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Rosetta flyby of Asteroid Steins, 5th September 2008
elakdawalla
post Sep 12 2008, 01:10 AM
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Hi Phil, can you provide a link? I didn't see it on the homepage.


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volcanopele
post Sep 12 2008, 01:30 AM
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http://sci.esa.int/science-e/www/object/in...fobjectid=43380


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Rakhir
post Sep 12 2008, 12:49 PM
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And some details on the fly-by manoeuvres:
http://sci.esa.int/science-e/www/object/in...fobjectid=43369
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cndwrld
post Sep 12 2008, 01:09 PM
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The ESA SciTech newsletter that just came out includes the above plus another:

+ Details of the astonishing Rosetta fly-by of asteroid Steins can be read in "Rosetta Status Report No. 104 - Asteroid Steins Fly-by". This includes details of the asteroid fly-by manoeuvres which enabled the spacecraft to continuously keep asteroid Steins in the field of view of Rosetta's imaging instruments, while the spacecraft flew past the asteroid at a relative speed of 8.6 km per second.
http://sci.esa.int/jump.cfm?oid=43369

+ A colour composite image taken with the OSIRIS Narrow Angle Camera approximately 10.5 minutes before closest approach has been released.
http://sci.esa.int/jump.cfm?oid=43380

+ The first images of asteroid Steins, taken by the OSIRIS Wide Angle Camera during the fly-by of 5 September, were presented at a press conference the following day.
http://sci.esa.int/jump.cfm?oid=43361


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3488
post Sep 12 2008, 11:38 PM
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FWIW, I've enlarged & sharped a bit the view of 2867 Šteins, approx 10.5 minutes prior to CA & 9,500 KM using the NAC prior to safing.
Attached Image


Also here, brightness reduced & contrast enhanced. Shows the cavity quite well.
Attached Image


Andrew Brown.


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Harkeppler
post Sep 24 2008, 01:46 PM
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The jovian moon Thebe (here seen by Galileo) seems to show a nice similarity to asteroid 2867 Šteins: a large impact structure on an axis of symmetry and a conical end opposite to this crater.



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tasp
post Sep 24 2008, 06:26 PM
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Would that Thebe impact have consolidated materials not blasted out of the crater into a more resilient form that we now observe as the balance of the former larger Thebe that was chipped away by subsequent rocks ??

Mechanical shock effects might have 'welded' loosely compacted materials surrounding the crater into the form we now see. Maybe something similar happened to Steins, and perhaps many asteroids have this heritage.



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3488
post Sep 24 2008, 07:32 PM
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I suspect Thebe is a rubble pile held together by gravity. The 'pointy' end could be a 'shattercone' where at that end of the original larger object the impact that broke it occurred. With Thebe I have problems with that, i.e the giant crater suggests a rubble pile, not a shattered but hard body.

2867 Šteins, could be a shattercone, possibly once a part of the original larger Asteroid 434 Hungaria (which is now approx 20 KM in diameter).

Enormous deep craters are not that unusual.

Here is a montage I made of the Type C main belt Asteroid 253 Mathilde.
Attached Image


It is known that 253 Mathilde is of very low density, a 'rubble pile' held together, so the porous nature of the asteroid absorbs impacts like punching in polystyrene.

2867 Šteins, I'm not sire. I have not seen any gravity data from Rosetta. The volume of 2867 Šteins is known through the images, so using those together with pertubation data will yield the density. Or was Rosetta passing by too quickly to feel the tug from 2867 Šteins?

Perhaps if the NAC had worked, then greater detail of that 'large' crater on 2867 Šteins, may have helped determine if it's a hole in a rubble pile or was blasted out of more solid, but brittle material.

I assume 2867 Šteins is still thought of being composed of iron poor silicate rich basalt?

243 Ida also has a large crater, but the Galileo data suggested that 243 Ida was too dense to be a rubble pile, but perhaps some parts of the asteroid are not so coherent?

Also Mammoth Crater on main belt Asteroid 243 Ida. Some large boulders are visible.
Attached Image


Attached Image


Andrew Brown.


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"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before". Linda Morabito on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.
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cotopaxi
post Sep 24 2008, 10:21 PM
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Since this has come up a few times: Unfortunately Rosetta is not able to determine the mass (and therefore density) of Steins from the acceleration of the spacecraft by the asteroid. Flyby distance and velocity are too high, given the size of the asteroid.
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ngunn
post Sep 25 2008, 07:22 PM
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I notice that this colour image posted by Doug on the planetary society blog works rather well as a 3D anaglyph if you reverse the specs - right eye red:

http://planetary.org/image/steins_color.png

(Great stuff from the conference Doug - and I'm sure your presentation made a few converts.)
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djellison
post Sep 25 2008, 08:07 PM
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Emily was kind enough to be my copy-editor, picture-editor, arbitrator of facts - she dropped that image in smile.gif
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tedstryk
post Aug 10 2009, 02:58 PM
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I apologize in advance if this is a repost, but this is the most complete Steins WAC stet I have seen.


Attached Image


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elakdawalla
post Aug 10 2009, 04:21 PM
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That montage rang a bell -- with a little searching I realized that I made it! I composed it by grabbing the individual frames from the animation of the flyby that ESA posted here. Here's my post on it.

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tedstryk
post Aug 11 2009, 12:47 AM
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And here I thought ESA had made a new release smile.gif


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Paolo
post Dec 27 2009, 09:34 AM
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Reading the paper on Hubble observations of asteroid Lutetia (see parallel thread "Rosetta flyby of Asteroid Lutetia" I noticed that results from the Steins flyby are due for publication in 2010 (at last!) in "Science" and in a dedicated issue of "Planetary and Space Science"
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