Jupiter's New Impact Scar (2009 July 23)

[emc]

http://apod.nasa.gov/apod/ap090723.html

If these Jovial impact scars aren’t craters… are they dip in dots?

[bystander]

If these Jovial impact scars aren’t craters… are they dip in dots?

How do you crater clouds?

[orin stepanek]

If these Jovial impact scars aren’t craters… are they dip in dots?

How do you crater clouds?

At the risk of second guessing; I think Ed wants to know just what the scar is.
Orin

[neufer]

If these Jovial impact scars aren’t craters… are they dip in dots?

How do you crater clouds?

At the risk of second guessing; I think Ed wants to know just what the scar is.

Take your choice:

1) The evaporation of overlying white ammonia crystal clouds
2) The vertical mixing of different colored Jovian atmospheric components
3) The insertion of dirty ice cometary or asteroid components
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<<Jupiter is perpetually covered with clouds composed of ammonia crystals and possibly ammonium hydrosulfide. The clouds are located in the tropopause and are arranged into bands of different latitudes, known as tropical regions. These are sub-divided into lighter-hued zones and darker belts.

The cloud layer is only about 50 km deep, and consists of at least two decks of clouds: a thick lower deck and a thin clearer region. There may also be a thin layer of water clouds underlying the ammonia layer, as evidenced by flashes of lightning detected in the atmosphere of Jupiter. (Water is a polar molecule that can carry a charge, so it is capable of creating the charge separation needed to produce lightning.) The water clouds can form thunderstorms driven by the heat rising from the interior.

The orange and brown coloration in the clouds of Jupiter are caused by upwelling compounds that change color when they are exposed to ultraviolet light from the Sun. The exact makeup remains uncertain, but the substances are believed to be phosphorus, sulfur or possibly hydrocarbons. These colorful compounds, known as chromophores, mix with the warmer, lower deck of clouds. The zones are formed when rising convection cells form crystallizing ammonia that masks out these lower clouds from view

The carbon dioxide, carbon monoxide and water present in the upper part of the atmosphere is thought to originate from comets crashing into the planet, such as comet Shoemaker-Levy 9. The water cannot come from the troposphere because the cold tropopause acts like a cold trap, effectively preventing water from rising to the stratosphere.>>

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[NoelC]

An impact like that can churn up heavy stuff from wayyy down deep. Apparently Jupiter has a black heart.

What really scares me is no one saw it coming. Granted we don't actively watch the skies for potential impactors on other planets, but if that had hit us instead we'd all be black stuff in the clouds.

-Noel

[neufer]

An impact like that can churn up heavy stuff from wayyy down deep. Apparently Jupiter has a black heart.

It might have simply dispersed/evaporated the overlying white ammonia clouds
in which case, perhaps, it was nothing more than a very large Tunguska Event:

<<The Tunguska Event, or Tunguska explosion, was a powerful explosion that occurred near the Tunguska River in what is now Krasnoyarsk Krai of Russia, at around 7:14 a.m. on June 30, 1908. Although the cause of the explosion is the subject of debate, it is commonly believed to have been caused by the air burst of a large meteoroid or comet fragment at an altitude of 5–10 kilometres (3–6 miles) above the Earth's surface. Different studies have yielded varying estimates of the object's size, with general agreement that it was a few tens of metres across.>>

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What really scares me is no one saw it coming. Granted we don't actively watch the skies for potential impactors on other planets, but if that had hit us instead we'd all be black stuff in the clouds.

Well...not all of us.

It is possibly just near the threshold size needed for doing global damage:

<<Studies have shown that the risk from cosmic impact increases with the size of the projectile. The greatest risk is associated with objects large enough to perturb the Earth's climate on a global scale by injecting large quantities of dust into the stratosphere. Such an event could depress temperatures around the globe, leading to massive loss of food crops and possible breakdown of society. Various studies have suggested that the minimum mass impacting body to produce such global consequences is several tens of billions of tons, resulting in a groundburst explosion with energy in the vicinity of a million megatons of TNT. The corresponding threshold diameter for an asteroid is between 1 and 2 km. Smaller objects (down to tens of meters diameter) can cause severe local damage but pose no global threat.>>

[The Code]

Well...not all of us.

