APOD: Saturn in Blue and Gold (2014 Apr 13)

[APOD Robot]

Saturn in Blue and Gold

Explanation: Why is Saturn partly blue? The above picture of Saturn approximates what a human would see if hovering close to the giant ringed world. The above picture was taken in 2006 March by the robot Cassini spacecraft now orbiting Saturn. Here Saturn's majestic rings appear directly only as a thin vertical line. The rings show their complex structure in the dark shadows they create on the image left. Saturn's fountain moon Enceladus, only about 500 kilometers across, is seen as the bump in the plane of the rings. The northern hemisphere of Saturn can appear partly blue for the same reason that Earth's skies can appear blue -- molecules in the cloudless portions of both planet's atmospheres are better at scattering blue light than red. When looking deep into Saturn's clouds, however, the natural gold hue of Saturn's clouds becomes dominant. It is not known why southern Saturn does not show the same blue hue -- one hypothesis holds that clouds are higher there. It is also not known why Saturn's clouds are colored gold.

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[Ann]

The fact that parts of Saturn can sometimes look blue is amazing to me, of course.

In the Observation Deck forum, Sandgirl recently posted an image of the hexagon of Saturn which looked amazingly, wonderfully blue. The page where the picture was originally shown is here.

Does anyone know if the blue color of the hexagon of Saturn as seen in that image has anything whatsoever to do with "reality"? In other words, what filter were used for that image and what color is the hexagon of Saturn? Will it, like parts of the northern hemisphere of Saturn, ever look blue due to Rayleigh scattering?

Ann

[niesamowity]

The blue color may be result from the diffraction of sunlight into the rings.

[Boomer12k]

From the article at Space.com---Saturn's Atmosphere: All the Way Down

"Saturn contains more sulfur than Jupiter, which give its zones and belts an orangish, smog-like cast."

There also is some oxygen, and water Ice, and other ice...and the reflection, refraction, may have something to do with it.

I also thought at first glance, the rings may diffuse some of the light also. But this does not always seem to be the case...I looked up COLOR pictures of Saturn, and while there are some that are blue, some are more golden...it could be filters and post production....If todays is Natural...then there has to be some natural mechanism for it.

It may also be SEASONS...and this would be due to the tilt of Saturn to the Sun....thus...some light is being filtered through the other layers, indirectly, thus not getting the same amount of exposure.

But I am just speculating....

:---[===] *

[hoohaw]

From the caption, "taken in 2006 March" YES, that is the way to write a date! So many people write dates in this format: 3/4/2014 and in Europe they write 4/3/2014 for the same date. Ambiguous and confusing. And this is improved over the previous standard, which was, e.g., 2/6/14. Well, folks, today is 2014 Apr 13 Sun. Sure it is longer, but it is utterly unambiguous, and it contains an error detector (congruence between 13 and Sunday). Above all I like the Sunday, omitted entirely from the other formats, yet day of the week is perhaps the most important feature of any date!

[Nitpicker]

Always a pleasure to see a Cassini image.

The sky appears blue on Earth when looking out into space in the daytime, not inward, no?

If a human were to look at Earth from an proportionate distance as Cassini to Saturn, the Earth's cloudless sky would be mainly transparent, except at the limbs of Earth. She'd see blue ocean, greeny/browny/whitish land and white clouds. Possibly a dumb question, but are the colours we see on Saturn due to scattering or reflection of sunlight?

[Chris Peterson]

The fact that parts of Saturn can sometimes look blue is amazing to me, of course.

In the Observation Deck forum, Sandgirl recently posted an image of the hexagon of Saturn which looked amazingly, wonderfully blue. The page where the picture was originally shown is here.

Does anyone know if the blue color of the hexagon of Saturn as seen in that image has anything whatsoever to do with "reality"? In other words, what filter were used for that image and what color is the hexagon of Saturn? Will it, like parts of the northern hemisphere of Saturn, ever look blue due to Rayleigh scattering?

I expect that the blue in that particular image is either completely artificial, or has been distorted by processing. Natural color images of the polar jet show just the same pale blue seen in today's APOD. Have a look at this page with the same raw data that is the source of the image you refer to. It has technical information, and you can go to the Cassini page and get the raw images (W00079604 - W00079611, eight images made through lots of filter combinations). Hard to know what was composited for the particular version you are looking at, though.

[Chris Peterson]

The sky appears blue on Earth when looking out into space in the daytime, not inward, no?

The sky scatters the same amount of blue upwards as it does down. It's just that when you're looking up, there's nothing behind the sky to interfere. You can see that the sky is blue in many images made looking down from space, because there's a faint blue cast present.

