APOD: Sputnik Planum vs. Krun Macula (2016 Jun 18)

Comments and questions about the APOD on the main view screen.
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APOD: Sputnik Planum vs. Krun Macula (2016 Jun 18)

Post by APOD Robot » Sat Jun 18, 2016 4:05 am

Image Sputnik Planum vs. Krun Macula

Explanation: Pluto's pitted plains meet rugged highlands in this stunning view. On the left lies a southeastern extent of the bright region still informally known as Sputnik Planum. At right the edge of a dark region, informally Krun Macula, rises some 2.5 kilometers above the icy plains. Along the boundary, connected clusters of large pits form deep valleys, some over 40 kilometers long with shadowy floors. Nitrogen ice is likely responsible for the more reflective plains. The dark red color of the highlands is thought to be from complex compounds called tholins, a product of ultraviolet light induced chemical reactions with methane in Pluto's atmosphere. The enhanced color image includes portions of the highest and second highest resolution image data from the New Horizons July 2015 flyby of the distant world.

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Re: APOD: Sputnik Planum vs. Krun Macula (2016 Jun 18)

Post by Boomer12k » Sat Jun 18, 2016 6:48 am

Interesting... like looking at The Moon's Terminator.... deep shadows on right.

I wonder if over time those deep crater areas were gouged out by Geysers... like Enceladus, but nitrogen gas, or Methane escaping from underground....some look a bit like cinder cone volcanoes.

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Re: APOD: Sputnik Planum vs. Krun Macula (2016 Jun 18)

Post by delgado@iaa.es » Sat Jun 18, 2016 8:13 am

Which is the size of the photographed area??

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Re: APOD: Sputnik Planum vs. Krun Macula (2016 Jun 18)

Post by jhall230@comcast.net » Sat Jun 18, 2016 11:58 am

really is there this much light on pluto's surface???

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Re: APOD: Sputnik Planum vs. Krun Macula (2016 Jun 18)

Post by Chris Peterson » Sat Jun 18, 2016 2:06 pm

jhall230@comcast.net wrote:really is there this much light on pluto's surface???
You can't judge the amount of light on a scene from a photograph. Consider this nighttime image made on Earth, lit only by the Moon:
And on Pluto, the Sun is almost 500 times brighter than the full moon on Earth.

Astronomical images almost always have their contrast adjusted so that the darkest pixel is rendered as black and the brightest as white, giving a full range of intensities and allowing our eyes to see the maximum detail. And in fact, our eyes do something similar- which is why the Moon appears white at night, despite being no brighter than freshly poured asphalt.
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Re: APOD: Sputnik Planum vs. Krun Macula (2016 Jun 18)

Post by Guest2 » Sat Jun 18, 2016 4:03 pm

How can the UV be strong enough to cause significant reaction at that distance and temperature? Does not seem likely.

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Re: APOD: Sputnik Planum vs. Krun Macula (2016 Jun 18)

Post by Chris Peterson » Sat Jun 18, 2016 4:32 pm

Guest2 wrote:How can the UV be strong enough to cause significant reaction at that distance and temperature? Does not seem likely.
The temperature is largely irrelevant. And all the distance does is reduce the intensity, not the energy of the photons that cause the reactions. The reduced intensity simply means the reaction rate is reduced. The Sun at Pluto is about 1500 times fainter than it is at Earth. So figure, to a first approximation, that photolytic reactions will occur about 1500 times slower. In reality, the number is probably a lot smaller than this, since the Earth's atmosphere considerably reduces the amount of UV that makes it to the surface. So given Pluto's fairly stable surface and lack of significant weathering (except for space weathering), it's easy to understand how solar UV radiation can alter the surface, particularly over geological time spans.
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Re: APOD: Sputnik Planum vs. Krun Macula (2016 Jun 18)

Post by DavidLeodis » Sun Jun 19, 2016 11:47 am

Another great photo of the fascinating place that Pluto is. I like Pluto :). OK, it may be a bit chilly and not so good air but nothing that a good down-filled anorak and some oxygen tanks won't cure! :wink:

PS. "Pluto's pitted plains" is almost a tongue twister!

PPS. Krun Macula sounds like it should be the name of a Sci-Fi character!

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Re: APOD: Sputnik Planum vs. Krun Macula (2016 Jun 18)

Post by Evermore » Mon Jun 20, 2016 8:29 pm

Chris Peterson wrote:
jhall230@comcast.net wrote:really is there this much light on pluto's surface???
You can't judge the amount of light on a scene from a photograph. Consider this nighttime image made on Earth, lit only by the Moon:
And on Pluto, the Sun is almost 500 times brighter than the full moon on Earth.

Astronomical images almost always have their contrast adjusted so that the darkest pixel is rendered as black and the brightest as white, giving a full range of intensities and allowing our eyes to see the maximum detail. And in fact, our eyes do something similar- which is why the Moon appears white at night, despite being no brighter than freshly poured asphalt.
'...the sun is almost 500 times brighter than the full moon on earth ...' that's a nice bit of information, and on earth sailors of old wrote things like '.. day and night are about the same with a full moon ..' On earth even with no moon the stars shine a lot of light, it just takes time for the eyes to adjust.

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Re: APOD: Sputnik Planum vs. Krun Macula (2016 Jun 18)

Post by neufer » Mon Jun 20, 2016 9:07 pm

Chris Peterson wrote:
Guest2 wrote:
How can the UV be strong enough to cause significant reaction at that distance and temperature? Does not seem likely.
The temperature is largely irrelevant. And all the distance does is reduce the intensity, not the energy of the photons that cause the reactions. The reduced intensity simply means the reaction rate is reduced. The Sun at Pluto is about 1500 times fainter than it is at Earth. So figure, to a first approximation, that photolytic reactions will occur about 1500 times slower. In reality, the number is probably a lot smaller than this, since the Earth's atmosphere considerably reduces the amount of UV that makes it to the surface. So given Pluto's fairly stable surface and lack of significant weathering (except for space weathering), it's easy to understand how solar UV radiation can alter the surface, particularly over geological time spans.
http://pluto.jhuapl.edu/News-Center/News-Article.php?page=20150703-2 wrote: <<What color is Pluto? The answer, revealed in the first maps made from New Horizons data, turns out to be shades of reddish brown.

Experts have long thought that reddish substances are generated as a particular color of ultraviolet light from the sun, called Lyman-alpha (UVC = 121.567 nm), strikes molecules of the gas methane (CH4) in Pluto's atmosphere, powering chemical reactions that create complex compounds called tholins. The tholins drop to the ground to form a reddish "gunk."

Recent measurements with New Horizons' Alice instrument reveal that a diffuse Lyman-alpha glow falling on Pluto from all directions in interplanetary space is strong enough to produce almost as much tholin as the direct rays of the sun. "This means Pluto's reddening process occurs even on the night side where there's no sunlight, and in the depths of winter when the sun remains below the horizon for decades at a time," said New Horizons co-investigator Michael Summers, George Mason University, Fairfax, Virginia.>>
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