by neufer » Fri Nov 05, 2010 2:10 pm
orin stepanek wrote:
Most of the venting is done on the smaller lobe; with some venting on the large lobe.
As one might expect since the most distant point from the mutual center of gravity
would, indeed, have the weakest gravity and the strongest centrifugal force.
However, it is the
side venting on the large lobe that probably keeps it spinning.
http://www.planetary.org/blog/article/00002759/ wrote:
The Planetary Society Blog
Hartley 2's jets By Emily Lakdawalla Nov. 4, 2010
<<It was a very happy set of scientists, engineers, managers, and administrators who filled the Jet Propulsion Laboratory's Von Karman auditorium this afternoon to do the postgame show on Deep Impact's flyby of Hartley 2. Project Manager Tim Larson remarked that the spacecraft and its navigators could not have performed better; the aimpoint for the flyby was missed by only two seconds in time and three kilometers in distance, which is pretty darned close to the mark. And of course, the images, as I mentioned previously, were spectacular.
I won't have time this afternoon to post a detailed writeup about the press briefing -- look for that tomorrow -- but I thought I'd post just one image from the briefing, the one that got a big "ooooh!" from the auditorium. It was part of co-investigator Jessica Sunshine's presentation on the appearance of the comet nucleus. It's an enhanced view of the part of the comet that is not directly lit by the Sun -- that is, the comet's night side, and the terminator (the day-night boundary). There are so many amazing things about this one photo. It's amazing how many jets there are. It is amazing that you can track the jets right down to where they are erupting from the sunlit surface. It is amazing that there are so many jets on the night side -- comets aren't supposed to do that. The nightside jets are not visible where they sprout from the surface; that's in the dark. You can see them where the dust from the jets has risen above the nightside shadow, into sunlight. You can even see where there are jets beyond the limb, on the back side of the comet, which, lit up by the Sun, show you where the comet's limb is. It's spectacular.>>
orin stepanek wrote:
Could this comet have a limited amount of icy material and will eventually become just another asteroid?
![Confused :?](./images/smilies/icon_confused.gif)
http://en.wikipedia.org/wiki/25143_Itokawa wrote:
<<Itokawa is an S-type asteroid. Radar imaging by Goldstone in 2001 observed an ellipsoid 630 ± 60 m long and 250 ± 30 m wide. The Hayabusa mission confirmed these findings and also suggested that Itokawa may be a contact binary formed by two or more smaller asteroids that have gravitated toward each other and stuck together. The Hayabusa images show a surprising lack of impact craters and a very rough surface studded with boulders, which were referred by the mission team as being in a 'rubble'. Furthermore, the density of the asteroid is too low for it to be made from solid rock. This would mean that Itokawa is not a monolith but rather a ‘rubble pile’ formed from fragments that have cohered over time.>>
[quote="orin stepanek"]
Most of the venting is done on the smaller lobe; with some venting on the large lobe.[/quote]
As one might expect since the most distant point from the mutual center of gravity
would, indeed, have the weakest gravity and the strongest centrifugal force.
However, it is the [b][color=#FF0000]side venting on the large lobe[/color][/b] that probably keeps it spinning.
[quote=" http://www.planetary.org/blog/article/00002759/"]
The Planetary Society Blog
Hartley 2's jets By Emily Lakdawalla Nov. 4, 2010
[float=right][img3="Hartley 2 is an unusually active small comet, a fact made clear by this enhanced view of its night side. Credit: NASA / JPL / UMD"]http://www.planetary.org/image/495737main_sunshine-4-4x3_full.jpg[/img3][/float]<<It was a very happy set of scientists, engineers, managers, and administrators who filled the Jet Propulsion Laboratory's Von Karman auditorium this afternoon to do the postgame show on Deep Impact's flyby of Hartley 2. Project Manager Tim Larson remarked that the spacecraft and its navigators could not have performed better; the aimpoint for the flyby was missed by only two seconds in time and three kilometers in distance, which is pretty darned close to the mark. And of course, the images, as I mentioned previously, were spectacular.
I won't have time this afternoon to post a detailed writeup about the press briefing -- look for that tomorrow -- but I thought I'd post just one image from the briefing, the one that got a big "ooooh!" from the auditorium. It was part of co-investigator Jessica Sunshine's presentation on the appearance of the comet nucleus. It's an enhanced view of the part of the comet that is not directly lit by the Sun -- that is, the comet's night side, and the terminator (the day-night boundary). There are so many amazing things about this one photo. It's amazing how many jets there are. It is amazing that you can track the jets right down to where they are erupting from the sunlit surface. It is amazing that there are so many jets on the night side -- comets aren't supposed to do that. The nightside jets are not visible where they sprout from the surface; that's in the dark. You can see them where the dust from the jets has risen above the nightside shadow, into sunlight. You can even see where there are jets beyond the limb, on the back side of the comet, which, lit up by the Sun, show you where the comet's limb is. It's spectacular.>>[/quote]
[quote="orin stepanek"]
Could this comet have a limited amount of icy material and will eventually become just another asteroid? :?[/quote]
[img3="[size=150][color=#0000FF][b]Another 25143 Itokawa[/b]?[/color][/size]"]http://s3.amazonaws.com/twitpic/photos/large/187903814.jpg?AWSAccessKeyId=0ZRYP5X5F6FSMBCCSE82&Expires=1288969443&Signature=tPHF0IDwHNj4fSBp194GE%2FqQmWc%3D[/img3][quote=" http://en.wikipedia.org/wiki/25143_Itokawa"]
[float=right][img3="Asteroid 25143 Itokawa observed by Hayabusa (Credit: JAXA)"]http://upload.wikimedia.org/wikipedia/en/b/b4/Itokawa4.jpg[/img3][/float]
[img3="Asteroid 25143 Itokawa orbit."]http://upload.wikimedia.org/wikipedia/commons/5/53/25143_Itokawa-orbit_Dec_3%2C_2006.gif[/img3]
<<Itokawa is an S-type asteroid. Radar imaging by Goldstone in 2001 observed an ellipsoid 630 ± 60 m long and 250 ± 30 m wide. The Hayabusa mission confirmed these findings and also suggested that Itokawa may be a contact binary formed by two or more smaller asteroids that have gravitated toward each other and stuck together. The Hayabusa images show a surprising lack of impact craters and a very rough surface studded with boulders, which were referred by the mission team as being in a 'rubble'. Furthermore, the density of the asteroid is too low for it to be made from solid rock. This would mean that Itokawa is not a monolith but rather a ‘rubble pile’ formed from fragments that have cohered over time.>>[/quote]