores inside of it might constitute "Vacuum Balloons".
http://en.wikipedia.org/wiki/Vacuum_airship

However, since I don't want a beating I will back away from the word pumice, and substitute in for it the word porous soil particles which also might have "Vacuum Balloons" in their "VOIDS" smile

So if the world wide glacier below does exhibit tectonic subduction, perhaps the soil is too light to be sucked below.
http://en.wikipedia.org/wiki/Subduction

In the picture I have just seen, it looks like the "Crust" could be fairly thick, and if so, and if porous, may be like a winter coat, providing some thermal insulation.


http://www.solstation.com/stars/ceres.htm

Although classified as carbonaceous, Ceres reflects roughly 10 percent of the sunlight that strikes it ("albedo") and so is not as dark as other low-density asteroids called carbonaceous chondrites, which have albedos of around three to five percent. While exposed water ice would not be stable at the surface of Ceres at its relatively close distance to the Sun, water and ammonia do appear to be bound up in crustal minerals on the asteroid's surface. That Ceres has not lost these volatile components from destructive impacts suggests that the asteroid may be a surviving protoplanet from the formation of the Solar System. (More discussion is available from the Planetary Society.)

Water and ammonia do appear to be bound up in crustal minerals on the asteroid's surface.  So, maybe an Ammonia/Water/Salt ocean at the bottom of the ice where somehow this porous material can form, and be pulled up by upwelling warmer ice?

The white spot?  I am guessing a hole exposing clean ice?  Why would the ice be clean?  Cryo-Volcanism?  I guess maybe the ice would be clean?  Something else?

Last edited by Void (2015-01-28 08:18:10)


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#82 2015-01-31 21:15:37

Tom Kalbfus
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Re: Dawn - Vesta & Ceres orbiter

The white spot is probably a recent crater, usually recent craters are brighter than older ones.

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#83 2015-01-31 21:24:03

Void
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Re: Dawn - Vesta & Ceres orbiter

If forced to bet, I guess I would agree.  I still don't know why the ice is not dirty.  Maybe it just looks bright relative to the surroundings.  But we are likely to get a better view soon.


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#84 2015-02-01 08:41:32

Mark Friedenbach
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Re: Dawn - Vesta & Ceres orbiter

One can always hope it's a recent crater on an ice sheet (that's why it's clean).

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#85 2015-02-01 22:20:33

Tom Kalbfus
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Re: Dawn - Vesta & Ceres orbiter

Void wrote:

If forced to bet, I guess I would agree.  I still don't know why the ice is not dirty.  Maybe it just looks bright relative to the surroundings.  But we are likely to get a better view soon.

I believe the rest of Ceres is darkened by many micro-meteor impacts that pock the surface over time, the white area is a freshly dug new crater, so its surface hasn't been as exposed to space and as many micro-meteor hits as has the rest of Ceres, that is why I think it is white.

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#86 2015-02-01 22:39:58

Tom Kalbfus
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Re: Dawn - Vesta & Ceres orbiter

Mark Friedenbach wrote:

One can always hope it's a recent crater on an ice sheet (that's why it's clean).

It probably has more water than Mars, the main problem with Ceres is that it is small, it didn't get top billing as a planet, so policy makers haven't paid as much attention to it. Suppose we wanted to send astronauts to Ceres, would it be much harder than getting to Mars and landing on its surface? The thing about Ceres, is that once you get there you can make your own rocket fuel for the return trip, and you can do it much the same way as in Mars direct. Land a nuclear reactor on its surface, melt some water, and split it into hydrogen and oxygen, store liquid hydrogen in a permanently shadowed crater on Ceres. Let me check on Cere's axial tilt. Wikipedia says the axial tilt is 3 degrees, there ought to be some permanently shadowed craters in the polar regions of Ceres, this would make storing liquid hydrogen in tanks much easier. The escape velocity is a meager 0.51 km/sec, so you wouldn't need an ascent stage, what gets you off the surface would be the same thing that gets you back to Earth.

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#87 2015-02-02 06:44:17

Void
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Re: Dawn - Vesta & Ceres orbiter

Yes, that could be true Tom.  Actually, I turns out that the white spot may not be that white.  It might be darker than the photo implies.

http://en.wikipedia.org/wiki/Ceres_(dwarf_planet)

Surface[edit]

The surface composition of Ceres is broadly similar to that of C-type asteroids.[12] Some differences do exist. The ubiquitous features of the Cererian IR spectra are those of hydrated materials, which indicate the presence of significant amounts of water in the interior. Other possible surface constituents include iron-rich clay minerals (cronstedtite) and carbonate minerals (dolomite and siderite), which are common minerals in carbonaceous chondrite meteorites.[12] The spectral features of carbonates and clay minerals are usually absent in the spectra of other C-type asteroids.[12] Sometimes Ceres is classified as a G-type asteroid.[54]