Possibly a dumb question, but are the colours we see on Saturn due to scattering or reflection of sunlight?

Both.

[Chris Peterson]

From the caption, "taken in 2006 March" YES, that is the way to write a date! So many people write dates in this format: 3/4/2014 and in Europe they write 4/3/2014 for the same date. Ambiguous and confusing. And this is improved over the previous standard, which was, e.g., 2/6/14. Well, folks, today is 2014 Apr 13 Sun. Sure it is longer, but it is utterly unambiguous, and it contains an error detector (congruence between 13 and Sunday). Above all I like the Sunday, omitted entirely from the other formats, yet day of the week is perhaps the most important feature of any date!

For computer files where the date is important, I always name them starting with yyyymmdd. That ensures that an alphabetical sort is also a date sort. For written numeric dates I never use slashes, either, as that is often ambiguous (as you note). I use the ISO standard, which is to use dashes: 2014-04-13. That can only mean yyyy-mm-dd. No two character dates, either.

But I don't think it matters in text if you write "March 2006" or "2006 March". Either is completely clear. The first is probably preferred because that's the way nearly everybody would say it. It flows better.

[Ron-Astro Pharmacist]

Has NASA ever considered attempting to insert some type of vehicle in amongst the debris of the rings to let it explore its contents?

[geckzilla]

For computer files where the date is important, I always name them starting with yyyymmdd. That ensures that an alphabetical sort is also a date sort. For written numeric dates I never use slashes, either, as that is often ambiguous (as you note). I use the ISO standard, which is to use dashes: 2014-04-13. That can only mean yyyy-mm-dd. No two character dates, either.

The Long Now Foundation uses yyyyy. They are prepared for the Y10k problem.

[Chris Peterson]

The Long Now Foundation uses yyyyy. They are prepared for the Y10k problem.

Seems rather short-sighted, if you ask me.

[geckzilla]

Yeah, I sort of expect The Longer Now Foundation to appear at some point.

[Ann]

The fact that parts of Saturn can sometimes look blue is amazing to me, of course.

In the Observation Deck forum, Sandgirl recently posted an image of the hexagon of Saturn which looked amazingly, wonderfully blue. The page where the picture was originally shown is here.

Does anyone know if the blue color of the hexagon of Saturn as seen in that image has anything whatsoever to do with "reality"? In other words, what filter were used for that image and what color is the hexagon of Saturn? Will it, like parts of the northern hemisphere of Saturn, ever look blue due to Rayleigh scattering?

I expect that the blue in that particular image is either completely artificial, or has been distorted by processing. Natural color images of the polar jet show just the same pale blue seen in today's APOD. Have a look at this page with the same raw data that is the source of the image you refer to. It has technical information, and you can go to the Cassini page and get the raw images (W00079604 - W00079611, eight images made through lots of filter combinations). Hard to know what was composited for the particular version you are looking at, though.

Thank you, Chris. On that page that you linked to, the color of the hexagon (and of the region close to it) looks a lot more "natural" or plausible. It is still bluer than I would have expected, but as you said, it may all have to do with what filter images were chosen for the finished picture.

Ann

[Anthony Barreiro]

The sky appears blue on Earth when looking out into space in the daytime, not inward, no?

The sky scatters the same amount of blue upwards as it does down. It's just that when you're looking up, there's nothing behind the sky to interfere. You can see that the sky is blue in many images made looking down from space, because there's a faint blue cast present.

If you look at the Moon in the daytime sky, the lighter colored highlands look white, while the darker maria look blue. I suppose this is a contrast effect, between blue-lighter-grey and blue-darker-grey, so that the lighter grey looks white and the darker grey looks blue.

[Chris Peterson]

If you look at the Moon in the daytime sky, the lighter colored highlands look white, while the darker maria look blue. I suppose this is a contrast effect, between blue-lighter-grey and blue-darker-grey, so that the lighter grey looks white and the darker grey looks blue.

Yeah. Although the lighter parts of the Moon that appear white would probably still appear bluish if you could compare them to an actual white reference. Our eyes are very poor at estimating color in any absolute sense.

[Nitpicker]

The Long Now Foundation uses yyyyy. They are prepared for the Y10k problem.

Seems rather short-sighted, if you ask me.

If humans are still using the same BCE/CE year reference in ~8000 years, we should:

a) give ourselves a pat for lasting so long,
b) slap ourselves for not coming up with a better year reference,
c) consider hexadecimal years, to keep four digits until year FFFF (65535 dec).

Year 9999 in decimal would become 270F in hex. Catchy and popular throughout the hexades!

[Nitpicker]

The Long Now Foundation uses yyyyy. They are prepared for the Y10k problem.