It is possibly just near the threshold size needed for doing global damage:

When you say the word possibly Does this mean you have Not got a clue?

The impact scares the hell outer me... Check This

http://edition.cnn.com/2009/TECH/space/ ... teor.scar/

There is as much space between the eye of a needle as there is in the hole universe...

Swainy

[emc]

If these Jovial impact scars aren’t craters… are they dip in dots?

How do you crater clouds?

Just a dumb joke - trying to be jovial... and playing with words.


Closest to cratered clouds I could find... http://gastateparks.org/info/cloudland/

[The Code]

emc

Feel the breeze at 100mph on a motor bike?

Now speed your bike up to 65,000mph and feel that breeze... (Just an example ..)

Mark

[Chris Peterson]

Now speed your bike up to 65,000mph and feel that breeze...

The minimum impact speed on Jupiter is about 60 km/s, or 135,000 mph. Statistically, the object was likely to have been moving a good deal faster than that. (The maximum would be around 200,000 mph for a collision with another body orbiting the Sun; it could be higher for a comet with a hyperbolic orbit.)

[neufer]

Now speed your bike up to 65,000mph and feel that breeze...

The minimum impact speed on Jupiter is about 60 km/s, or 135,000 mph. Statistically, the object was likely to have been moving a good deal faster than that. (The maximum would be around 200,000 mph for a collision with another body orbiting the Sun; it could be higher for a comet with a hyperbolic orbit.)

Escape velocity adds as an energy term. (A mistake I, myself, have made. )

Code: Select all

12.57 km/s : equatorial rotational velocity
13.07 km/s : circular orbital velocity 	
18.48 km/s : hyperbolic orbital velocity  = 13.07 km/s * SQRT[2]

59.5 km/s : escape velocity 	

59.5 km/s = Minimal impact speed = SQRT[59.5^2]
74.1 km/s = Maximal impact speed = SQRT[59.5^2 + (12.57 + 13.07 + 18.48)^2]

165,560 mph = Maximal impact speed

[Chris Peterson]

Escape velocity adds as an energy term.

That's true, you need to treat it as the sums of squares. In practice it doesn't make a big difference, however. Also, the problem should properly be treated using vector math, not just summing up speeds. Again, it doesn't make a big difference for estimating the approximate impact speeds.

12.57 km/s : equatorial rotational velocity
13.07 km/s : circular orbital velocity
18.48 km/s : hyperbolic orbital velocity = 13.07 km/s * SQRT[2]
59.5 km/s : escape velocity

In this case, the collision was near the south pole, so the rotational velocity doesn't have much effect. If the body was in a hyperbolic orbit, it could be very much faster than 13 km/s- there is no upper limit here (of course, there are limits to what is likely). The minimum collision speed could actually be lower as well, if the colliding body was in orbit around Jupiter (which isn't likely, but is possible).

So I'd put the maximal impact speed, given a body in a low eccentricity, retrograde solar orbit at more like 150,000 mph.

Still, you don't want to poke your head out the window when you're moving that fast!

[neufer]

12.57 km/s : equatorial rotational velocity
13.07 km/s : circular orbital velocity
18.48 km/s : hyperbolic orbital velocity = 13.07 km/s * SQRT[2]
59.5 km/s : escape velocity

In this case, the collision was near the south pole, so the rotational velocity doesn't have much effect. If the body was in a hyperbolic orbit, it could be very much faster than 13 km/s- there is no upper limit here (of course, there are limits to what is likely). The minimum collision speed could actually be lower as well, if the colliding body was in orbit around Jupiter (which isn't likely, but is possible).

Any comet nudged out of the Oort cloud will have
EXACTLY twice the kinetic energy per kilogram
of any circularly orbiting planet that it might encounter.

In any event, for Jupiter the dominant energy component is ALWAYS the 60 km/s escape velocity itself.

This is close to the average earth/comet collisional impact of about 53 km/s escape velocity.

For Mercury the dominant energy components are ALWAYS the cometary & orbital velocities
which combined average out to about 83 km/s but could be as great as 136 km/s.

