Dawn Mission now Nearing Asteroid Ceres

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Michael Watson

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Message 1635424 - Posted: 31 Jan 2015, 0:59:59 UTC

The Dawn mission spacecraft is now nearing the asteroid Ceres. It has already taken some images that exceed the quality of those from the Hubble Space Telescope, which stood as the best available for many years.
A rather mysterious light-colored patch has been repeatedly photographed in the North polar region. Although Ceres is believed to have ice beneath its 10 to 20 mile-thick rocky crust, no firm evidence of ice on the surface has been found.
The next imaging session will be on Tuesday, Feb. 3rd, just four days from now. It will provide images of about 63 percent better resolution than its current best ones, which were released a few days ago. See article, linked below, for more details of the Dawn mission and two animated series of images of the dwarf planet rotating beneath Dawn's gaze.
http://dawnblog.jpl.nasa.gov/2015/01/29/dawn-journal-january-29/
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Message 1635432 - Posted: 31 Jan 2015, 1:21:49 UTC - in response to Message 1635424.  

Thanks Michael for the link.

I want to know what that white spot on Ceres is ?
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Michael Watson

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Message 1635469 - Posted: 31 Jan 2015, 2:44:12 UTC

Carbonate minerals, maybe, since it apparently isn't ice. These minerals are known to exist on asteroids. and some are light in color. I've measured the bright spot in the images. Given Ceres 590 mile diameter, it seems to be about 30 miles across. That's quite a big area for a deposit of a single type of mineral, especially on as small a world as Ceres. We'll have a better chance of understanding the real answer at each improvement in the clarity of the images, as Dawn continues toward Ceres.
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Message 1635580 - Posted: 31 Jan 2015, 7:26:14 UTC

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Message 1635605 - Posted: 31 Jan 2015, 9:33:21 UTC

Look forward to more info.
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Michael Watson

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Message 1637911 - Posted: 5 Feb 2015, 21:14:05 UTC

The new images of Ceres are out today. There are several sizable craters to be seen, notably in the South polar area. The bright spot that has attracted so much attention still appears quite large. The outline is now somewhat irregular, but a 35 mile diameter figure is probably not far off. There appears to be a much brighter, and much smaller spot within it. See linked article, below, for an animated series of the images, and further details.
http://astronomynow.com/2015/02/05/dawn-gets-closer-views-of-ceres/
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Message 1643390 - Posted: 17 Feb 2015, 21:59:29 UTC
Last modified: 17 Feb 2015, 22:01:33 UTC

NASA has just released two new images of Ceres, taken on Feb. 12th. A number of large craters can be seen, notably on the shadowed right side of each image.
The much-talked-about 'bright spot' can be seen near the top of the right hand image. It remains the most conspicuous feature on the planet.
Greater resolution has nearly eliminated pixelation artifacts from the images. The 'bright spot' still appears to be approximately rectangular. Its long axis is nearly vertical, in the image. It appears to be about 20 miles wide, by 30 miles, top to bottom.
See link, below, for new images:
http://www.jpl.nasa.gov/spaceimages/details.php?id=PIA19056
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Message 1643422 - Posted: 17 Feb 2015, 22:54:33 UTC - in response to Message 1643390.  

NASA has just released two new images of Ceres, taken on Feb. 12th. A number of large craters can be seen, notably on the shadowed right side of each image.
The much-talked-about 'bright spot' can be seen near the top of the right hand image. It remains the most conspicuous feature on the planet.
Greater resolution has nearly eliminated pixelation artifacts from the images. The 'bright spot' still appears to be approximately rectangular. Its long axis is nearly vertical, in the image. It appears to be about 20 miles wide, by 30 miles, top to bottom.
See link, below, for new images:
http://www.jpl.nasa.gov/spaceimages/details.php?id=PIA19056


Thanks Michael. So small and so mysterious.
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Message 1648584 - Posted: 2 Mar 2015, 21:35:58 UTC
Last modified: 2 Mar 2015, 21:41:52 UTC

A new series of animated images of Ceres has just been released. Although only about 44 % of the planet is illuminated, the images are spread out over time. We can observe all or most of Ceres surface, as it rotates before Dawn's camera.
The brightest of the bright spots is prominent in several of the images. It presents a squarish appearance, and is apparently not yet properly resolved.
The bright spot continues to be visible, even after Ceres rotation has carried the crater in which it lies onto the unlit portion of the planet. Neither floor nor even the rim of the crater can be seen, but the bright spot is still visible.
Interesting how the bright spot could reflect light from within a totally dark crater...
link to article, and images, below:
http://dawn.jpl.nasa.gov/feature_stories/NASA_Spacecraft_Nears_Historic_Dwarf_Planet_Arrival.asp
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Message 1648600 - Posted: 2 Mar 2015, 22:33:49 UTC - in response to Message 1648584.  

Thanks Michael, for the update.
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Message 1648620 - Posted: 2 Mar 2015, 23:42:17 UTC

I hope that by Friday they will have a better idea of what those bright spots are.
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Message 1648638 - Posted: 3 Mar 2015, 0:38:46 UTC - in response to Message 1648620.  