The Cererian surface is relatively warm. The maximum temperature with the Sun overhead was estimated from measurements to be 235 K (about −38 °C, −36 °F) on May 5, 1991.[16]





Diagram showing a possible internal structure of Ceres
Only a few Cererian surface features have been unambiguously detected. High-resolution ultraviolet Hubble Space Telescope images taken in 1995 showed a dark spot on its surface, which was nicknamed "Piazzi" in honor of the discoverer of Ceres.[54] This was thought to be a crater. Later near-infrared images with a higher resolution taken over a whole rotation with the Keck telescope using adaptive optics showed several bright and dark features moving with Ceres's rotation.[7][55] Two dark features had circular shapes and are presumably craters; one of them was observed to have a bright central region, whereas another was identified as the "Piazzi" feature.[7][55] More recent visible-light Hubble Space Telescope images of a full rotation taken in 2003 and 2004 showed 11 recognizable surface features, the natures of which are currently unknown.[11][56] One of these features corresponds to the "Piazzi" feature observed earlier.[11]

These last observations also determined that the north pole of Ceres points

So, for what you propose, the surface never interacts with the mantles ice flows, which I would presume would involve the convention of warm ice up, and cold ice down.  I guess I was looking at the composition of the surface materials which imply contact with water, but maybe there is a different process that can produce these minerals in the cold vacuum in the presence of ice and water vapor and radiation?

Anyway one model I read did suggest that Ceres did melt initially, but the crust did not melt.  The crust being defined as the outer 10 K of material more or less.

So, the white spot is not hat white, so it could in fact be dirty glacier ice.  If that is true the impacts would spew dirty ice on the surface if they went deep enough.  Then evaporation would concentrate it into a less icy dirt.  But then that dirt has to have a method to stay on the surface.  Maybe if the surface does not circulate with the interior ice, the dirt stays there.  Otherwise?

I am sure my betters will say in time, if the probe continues on.


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#88 2015-02-05 20:42:01

Void
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Re: Dawn - Vesta & Ceres orbiter

http://tucson.com/news/blogs/scientific … de206.html

Its crust is believed to be icy, but don’t imagine a bright, frozen surface, said David O’Brien, one of the Dawn team members from PSI. Think mud, both frozen and liquid.

One telltale sign the scientists seek is whether Ceres has large craters at mid-latitudes. If it doesn’t, that means the planet has reshaped itself, possibly with the flow of that liquid mud at a glacial, geologic pace, O’Brien said.

Perhaps they mean fluid muddy ice, not liquid mud?  Maybe they mean liquid mud in the event of an impact.

http://abcnews.go.com/Technology/nasas- … d=28753587

ht_dwarf_planet_kab_150205_16x9_992.jpg

To me it looks like the lowest parts of the picture are much rougher than the rest.  Certainly craters made a major contribution to that, but I am not totally convinced that it was craters only.  The area above the rough area is bumpy, all the way to the top.  But perhaps other views would reveal that my eyes/mind are not getting sufficient information on this.  Alternately I wonder if it is a lopsided world.  One half rugged, one half smoother.  Mars is like that, Enceladus, is sort of like that where an ocean is on one side of the moon only.  Tiger stripes also.  It's odd that the bright spots are on the smother portion, but I suppose that could be random chance if they are impact marks.

The two obvious white dots?  The lower one looks like it splashed bright stuff.  Maybe a crater.  But, shouldn't ice be evaporating?  What I have read says the the places where they noticed water vapor were darker then average.  The article above suggests muddy ice.  The picture may not reveal the actual color of the "White" spots.  Perhaps they are darker.

How do craters "Scab" over?  I suppose if the hole then evaporated more of the ice, the walls dirt would cave in.  Otherwise, could their be electrostatic levitation which might move the dust around the surface?  Tom of course pointed out that dust will accumulate.  I wonder if small impactors could put the surface soil particles in sub-orbital paths that would tend to re-distribute it over time.

Hope you don't mind that I am poodle jumping over this topic Spacenut.  Fire away if you want.

Last edited by Void (2015-02-05 21:54:13)


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#89 2015-02-06 09:34:27

Void
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Re: Dawn - Vesta & Ceres orbiter

A crater that exposes expels brighter ice.
A condensation point for frost.
Something that expels salt.
?


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#90 2015-02-07 19:38:08

Tom Kalbfus
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Re: Dawn - Vesta & Ceres orbiter

One thing is for sure, there definitely are craters on Ceres. I guess it was hit by a few things while orbiting in the asteroid belt.

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#91 2015-02-08 00:08:32

Void
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Re: Dawn - Vesta & Ceres orbiter

I guess I will wait for the crew running it to tell what is what.  It does look like the craters have faded in a lot of places, but still it was or is a very slow process.

This could be an introduction to the outer solar system?  Sort of maybe.


