Cassini Finds Source of Icy Jets On Enceladus

Not long ago, we discussed Cassini's mission to "skeet-shoot" Saturn's moon Enceladus in order to take high-resolution pictures as close to the surface as possible. Well, NASA scientists found what they were looking for. A newly released mosaic shows 300-meter-deep fractures in Enceladus' surface which are the source of enormous icy plumes that periodically erupt into space, reaching hundreds of kilometers from the moon's surface. Another picture shows one of the fractures in closer detail.

Comments

Gross

[4D6963]

Ewww, Saturn has stretch marks all around its Enceladus!

Sorry, I know, I deserve my eventual -1 score.

Re:Gross

[4D6963]

Wow, mods, you shouldn't encourage me or anyone to make that kind of joke, really..

fastest computed camera turn?

[wisebabo]

So anyway this past flyby was at 30 miles at 50,000 mph. I understand that a future one will be done at 15(!) miles altitude (although I don't know the speed).

I've got to believe that that's the fastest low flyby that's ever been made. With Cassini going by at about 15 miles per second it'll be spinning quite rapidly (a revolution every couple of seconds?) to take one picture right? (there is no camera platform so the entire spacecraft must turn to aim).

Is there ANY other example of a camera that had to be turned so fast as to catch a moving (relative) target? With calculated precision of course, a photographer turning a camera to de-blur a passing race car doesn't count. There must be even faster motion compensation tricks for missile launches or maybe even roller-coaster rides right? What about industrial processes, anybody have any interesting examples? Then of course, are there any other ONE TIME events when they only had one chance to get it right?

Of course the other way to get a nice crisp shot would be to use a flash but even at "just" 15 miles it would take quite a flashbulb to illuminate the target sufficiently. Then again Cassini does have about 70kgs of plutonium on board...

Re:fastest computed camera turn?

[HertzaHaeon]

A faster camera movement? News photographers who capture certain spinning politicians perhaps?

Re:fastest computed camera turn?

[Anonymous Coward]

One revolution makes something 30 miles away appear to move 30*2*pi miles.

Rotation period = 30*2*pi miles / 15 miles per second = 12.5 sec.

Try to erase your mental image of something spinning rapidly.

Re:fastest computed camera turn?

[CheshireCatCO]

If you're thinking of the upcoming flyby in October, I don't expect that much imaging will occur. That flyby is optimized for the fields and particles instruments. The next imaging flyby is on Halloween and is at 200 km altitude.

Re:fastest computed camera turn?

[CheshireCatCO]

With a spacecraft the size of a bus, that's very fast. Especially considering that it takes tens of minutes to turn between targets, typically.

Just because you know things that can spin in less than 10 seconds doesn't mean that that's a reasonable rotation rate for every object.

Re:fastest computed camera turn?

[OriginalArlen]

As you say, the camera platform (actually, the entire s/c) can't slew that fast.Cassini was turned so that the ISS imager was pointing backwards at closest approach. Check out sims (further up that thread) that were done showing a big black square of sky that suddenly fills with Enceladus at extreme close-up. This was the only way they were able to get images of this quality.

False color?

[SoundGuyNoise]

Can someone please explain the technical reasons why so many space photos are "false color" based on X-Ray or infrared spectrum, even from modern spacecraft? Is there no color spectrum in outer space?

Re:False color?

[ColdWetDog]

Can someone please explain the technical reasons why so many space photos are "false color" based on X-Ray or infrared spectrum, even from modern spacecraft? Is there no color spectrum in outer space?

"False color" images, when not used to impress technically illiterate folks, are used to highlight information that would otherwise be difficult or impossible to discern. In TFA, researchers colored the smaller bits of 'snow' that would not be visible in the image at the viewed resolution. That helps discern a trend instantly that, I'm sure, took the researchers quite a bit more time to figure out.

Usually, they're just for looks. Like Paris Hilton.

Re:False color?

[colmore]

Different wavelengths reveal different things about what they're bouncing off of. I imagine it's done to get NASA the full range of data they're looking for. If your pressing scientific question isn't "what does this look like to a human if the human were there" then there's no particular reason to pick the visual spectrum over another range of wavelengths.

Re:False color?

[stuckinarut]

I assume by 'color spectrum' you are referring to visible light which our eyes are sensitive to and so allows us to see an image. The frequencies of electromagnetic radiation that are outside of this range can provide details that 'color' alone can't such as infra-red being able to penetrate dust that otherwise obscures the subject. Think of the impressive images of the Horsehead Nebula that were taken in infra-red as the Horsehead is believed to a dense cloud of tiny interstellar grains of dust that blocks the light of the emission nebula IC 434 and stars behind. While dark nebula are generally invisible (except of course where back lit as in the case of the Horsehead), their dust grains very effectively absorb light and ultraviolet radiation and then re-radiate this energy at infrared wavelengths.

Re:False color?

[uassholes]

The real colors would be boring to the scientists. Different wavelengths confer different information, and information is what they made the machines for.

For example here is a picture of a plume from Enceladus that was colorized for emphasis:
http://saturn.jpl.nasa.gov/multimedia/images/image-details.cfm?imageID=1874

But more specific examples for your question are these images:
http://www.nasa.gov/mission_pages/cassini/multimedia/pia06139.html
From the caption: "Red and green colors represent infrared wavelengths and show areas where atmospheric methane absorbs light."

http://chandra.harvard.edu/press/00_releases/press_030100a2142.html
In this case a picture in the X-ray spectrum allows them to see the temperature of the gas surrounding two colliding galaxy clusters; 50 to 100 million degrees C!

Re:False color?

