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?

[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.

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)

"Cassini Finds Source of Icy Jets On Enceladus"

[ZarathustraDK]

Frost-Xenu?