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#92 2015-02-18 06:55:21

Void
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Re: Dawn - Vesta & Ceres orbiter

http://www.space.com/28579-ceres-bright … hotos.html

White spots.

ceres-photos-nasa-dawn.jpg?1424202922

My eyes think that the world has two different surfaces, a smoother one and a more rugged one.

The white spots seem to be mostly on the smoother side.

That's what I see anyway.  Better pictures required I suppose.

Last edited by Void (2015-02-18 09:15:11)


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#93 2015-03-07 23:27:08

SpaceNut
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Re: Dawn - Vesta & Ceres orbiter

NASA space probe 'Dawn' enters orbit of dwarf planet --

will stay over the mysterious body for 16 months to study its structure and gather clues to help mankind better understand how Earth and the other planets were created.

It took Dawn seven-and-a-half years and 3.1 billion miles to reach Ceres's orbit, after leaving Earth and stopping off at the Vesta asteroid for its previous exploration mission.

Dawn was captured by the dwarf planet's gravity at 1239 GMT, some 38,000 miles (61,000 kilometers) from Ceres's surface.

Gravity capture...nice

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#94 2015-07-28 20:02:57

SpaceNut
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Re: Dawn - Vesta & Ceres orbiter

As awe inspiring as Pluto has been the near by neighborhood is just as exciting....
Haze Detected Above Mystery Bright Spots on Ceres

The intriguing bright spots on dwarf planet/asteroid Ceres have been fascinating for the public and scientists alike. "At almost 621 miles (1,000 kilometers) in diameter, Ceres isn’t all that big by planetary standards, but is a good size for a dwarf planet or asteroid."

It also isn’t known yet what the spots themselves are composed of, but mission scientists have been leaning toward ice or salts as the two most likely explanations. Ice may sublimate into vapor, which could account for the haze. Also, if the spots are evaporated salts (or ice), they could be leftover deposits from active cryovolcanism, a form of volcanism involving water and ice instead of molten rock. Ceres’ mass is already known to be composed of at least one-quarter water, more than any other known asteroid, so it’s an intriguing possibility. Ceres may turn out to be more geologically active than anticipated.

Right now, Dawn is orbiting less than 2,485 miles (4,000 kilometers) above Ceres’ surface, and by August it will be less than 932 miles (1,500 kilometers). From that vantage point, it will have the best view yet of the spots and haze, the biggest surprises of the mission so far.

Some apparent shared characteristics with other bodies such as Pluto should help planetary scientists better understand the history of these fascinating worlds and how they evolved throughout the history of the Solar System.

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#95 2015-08-06 09:20:42

RGClark
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Re: Dawn - Vesta & Ceres orbiter

Just released today:

Tour Weird Ceres: Bright Spots and a Pyramid-Shaped Mountain.
http://www.youtube.com/watch?v=Inc9BtRip04

  Bob Clark


Nanotechnology now can produce the space elevator and private orbital launchers. It now also makes possible the long desired 'flying cars'. This crowdfunding campaign is to prove it:
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#96 2015-08-26 10:48:54

GW Johnson
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Re: Dawn - Vesta & Ceres orbiter

The pyramid-shaped mountain (or another one just like it) showed up in another photo release a day or two ago,  from a closer range observation.  It certainly looks like a crystalline material.  Can't be a permanent feature if it's ice,  because it would be subliming away into the vacuum.  The bright spots down in the craters appear to be exposed crystalline material,  too. 

Personally,  I'm not sure there's really any such thing as the traditional separate classes of asteroids and comets.  Looks to me like a smooth spectrum of bodies,  large or small,  with varying amounts of volatile ices mixed with rocky materials that include some sort of space-weathered organics.  Those seem to act as a cement to bond the loose rocky materials into a crust. 

There's something about having overlying regolith,  especially with the space-weathered organics bonding it into a crust,  that restricts the ice sublimation to very low rates,  in spite of essentially no gravity.  Warm 'em up and they outgas vapors.  Chill 'em down,  not so very much.  Those closer-in to the sun over the lifetime of the solar system seem to be drier on average. 

Not sure why Vesta seemed to be drier than Ceres,  but the rocky surfaces of both look exactly like the comets we've visited.  These things all seemed to have formed in the same way from the same sort of stuff,  but experienced different histories.  Which would lead to variable volatile content,  exactly what we see.

GW


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#97 2015-08-26 14:06:13

Void
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Re: Dawn - Vesta & Ceres orbiter

The story I have read about why Vesta and Ceres are different, is that Vesta formed before Ceres, when the radioactive elements had not decayed as much.

Such as:
http://starplan.dk/news/heterogenous-di … lar-system
Of course I am not an expert.

Anyway it is thought that Vesta would have heated up much more from radioactive decay than Ceres, and so the ices would have vaporized off of it.  But that is just a story.