I hope that by Friday they will have a better idea of what those bright spots are.

They may believe they do, based on the new images. If this is something reflective, it's very likely that its above the elevation of the crater rim. This could suggest some kind of vapor plume.
The bright spot looks remarkably compact and bright for such a thing, though. When viewed at an angle it shows no height, where this might be expected of an expanding vapor plume.
There won't be any images better than those released today, until after April 10th, over a month away. Dawn is currently swinging away from Ceres, before it settles into a closer orbit.
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Message 1648738 - Posted: 3 Mar 2015, 7:46:00 UTC - in response to Message 1648638.  

I've watched the NASA conference on Dawn. Very interesting also on ion propulsion.
Tullio
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Message 1649147 - Posted: 4 Mar 2015, 15:40:33 UTC
Last modified: 4 Mar 2015, 15:45:33 UTC

I reviewed Monday's NASA press conference on Dawn at Ceres, with particular attention to the remarks about the bright spot. It was acknowledged that the bright spot appeared to remain bright, even when it had passed into shadow, as that point on Ceres rotated away from the Sun.
The apparent oddity of this was mentioned, with reservations about the current unavailability of detailed information about the slope angles of that particular site. It was further reported that the bright spot faded out as it reached the terminator. This last was a bit of a simplification of a more complex problem.

As anyone who has examined the terminator between light and dark portions of our own Moon with even a modest telescope will know, the boundary between light and dark is far from being a smooth line. It is rough and jagged and contains isolated areas of light within dark, and dark within light. These are caused by projections and depressions on the the surface of the Moon. These either catch light when all about it is dark, or are shadowed when the surroundings are illuminated.
Such is the case on Ceres, too. As the bright spot nears the terminator, the floor of the crater on which it lies falls into darkness. It will remain in darkness until the rotation of Ceres carries it around the planet, and it reaches sunrise. Despite the surrounding darkness, the bright spot remains bright.
It might be suggested that the bright spot is merely an elevated spot, perhaps a central peak of the crater.
This is apparently not the case. Another piece of information from the press conference was that such an elevation at the location of the bright spot had been carefully looked for, but none was found. This argues against a cryovolcano as the explanation of the bright spot. It also renders the bright spot a genuine mystery. It is one that must endure for at least five weeks, until new and better images of Ceres surface are secured.
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Message 1649469 - Posted: 5 Mar 2015, 7:26:43 UTC

How much talk a Silica based meteor can make? It's just a melted hardened glass or something similar...

Why?
Look where it's...in the middle of the crater...right in the middle...
So a meteor landed there...and in the process some kind of reflective thing (like mineral) has been made...maybe some glass from Silica based meteor? Or something like that...

Interesting...but not Aliens! :D

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Message 1649572 - Posted: 5 Mar 2015, 15:30:30 UTC

Naturally, I agree that it's premature to assume that extraterrestrial intelligence has anything to do with the bright spot on Ceres.
After seeing the latest series of images, it does not appear that a merely reflective patch on the floor of the crater, be that ice, or some mineral, will do, either.
The most reflective substance imaginable can not reflect light when there is none.
The floor of the crater in which the bright spot lies, falls into darkness as Ceres rotates. The bright spot remains visible, until it rotates out of sight. It can even be seen to be gradually foreshortened as this occurs, just as geometry leads us to expect, with a flat object.
The source of the bright spot's light appears to remain unexplained.
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Message 1649902 - Posted: 6 Mar 2015, 10:38:17 UTC

There is a mention of minerals, more often than water...though water is possible, you will not expect it in the middle of the impact crater on celestial body! ;)

Also, note that minerals do have different structures...some of which reflect light from different angles...so it also explains how the reflections came from the different angles in Ceres rotation...
;)

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Message 1649967 - Posted: 6 Mar 2015, 15:08:37 UTC
Last modified: 6 Mar 2015, 15:40:29 UTC

Dawn has entered in Ceres orbit today at 7.39 EST, says JPL, at a distance of 61000 km.
Tullio
Father Giuseppe Piazzi, SJ, who discovered Ceres on January 1 1801 would be glad.
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Message 1649972 - Posted: 6 Mar 2015, 15:28:21 UTC

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Message 1650717 - Posted: 8 Mar 2015, 17:16:26 UTC

When Hubble first photographed the bright spot on Ceres, in 2003 and 2004, it appeared to be about 1/7 of the diameter of the asteroid, or ~ 85 miles. It also appeared to be about 9 percent brighter than Ceres, as a whole, giving it an albedo of around 9.8 percent. The bright spot was not properly resolved, so the size and brightness figures were subject to correction, given better data.
Thanks to Dawn we now have such data. The current size of the bright spot currently appears to be about 8 miles, though it is still not resolved, and is presumably smaller. The apparent area of the bright spot has been reduced by ~113 times.
Absent any complicating factors, this should indicate that it is also about 113 times brighter than was inferred from the Hubble data. This works out to an albedo figure of ~ 1000 percent. Of course anything above 100 percent reflectivity is not a reflector, but a light source.
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Message boards : Science (non-SETI) : Dawn Mission now Nearing Asteroid Ceres


 
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