So I'd put the maximal impact speed, given a body in a low eccentricity, retrograde solar orbit at more like 150,000 mph.

Still, you don't want to poke your head out the window when you're moving that fast!

You don't want to have a window open when you're moving that fast!

[Bill Melater]

Every photo of the impact that I have seen before tonight showed the impact site at the bottom of the photo.

Did the newspapers flip it to compensate for Oz astronomers standing upside down?

[Chris Peterson]

Every photo of the impact that I have seen before tonight showed the impact site at the bottom of the photo.
Did the newspapers flip it to compensate for Oz astronomers standing upside down?

Unless you go out of your way to orient astroimages in a particular way, the directions are usually arbitrary. The first image was released with the impact at top. Since then, I've seen different orientations.

[fugfar]

wow, thats earth sized huh? i knew jupiter was big, but that gives you a good perspective on it.
what im wondering, kind of already been answered, but if anyone can elaborate, why do these impact scars appear black, and how long will they be visible?
also, does anyone have a good estimate of the actual size of the thing that took the plunge?
i know impacts happen on all celestial bodies, would i be correct in thinking impacts are a lot more common or likely with jupiter because of its huge gravitational pull?

any answers or thoughts would be welcome, seems like there are some great posters here.
and how do i thank that guy in Australia? lol
-fugfar

[neufer]

wow, thats earth sized huh? i knew jupiter was big, but that gives you a good perspective on it.
what im wondering, kind of already been answered, but if anyone can elaborate, why do these impact scars appear black, and how long will they be visible?

It is currently assumed to be a small comet the size of Shoemaker-Levy 9 cometary fragments: 1 to 2 km in diameter. The visible scars from the Shoemaker-Levy 9 impacts were observed on Jupiter for many months after impact.

However, IMHO it could have been due to a comet as small as P/2007 R5 (i.e., only 100-200 meters in diameter) with a Tunguska type air burst dissipating/evaporating the overlying white ammonia Jovian clouds. If this is so the visible scar probably won't last "for many months."

i know impacts happen on all celestial bodies, would i be correct in thinking impacts are a lot more common or likely with jupiter because of its huge gravitational pull?

Even ignoring Jupiter's huge gravitational pull this large planet plows through a torus shell path 650 times larger in volume than the torus shell path of earth so it should probably intercept at least 650 times as many comets. Adding on Jupiter's gravity that factor is probably in the thousands.

<<Comet Shoemaker-Levy 9 (SL9, formally designated D/1993 F2) was a comet that broke apart and collided with Jupiter in July of 1994. SL9 was later observed as a series of fragments ranging up to 2 km (1.2 mi) in diameter. These fragments collided with Jupiter's southern hemisphere between July 16 and July 22, 1994, at a speed of approximately 60 km/s (37 mi/s). The prominent scars from the impacts were more easily visible than the Great Red Spot and persisted for many months.

The visible scars from the impacts could be seen on Jupiter for many months. They were extremely prominent, and observers described them as more easily visible even than the Great Red Spot. A search of historical observations revealed that the spots were probably the most prominent transient features ever seen on the planet, and that while the Great Red Spot is notable for its striking colour, no spots of the size and darkness of those caused by the SL9 impacts have ever been recorded before.[25]

Spectroscopic observers found that ammonia and carbon sulfide persisted in the atmosphere for at least fourteen months after the collisions, with a considerable amount of ammonia being present in the stratosphere as opposed to its normal location in the troposphere.

Counterintuitively, the atmospheric temperature dropped to normal levels much more quickly at the larger impact sites than at the smaller sites: at the larger impact sites, temperatures were elevated over a region 15,000 to 20,000 km (9,300 to 12,000 mi) wide, but dropped back to normal levels within a week of the impact. At smaller sites, temperatures 10 K higher than the surroundings persisted for almost two weeks. Global stratospheric temperatures rose immediately after the impacts, then fell to below pre-impact temperatures 2–3 weeks afterwards, before rising slowly to normal temperatures.>>

[DavidLeodis]

It would seem likley to be a time but could someone please let me know what 15:55.6 Z means on the image. Thanks.