I open myself up to egg on the face again, but I do think that salt could be involved in slowing down evaporation.  Some salt will be there no matter what.  How much it might help to slow down evaporation I cannot say.

If Ceres were like a comet, then for the spots, I might venture to speculate that actually there vents that entend to the subsurface.  What the bright spots are, condensate or residual salts, I cannot say.

Last edited by Void (2015-08-26 14:08:47)


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#98 2015-08-28 12:45:45

Void
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Re: Dawn - Vesta & Ceres orbiter

Also, I do agree with you that there is a mysterious method where volatile substances seem to hold where they should not.  I do not dispute what you have said, since I don't have any better information.

But I also ask about electrostatic charge.  If a (+) or (-) charge were left behind lets say a fraction of an inch or meter, it is not impossible that that would be attractive enough to try to retain evaporated molecules, forming a thin skin of vapor over a dirty, organic, salty, ice.

How this could occur, I do not have enough information, but if the solar forces selectively stripped away a (-) or (+) charge from evaporating gasses, then the remnant would potentially be of an opposing charge to the charge just under the surface of the "Ice".

I did not comment on the mountain, because I don't know how it formed.  A wild guess would be cryovolcanism, or perhaps it was a relatively more icy block that floated up in a "Sea" of heavier mud-ice.  Then it would have eroded into a cone, sort of.  But if that were the case, then it should have shed a bunch of dirt as the ice vaporized it into a cone, and that dirt should deposit at the base of it.


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#99 2015-08-29 10:13:27

GW Johnson
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Re: Dawn - Vesta & Ceres orbiter

I don't know enough about freezing salt water under zero-gee vacuum conditions.  Here on Earthly oceans,  freezing seawater usually forms sea ice of little or no salt content (it gets left behind in the unfrozen water).  How that plays out when all the water freezes,  I don't know.  I would hazard the guess that ices "out there" would be highly-variable in salt content.  How salt content might affect vapor pressure for sublimation,  I haven't a clue. 

All I know is that sublimation is rapid when the actual vapor pressure over the ice is less than the equilibrium value.  That actual vapor pressure=humidity in the atmosphere over the ice,  not the total pressure of the atmosphere over the ice.  That total atmosphere pressure being zero on an asteroid or a comet,  the vapor pressure is also zero.  Unless the ice is near absolute zero temperature,  it has to have a finite equilibrium vapor pressure.  So,  exposed,  it will sublime away,  given time.   

On Mars with gravity,  loose dry regolith offers a flow path for sublimed vapor through the porosity between the grains,  but with significant flow resistance.  Ice under regolith trying to sublime fills these pores with water vapor,  displacing the local "air".  The flow resistance makes the pressure at the source higher than the pressure at the exit (2 to 7 mbar on Mars).  If that source pressure is higher than the equilibrium vapor pressure for the buried ice at its temperature,  then sublimation mostly stops.  But there has to be a little,  for there to be a flow resistance pressure drop.  It's a dynamic equilibrium.

On asteroids and comets,  you have the space-weathered organics plugging up the regolith porosity,  and cementing it together with some tensile strength as a crust.  The vapor pressure in the porosity adjacent to the buried ice has to be equilibrium for ice at that temperature.  Rupture the crust,  and you outgas volatiles into vacuum.  I don't see why it would stop until that pocket of buried ice is gone,  although it might take significant time to occur. 

Move a comet closer to the sun and the ice warms,  raising the confined vapor pressure.  The crust ruptures,  letting the vapor stream out.  It carries regolith particle with it,  which is where comet tails come from.  Same sort of thing might have happened to some asteroids but not others,  depending upon each one's initial content of radionuclides as extra heating. 

Like I said,  I really don't see much difference between asteroids and comets.  The only real variables appear to be mass and volatile content.  Don't yet see much way to determine volatile content without landing and drilling wells.  Very much like prospecting for oil and gas,  actually. 

We're going to need space ships with drill rigs on them,  it appears.  And a means to hold on while drilling.  What Philae had for holding on didn't work.  We've much to learn before we can make asteroid mining into a real business. 

GW

Last edited by GW Johnson (2015-08-29 10:18:04)


GW Johnson
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#100 2015-08-29 16:30:14

RGClark
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Re: Dawn - Vesta & Ceres orbiter

Just released image of the mysterious Ceres mountain imaged at closer Survey mission distance:

Aug. 25, 2015
Dawn Sends Sharper Scenes from Ceres.
pia19631.jpg
http://www.nasa.gov/jpl/dawn-sends-shar … from-ceres

  Bob Clark


Nanotechnology now can produce the space elevator and private orbital launchers. It now also makes possible the long desired 'flying cars'. This crowdfunding campaign is to prove it:
Nanotech: from air to space.
https://www.indiegogo.com/projects/nano … 13319568#/

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