Seems rather short-sighted, if you ask me.

If humans are still using the same BCE/CE year reference in ~8000 years, we should:

a) give ourselves a pat for lasting so long,
b) slap ourselves for not coming up with a better year reference,
c) consider hexadecimal years, to keep four digits until year FFFF (65535 dec).

Year 9999 in decimal would become 270F in hex. Catchy and popular throughout the hexades!

Or maybe abandon hex as the stupid idea of a twit, and instead, to keep 4 digit years, define 9001CE equal to -999DE (or 999BDE), so that 10000CE is equal to 0DE. I call it "DE" for "D Era", as D comes after the C of the "Current/Common Era". I'll leave it to those entering the D Era to come up with a suitable word beginning with D, which is descriptive of their times: Droid, Dead, Dud, Dull, Divine?

Edit: yes, I want to introduce the radical concept of a year zero. You know it makes sense.

[geckzilla]

Edit: yes, I want to introduce the radical concept of a year zero. You know it makes sense.

The lack of year 0 is pretty annoying. It definitely makes sense, especially if you are a computer.

[BillBixby]

Edit: yes, I want to introduce the radical concept of a year zero. You know it makes sense.

The lack of year 0 is pretty annoying. It definitely makes sense, especially if you are a computer.

Feel free to insert a zero year as times transition into the aforementioned D era, if the prevailing 'Powers-That-Be' then recognize same. For European humans at the time of transition from BC to AD (BCE/CE?) the P.T.B. (that was?) was the Roman Empire, which had no zero in its Roman Numeral system. Therefore, no year zero back then.

With so many calendar adjustments thrown upon us, it is hard to figure out when some dates occurred. Thirty days hath September, April, June and November. All the rest have 31, except February which has 28 unless it in a year currently ending in a year evenly divisible by 4 in which case it will have 29 unless the year is evenly divisible by 100 in which case that year will have only 28 days in February unless the year is evenly divisible by 400 in which case it will have 29 days. So Feb 2000 was 29 days, Feb 1900 and 2100 should only have 28 days. February is Fouled Up Beyond All Recognition. Thankfully, we now seem to adjust time by leap seconds to keep our time constant with the universe, which is speeding away from us except for the parts which are speeding toward us.

Bill

[quigley]

Please forgive my utter lack of knowledge, but when considering gas giants such as Saturn, what happens to a probe vehicle that is sent into the clouds and beyond? Will it eventually heat up and disintegrate as in Earth's atmosphere? Do the gases become dense enough to slow down incoming objects? Could a durable and speedy enough vehicle make its way entirely through the entire diameter of Saturn's sphere? What were the "explosions" that were seen on the "surface" of Jupiter when it was struck by the comet fragments? Finally, are gas giants considered to be planets in the same way rocky worlds like our Earth are?

[Chris Peterson]

Please forgive my utter lack of knowledge, but when considering gas giants such as Saturn, what happens to a probe vehicle that is sent into the clouds and beyond? Will it eventually heat up and disintegrate as in Earth's atmosphere? Do the gases become dense enough to slow down incoming objects? Could a durable and speedy enough vehicle make its way entirely through the entire diameter of Saturn's sphere? What were the "explosions" that were seen on the "surface" of Jupiter when it was struck by the comet fragments? Finally, are gas giants considered to be planets in the same way rocky worlds like our Earth are?

They are all planets, by definition. Just different types. And yes, any body falling into a gas giant will burn up while still very high... that's what we saw with SL9. Even if you designed a probe able to withstand the heat of entry, it couldn't go through, since all the gas giants have solid centers.

[geckzilla]

Please forgive my utter lack of knowledge, but when considering gas giants such as Saturn, what happens to a probe vehicle that is sent into the clouds and beyond? Will it eventually heat up and disintegrate as in Earth's atmosphere? Do the gases become dense enough to slow down incoming objects? Could a durable and speedy enough vehicle make its way entirely through the entire diameter of Saturn's sphere? What were the "explosions" that were seen on the "surface" of Jupiter when it was struck by the comet fragments? Finally, are gas giants considered to be planets in the same way rocky worlds like our Earth are?

You wouldn't want a "vehicle" (who are you going to put in this death machine?) to go faster. It would survive much longer if it could go slower. If you could slow down the descent, pressure and wind would be the problems to worry about and I'm not sure which is harder to deal with.

Cassini is going to do this soon so we will have some actual data on what happens to a real probe when it takes the plunge. Like Chris said, it burns up high so imagine it as a little fireball high above the clouds. It's going to take the closest photos of Saturn's clouds possible, though. I'm very excited for these images.