Jupiter Impact 2009 Options

[volcanopele]

Obviously, the quick comment that can be answered here (meaning not kooky), the impact scar is the ~ the size of Earth, NOT the impactor. Somehow there is some confusion about that among the commenters. The impactor was at best 1-2 km across, a faint object to observe from that distance. Not impossible by any means, we have observed outer moons of Jupiter that small, but we have no indication at this point that the impactor went through a period were it was temporarily captured by Jupiter, like SL9.

I think a lot of people in the general public extrapolate the fact that we have found nearly all the earth-orbit crossing asteroids of that size to mean that we have found all the objects in the Solar system of that size. That maybe another source of confusion.

[Mongo]

Will it be possible to determine the bulk nature of the impactor -- icy vs. rocky vs. iron? According to my understanding, a higher strength impactor would burrow further into Jupiter's atmosphere before fully disintegrating, thereby dredging up deeper (and presumably compositionally different) layers of that atmosphere, which might be detectable on large Earth-based telescopes.

The fact that the impactor was not detected prior to impact suggests (although it does not prove) that the impactor was relatively faint, suggesting a rocky or metallic composition to me.

Bill

[SFJCody]

Interestingly, there was a paper published in 1997 which said that the mean interval between impacts of comets >0.3km on Jupiter is on the order of 500 years. I guess the real figure might be a lot less than that.

[volcanopele]

Wasn't that based on two data points, Shoemaker-Levy 9 and the observation of a possible impact scar by Cassini (the astronomer, not the spacecraft)?

Obviously, it looks like the impact rate is greater than that, but I think with further study of this impact and comparisons with the impacts by the SL9 fragments, we can obtain an estimate of the impactors size assuming a similar composition and structure to the SL9 fragments.

[tedstryk]

Interestingly, there was a paper published in 1997 which said that the mean interval between impacts of comets >0.3km on Jupiter is on the order of 500 years. I guess the real figure might be a lot less than that.

Some put the size of she SL/9 parent body at 1-3 km. Given that many of the fragments made bigger marks than this, it is quite possible that this object is significantly smaller than .3 km.

[SFJCody]

Wasn't that based on two data points, Shoemaker-Levy 9 and the observation of a possible impact scar by Cassini (the astronomer, not the spacecraft)?

Yep, I believe so, and the paper detailing the possible 1690 impact is here.

Some put the size of she SL/9 parent body at 1-3 km. Given that many of the fragments made bigger marks than this, it is quite possible that this object is significantly smaller than .3 km.

The second page of this has a useful comparison of impact scar class to parent body diameter for SL9. The recent impact mark looks like it is well into the class 2 category, larger than any scar formed by sub 0.3km fragments of SL9. Still, I guess the impactor could have been smaller provided it also had a higher impact velocity or higher density than the SL9 fragments.

[Juramike]

Here's a paper putting the impact rate of 2 km comets at 4E-3 yr-1. (= one per 250 years average)

Zahnle et al. Icarus 163 (2003) 263-289. "Cratering rates in the outer Solar System." doi: 10.1016/S0019-1035(03)00048-4.

Full article freely available here (684 kb)


Either we've been really lucky and we've observed an extraordinary exciting period, or the impact rate needs to be adjusted upwards.
(Makes you wonder how many we've missed??? A permanent "Jupiter-cam" set of observatories might be a worthwhile investment.)

[dvandorn]

It occurs to me that the most massive objects in the Solar System ought to vacuum up the most pieces of debris per any given time period. And we know from the observations made for decades now by solar observatories that the Sun is probably the most frequently impacted body in the Solar System. (How many comets per year make death dives into our local star?)

It would make sense, then, that Jupiter would have the second-highest impact rate in the system. I know this is dependent on the relative abundance of potential impactors at various locations... but, on the scale of the entire system, it still makes sense to me.

-the other Doug

[djellison]

Two points - one is the "Friend or Foe" nature of of Jupiter- google that exact phrase for the research, it's very interesting.

Secondly - twice I've seen people cite Comet impact rates.

Who says this is a comet? Could have been an asteroid. If it's one 2km Comet / 250yrs, then what does the statistical distribution tell us for, say, 100m sized objects? 10x more frequent? 100x?

[Guest_Sunspot_*]

Hubble will be observing the spot in the next couple of days with it's new WFC3, along with Keck.

http://www.space.com/scienceastronomy/0907...ter-impact.html

It's pretty amazing to me that the image of the impact made by Anthony Wesley is as good if not better than the first image of Jupiter made by . Hubble in 1991

I guess it shows how bad the spherical aberration was.

[djellison]

Also shows how damn good the amateurs have got using the webcam techniques.

[4th rock from th...]

... A permanent "Jupiter-cam" set of observatories might be a worthwhile investment....

Amateurs already do that. You have almost 100% daily global coverage of Jupiter. Quality does vary, but on average it's very good. At least good enough to catch the present collision.
Also, please check the JUPOS project (http://jupos.privat.t-online.de/index.htm) for nice nice Jupiter feature position studies.
Of course, some funding might get more scientific results out of all that data.

[nprev]

Who says this is a comet? Could have been an asteroid.

True. I've been assuming that it was most likely an inbound long-period comet on a "bang for the buck" premise; think that would maximize impact kinetic energy while minimizing the object's mass (and therefore chances of pre-impact detection.)

There doesn't seem to be any way to really know for sure, though. The spectral signatures are undoubtedly dominated by indigenous Jovian material, so we'll never know the impactor's gross composition. Looks like the only potential clues would come from finding it in pre-impact imagery, and then only if there were enough of them to determine its orbit (assuming that it wasn't already captured like SL9).

[Juramike]

Amateurs already do that. You have almost 100% daily global coverage of Jupiter. Quality does vary, but on average it's very good. At least good enough to catch the present collision.
Also, please check the JUPOS project (http://jupos.privat.t-online.de/index.htm) for nice nice Jupiter feature position studies.
Of course, some funding might get more scientific results out of all that data.

Very cool! I didn't know about that!! (And I don't know if anyone in our local astronomy club is aware of it either (yet)).

Thanks muchly!!

-Mike

[4th rock from th...]

Regarding lesser known amateur planetary observation projects, ALPO has some long lasting programs.

I've participated with some Mercury images some years ago and at that time there were enough good images to monitor some permanent surface albedo features on the planet's unimaged side. Also, there's some work related to monitoring seasonal changes in Uranus. As for Venus, although there are frequent UV images, I'm not aware of any particular aspect being studied, just general cloud monitoring.