[Chris Peterson]

It would seem likley to be a time but could someone please let me know what 15:55.6 Z means on the image. Thanks.

Z means "Zulu", a slightly dated synonym for UTC (coordinated universal time) that is still popular in the aviation and weather communities. Most astronomers would probably give this time as UT 15:55.6.

[DavidLeodis]

Wow that was a quick reply. Thanks for that information Chris.

[Chris Peterson]

what im wondering, kind of already been answered, but if anyone can elaborate, why do these impact scars appear black, and how long will they be visible?

Our knowledge of these things is limited to one previous observation (SL9), so there's a lot more to learn. Based on that impact, we might expect the scar to remain visible from a few weeks to a couple of months. The coloration is related to the particular deeper atmospheric gases exposed by the collision.

also, does anyone have a good estimate of the actual size of the thing that took the plunge?

The scar is the result of the energy deposited in the atmosphere by the collision, and that energy is proportional to the mass, and to the velocity squared. So a small mass at high speed would have a similar effect to a high mass at lower speed. SL9 was in that second category. Nobody knows in this case, but if you look at the SL9 scars, and plug in some sort of reasonable speed for this new impactor, you end up with something with a size around 1km. It's still just an educated guess, however.

i know impacts happen on all celestial bodies, would i be correct in thinking impacts are a lot more common or likely with jupiter because of its huge gravitational pull?

That's an interesting question, one I've thought about a lot in the past. I don't know a good way to answer it without some sort of simulation. My thinking is that Jupiter's gravity isn't a factor, however. Objects with strong gravitational fields certainly affect the orbits of objects passing by, but they don't necessarily increase the chance of a collision. Jupiter is a large planet, of course (as you noted), so it has a much larger collisional cross-section than other planets. That means it will collide with more debris than the other planets, regardless of its gravitational field.

[neufer]

i know impacts happen on all celestial bodies, would i be correct in thinking impacts are a lot more common or likely with jupiter because of its huge gravitational pull?

That's an interesting question, one I've thought about a lot in the past. I don't know a good way to answer it without some sort of simulation. My thinking is that Jupiter's gravity isn't a factor, however. Objects with strong gravitational fields certainly affect the orbits of objects passing by, but they don't necessarily increase the chance of a collision. Jupiter is a large planet, of course (as you noted), so it has a much larger collisional cross-section than other planets. That means it will collide with more debris than the other planets, regardless of its gravitational field.

About half of the first time hyperbolic cometary orbits that pass near to Jupiter will be inserted into a periodic elliptical cometary orbit that will automatically return to vicinity of Jupiter's orbit many times. This would make a future impact with Jupiter likely (as was the case of SL 9).

[neufer]

It would seem likley to be a time but could someone please let me know what 15:55.6 Z means on the image. Thanks.

Z means "Zulu", a slightly dated synonym for UTC (coordinated universal time) that is still popular in the aviation and weather communities.

Most astronomers would probably give this time as UT 15:55.6.

Sounds like a good time for a product placement:

[Chris Peterson]

About half of the first time hyperbolic cometary orbits that pass near to Jupiter will be inserted into a periodic elliptical cometary orbit that will automatically return to vicinity of Jupiter's orbit many times.

That's the value I'm uncertain of. How did you determine it?

[neufer]

About half of the first time hyperbolic cometary orbits that pass near to Jupiter will be inserted into a periodic elliptical cometary orbit that will automatically return to vicinity of Jupiter's orbit many times.

That's the value I'm uncertain of. How did you determine it?

I'm not giving you the real value you are searching for...just a hand waving first stab at the logic:

A near Jupiter pass has a 50-50 chance of losing or gaining energy.
Those that gain energy will be ejected from the solar system.
Those that lose energy will go into an elliptical orbit that will return to "the scene of the crime."

Eventually the comet & Jupiter will return to "the scene of the crime" at the same time
and (barring a collision) the comet will again have a 50-50 chance of losing or gaining energy.

However, since the comet is now already in an elliptical orbit it has a better than 50-50 chance of remaining in an elliptical orbit.

Eventually, after n encounters some (reasonable?) fraction of the comets that initially passed within m radii of Jupiter will end up crashing on Jupiter (just like SL9).