[RJFerret]

Can someone please explain the technical reasons why so many space photos are "false color" based on X-Ray or infrared spectrum, even from modern spacecraft? Is there no color spectrum in outer space?

Of for a great visual comparison, see this flower in both visual spectrum (ho hum) and false color UV (bull's-eye!).

Even more impressive is all the details in this otherwise monochromatic flower that insects see.

The answer? To get information that our limited eyes can't perceive, into a range we can perceive, and therefore, learn from.

"In visible-light, a single photon can produce a single electron of charge in a pixel, and an image is built up by accumulating many such charges from many photons during the exposure time. When an X-ray photon hits a CCD, it produces enough charge (hundreds to thousands of electrons, proportional to its energy) that the individual X-rays have their energies measured on read-out." (per X-ray astronomy on Wikipedia) So it's also seems easier to capture these high energy wavelengths.

Sadly we can't make subtle IR observations from Earth, as the water vapor in our atmosphere absorbs a significant amount of that radiation. (per Infrared astronomy)

Re:False color?

[Anonymous Coward]

If your pressing scientific question isn't "what does this look like to a human if the human were there"...

It may not be a pressing scientific question, no, but it's definitely something that I'm certain many who follow these kinds of studies would love to know.

There is something very appealing about the idea of looking at a picture and knowing that if you were standing in that exact position, you would generally see the same thing. Whether it's in the form of HDR or false-color photos or any other technique, publishing a photo that isn't a visible-light-spectrum photo sacrifices that appeal of empathy for some artistic or scientific gain.

Yeah, I know, the visible light spectrum is boring. Sure, you might not be able to learn much from it, but with the number of devices they pile onto these rovers and landers, I would certainly see at least a little value in adding a standard little camera.

Re:False color?

[Goaway]

but with the number of devices they pile onto these rovers and landers

That number is very small.

And there's your entire answer for you, really. When we start hauling a space truck out there every week, you'll get your pictures. Until then, those are number #100 on a ten-point list.

Re:False color?

[turgid]

Usually, they're just for looks. Like Paris Hilton.

There's another Paris Hilton?

Re:False color?

[syousef]

Different features are seen in different light at different wavelengths.

For an everyday example: I am using an old video camera with infra-red "night-vision" mode as a baby monitor. My newborn can sleep in the dark and I can still tell if he's breathing from the other room without disturbing him. If I switch back to "normal" colour spectrum, I see nothing but a black screen. That's because my baby emits and reflects differently in infra-red than he does in visible light.

Well objects in space are much more extreme. They don't live in the same 50 degree celicius range that we humans almost always do. Temperatures range from just above absolute zero to millions of degrees. They don't live at almost exactly the same distance from our sun like we do. Within our own solar system, the further you go from the sun the less reflected light there is and the harder it is to capture images of large objects in visible light because there is less of it. (Ever tried to capture pictures at night or in a rock concert. If there's no fast motion you take long exposures, but if there is you're hosed. Well think about how fast space craft move).

So instead of give up altogether scientists turn to other wavelengths and see that some features show up better in different frequencies, and in space that works well. If you want to see what the sky looks like at different frequencies, take a look here. They have images of much of the sky at different wavelengths.

http://skyview.gsfc.nasa.gov/docs/easy.html
http://skyview.gsfc.nasa.gov/cgi-bin/query.pl

Unfortunately here on earth the atmosphere absorbs too much at most frequencies so a lot of observation is limited to use in orbital observatories and spacecraft.

Note: I have an Astronomy masters but have never worked in the field. I did the degree "for fun".

Re:False color?

[shawb]

That's because the space robots can not reveal the terrible secret of space. Now go stand by those stairs.

Re:False color?

[DMUTPeregrine]

There's another reason. You can assign a range to correlate to the visible spectrum. So instead of 400-700nm you set violet to red at some other point s in the more useful data. This gives a visualization of the image made in a spectrum we can't naturally see that has more detail than a greyscale image.

Re:False color?

[Smivs]

Another reason has to be the availability of light. Saturn's orbit is up to 1,513,325,783 km from the Sun (as opposed to Earth at up to 152,097,701 km), so far less light is available. basically a 'normal' photo would be so dark you couldn't actually see anything.

Hup hup huzza!

[colmore]

Way to go, Space Robot!

Jets? Plumes?

[owlnation]

No! It's spouts! Thar she blows!

Seems Earth's moon is not the only moon in our system with whales.

"Cassini Finds Source of Icy Jets On Enceladus"

[ZarathustraDK]

Frost-Xenu?

The Original Source

[CheshireCatCO]

With apologies for pimping the hard work of my co-workers over NASA's copies of the release, the website that originally carried this is http://ciclops.org/view_event/89/Targeting_the_Jet_Sources.

Re:Free water?

[CheshireCatCO]

The density of water (or anything else) in the plumes is awfully low and Enceladus is pretty deep in Saturn's gravity. You'd probably be better off mining water ice on a comet nucleus in the outer solar system or at least on a distant moon of one of the giant planets. (Which are basically captured comets.)

Moving jets?

[pudro]

Man, who could have predicted that these "jets" would be moving along these "cracks"? Oh, that's right, plasma cosmologists predicted that as soon as NASA found the "jets". They also predicted the shape of these "cracks" as well (which aren't shaped like cracks at all, but rather sharply cut v-trenches).

Too bad these plasma cosmologists spend all of this time thinking about how things work according to science instead of tweaking the mathematical equations of a scientifically-meaningless model (where over 90% of the universe is imagined by a hole-plugging theory) until they work out all of the flaws created by these pesky observations.

True, sometimes enchiladas cause jets

[uassholes]

But I love Mexican food.