Well done, Floyd!!!!!

Why not honor the discoverer by referring to this feature (and all future features of this type; that is, caused by the impact of undetected comets and asteroids) as Wesley’s Spot? As we honor the discoverers of comets, be they amateur or professional?

A more original name for this type of feature would be nice (admittedly "spot" is kind of uninspired). “Macula” is already in use for features on solid planetary and moon surfaces. This “spot” resembles and is in fact a kind of bruise or contusion – Latin for bruise is cicatrix, but Wesley’s Cicatrix doesn’t exactly roll off the tongue...

Problem is that it's extremely transient, Rogelio. It'll probably be completely gone in a few weeks, a few months at most.

I'm not sure- notice that the "cusp" of the bright south polar hood also looks doubled. I think this might be a seeing artifact or a hiccup in the AO system, if they were using AO.

John.

Hmm. I see what you mean, John. If this is the cause, then it's logical that the secondary image would be so pronounced since the primary's so bright.

In fact, at second glance it looked oddly 3D to me as well, almost as if the faint image was a reflection underneath the bright one, and THAT ain't real!

EDIT: Well...I dunno now, maybe it is a reflection @ Jupiter (not an AO artifact), but on an upper cloud layer. Presumably the bright IR source is deeper if both features are real.

EDIT2: JPL has updated their press release by adding Mr. Wesley's name. However, SpaceflightNow is running the earlier version as its lead story without his name. There ain't no justice.

Saw a mention of this on SpaceWeather this morning:

http://www.nasa.gov/topics/solarsystem/fea...p-20090720.html


-- Pertinax

I absolutely agree that Wesley's name should have been given from the outset, but note that "postdoctoral fellow" doesn't mean student. The person you're referring to definitely has a PhD and is playing a key role in the JPL observations (and it's his informative tweets that many of us are following!).

Edit: Sorry ugordan, I've now seen the original version of the JPL release, and can see that it's the release's authors who erroneously used the term "postdoctoral student" (corrected in the newer version that I first read).

This has been picked up on the NY Times breaking news blog (explicitly a blog, so not held to whatever standards [insert joke here] for official/published stories). From a viewpoint of someone familiar with NASA and astronomy, the comments are an interesting window to the public at large.

http://thelede.blogs.nytimes.com/2009/07/2...ark-on-jupiter/

Yeah, there's a scattering of crazies in there, but the comments don't seem too bad, on the whole. A word of caution- never read the comments on any youtube video, astronomy related or otherwise. Your brain will leak out of your ears!

Pass.

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.

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

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.

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.

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.

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




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.

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.)

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

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?

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.

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

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.

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).

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

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.

To be fair, given the bright background and having looked at the raw data, that Hubble image looks like a bad scan of an already poorly processed version. Looking at the moons in some of these early HST images and comparing them to modern webcams, the HST images have a slight edge, but that is all.

Yep, that's got "scan" written all over it, down to the print scratches on the high res version.

I'm sure that's true, but the fact that we're just two weeks from the 76th anniversary of film comedian Will Hay doing just that shouldn't go unremarked
<insert double take and grimace smiley>
http://cdsads.u-strasbg.fr//full/seri/MNRA...000085.000.html

http://archive.stsci.edu/proposal_search.p...st&id=12003

The HST observations have begun...the first set wrapped up about four hours ago.

Is that a restricted-access page, Ted? I get nothing but the frame.

Surprisingly good news, in any case!

It did that for me on the first few tries.

BTW, Gemini has also looked http://www.gemini.edu/node/11300

I'm assuming that with Hubble still in it's recommissioning phase and images not supposed to be released until some time in September we are unlikely to see these observations for some time??

EDIT: OK just saw this at spaceflight now http://www.spaceflightnow.com/news/n0907/24hubble/

"Engineers programmed Hubble to spend a few hours observing Jupiter Thursday afternoon. Imagery of Jupiter could be released by late Friday, according to Ray Villard, spokesperson for the Space Telescope Science Institute."

Definitely looking forward to this first example of the improved capabilities with WFP3.

Yes, and it's a shame they couldn't get the High Resolution Camera on ACS working again.

They repaired the ACS HRC, but it is much more complex to operate and would take much more time. At any rate, the WFC3, while having a much larger field of view than WFPC2, has significantly higher resolution than the PC chip in WFPC2, so this should be good.

They repaired ACS HRC? When? Last I heard the last servicing mission wasn't able to do that. Were they able to do it from the ground via some software method?

OK, I see that now, I didn't realize the HRC had further problems (although they are still trying to find a work-around).

Good SpaceflightNow article re yesterday's Hubble obs; images may be released later today!

Yup! http://hubblesite.org/newscenter/archive/releases/2009/23/

YESSSSS!!!

Wow. Obviously these are rush images that haven't been calibrated, but at first blush that hit looks a lot more pronounced than I remember for even the largest SL9 fragments. In fact, it almost looks like more dark material may have been boiling out from the deeper levels of the atmosphere since the impact occurred, and the 'ejecta field' to the left of center's still there.

Wow. Just wow. WFC3's performance is looking pretty good at this early stage as well!

Man, I love the Hubble! That picture is incredible

Sweet Fancy Moses!!!!!

Also, Surprise Collision on Jupiter Captured by Gemini Telescope

That downrange disturbance almost looks like the measurable effects of a shock-wave which in turn probably says something about the atmospheric density and structure in that region. Clearly there's a whole lot of derived science that likely will be gleaned from these images.

You know, if we keep seeing these things happen on Jupiter & (hopefully!) the other gas giants, we're going to have to come up with some sort of workable nomenclature for all these features.

Virtually every bit of impact terminology relates to solid matter (craters, ejecta, etc.). What do you call a persistent hole in a cloud deck that apparently spews stuff out & has other stuff laying around on surrounding clouds?

I sharpened the BW image slightly... this new camera is going to be amazing.

"Impact"... "dwarf impact"... "brush with"..."jeez, that was close!"...

Just don't put ME in charge of that...doubt that many (if any) of my terms would be printable!

Ordinary adjectives just aren't sufficient to describe these titanic events.

I think in the case of impacts onto gas giants, the old term for a meteor crater, "astrobleme," works well. It really is more of a blemish than a crater -- and like a blemish, it will fade over time.

Almost looks like there was the familiar-from-SL9 "black-eye" effect of downstream ejecta to the left, plus a very long, very dark ejected plume that pushed back out from left to right in these images. I get the feel of an impactor on a shallow, fast trajectory moving from right to left (in the Hubble images; all this would be reversed in the original discovery photos and the Gemini images), the "black-eye" ejecta pushing ahead of the impact site (perhaps defined by shock waves from the impact), and a plume of very dark material (mostly gas, I imagine) being fountained out of the impact site back along the impactor's track, from left to right, making up the very dark, now-deforming oval marking the astrobleme.

Just my gut-level feel from looking at these new, sharp images...

-the other Doug

Yeah, I was thinking about "astrobleme" myself, oDoug; it really is apropos for these things, as you pointed out.

I'm sure that there are hordes of scientists that would gladly give one or more internal organs to know exactly what that dark material is composed of. I suspect that it's some sort of precipitate: hot, formerly highly pressurized gas from down below that's abruptly been exposed to cold & low pressure in the cloudtops.

Wonder if astroblemes might be a productive molecular synthesis mechanism over time.