Starship Asterisk*

jhall230@comcast.net wrote:really is there this much light on pluto's surface???

Guest2 wrote:How can the UV be strong enough to cause significant reaction at that distance and temperature? Does not seem likely.

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:

Click to view full size image

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.

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:

[size=135][b][color=#BF00BF]All UVC is blocked by diatomic oxygen (from 100–200 nm) or by ozone (triatomic oxygen) (200–280 nm) in Earth's atmosphere.[/color] [color=#00BF00]The ozone layer then blocks most UVB (from 280–315 nm).[/color][/b][/size]

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<<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.>>

APOD Robot wrote: ↑Sat Jun 18, 2016 4:05 am Sputnik Planum vs. Krun Macula

Explanation: 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.

• https://www.universetoday.com/152050/tw ... roid-belt/

https://en.wikipedia.org/wiki/269_Justitia wrote:
<<Justitia (minor planet designation: 269 Justitia) is a fairly sizeable (53.6 km) main belt asteroid (semi-major axis: 2.61515 AU). It was discovered by Johann Palisa on 21 September 1887 in Vienna and named after Justitia, the Greek goddess of justice. As discovered in 2021, the asteroid has a very red color due to tholin coating, similar to trans-Neptunian objects. It is therefore thought to have formed in the outer Solar System despite its current orbit within the asteroid belt.>>

https://en.wikipedia.org/wiki/203_Pompeja wrote:
<<Pompeja (minor planet designation: 203 Pompeja) is a quite large (116 km) main-belt asteroid (semi-major axis: 2.7367 AU). It was discovered by C. H. F. Peters on September 25, 1879, in Clinton, New York, and named after Pompeii, the Roman town destroyed in volcanic eruption in AD 79. As discovered in 2021, the asteroid has a very red color due to tholin coating, similar to Trans-Neptunian objects. It is therefore thought to have formed in the outer Solar System despite its current orbit within the asteroid belt.>>