Starship Asterisk*

APOD Robot wrote:
featured here in natural color

At the bottom of most craters lies some type of unknown dark reddish material.

Smithsonian Insider wrote:

Writing in this month’s Astrophysical Journal, Center for Astrophysics astronomers and SWAS team leaders Gary Melnick and Volker Tolls, along with two previous members of the Center for Astrophysics and SWAS community and four colleagues, published summary conclusions from a study of water over a very large area of the sky. They mapped water vapor along a ridge of warm material in the Orion nebula nearly 18 light-years in length.

Ann wrote: ↑Mon May 14, 2018 4:48 am

APOD Robot wrote:
featured here in natural color

It looks grayish to me. Or grayish beige.

bjmb wrote: ↑Mon May 14, 2018 5:00 am "To help find out, the robot Cassini spacecraft now orbiting Saturn ... " didn't cassini crash into saturn in september 2017?

Ann wrote: ↑Mon May 14, 2018 4:48 am
Hyperion is a fascinating moon, if not for its color, at least for its apparent texture. It sure looks like a sponge to me. Maybe it used to belong to some extra-supergiant space monster, who lost his sponge when he was about to take a bath in, oh, the Orion Nebula?

https://insider.si.edu/2011/02/astronomers-examine-location-and-amount-of-water-in-the-orion-nebula/ wrote:
Writing in this month’s Astrophysical Journal, Center for Astrophysics astronomers and SWAS team leaders Gary Melnick and Volker Tolls, along with two previous members of the Center for Astrophysics and SWAS community and four colleagues, published summary conclusions from a study of water over a very large area of the sky. They mapped water vapor along a ridge of warm material in the Orion nebula nearly 18 light-years in length.

And if you're going to take a bath in an 18-light-year-long bath tub, you may certainly need a sponge the size of a moon.

• Hamlet : Act III, scene IV

• The counterfeit presentment of two brothers.
  See, what a grace was seated on this brow;
  Hyperion's curls; the front of Jove himself;
  An eye like Mars, to threaten and command;
  A station like the herald Mercury
  New-lighted on a heaven-kissing hill;
  A combination and a form indeed,
  Where every god did seem to set his seal,
  To give the world assurance of a man:
  This was your husband. Look you now, what follows:
  Here is your husband; like a mildew'd ear,
  Blasting his wholesome brother. Have you eyes?

Catalina wrote: ↑Mon May 14, 2018 6:53 pm
Could the dark material at the bottom of the craters be heavier, denser particles/boulders that have rolled down the walls of the craters under the effect of the moon's weak gravity?

https://en.wikipedia.org/wiki/Hyperion_(moon)#Surface_features wrote:
<<Hyperion's surface is covered with deep, sharp-edged craters that give it the appearance of a giant sponge. Dark material fills the bottom of each crater. The reddish substance contains long chains of carbon and hydrogen and appears very similar to material found on other Saturnian satellites, most notably Iapetus. NASA scientists now believe that the Iapetus dark material is lag (residue) from the sublimation (evaporation) of water ice on the surface, possibly darkened further upon exposure to sunlight.>>

neufer wrote: ↑Mon May 14, 2018 10:19 pm

Catalina wrote: ↑Mon May 14, 2018 6:53 pm
Could the dark material at the bottom of the craters be heavier, denser particles/boulders that have rolled down the walls of the craters under the effect of the moon's weak gravity?

https://en.wikipedia.org/wiki/Hyperion_(moon)#Surface_features wrote:
<<Hyperion's surface is covered with deep, sharp-edged craters that give it the appearance of a giant sponge. Dark material fills the bottom of each crater. The reddish substance contains long chains of carbon and hydrogen and appears very similar to material found on other Saturnian satellites, most notably Iapetus. NASA scientists now believe that the Iapetus dark material is lag (residue) from the sublimation (evaporation) of water ice on the surface, possibly darkened further upon exposure to sunlight.>>

Catalina wrote: ↑Mon May 14, 2018 11:24 pm

neufer wrote: ↑Mon May 14, 2018 10:19 pm

Catalina wrote: ↑Mon May 14, 2018 6:53 pm
Could the dark material at the bottom of the craters be heavier, denser particles/boulders that have rolled down the walls of the craters under the effect of the moon's weak gravity?

https://en.wikipedia.org/wiki/Hyperion_(moon)#Surface_features wrote:
<<Hyperion's surface is covered with deep, sharp-edged craters that give it the appearance of a giant sponge. Dark material fills the bottom of each crater. The reddish substance contains long chains of carbon and hydrogen and appears very similar to material found on other Saturnian satellites, most notably Iapetus. NASA scientists now believe that the Iapetus dark material is lag (residue) from the sublimation (evaporation) of water ice on the surface, possibly darkened further upon exposure to sunlight.>>

Why would the the lag only appear at the bottoms of the craters?

• That might be the warmest part of the moon where sublimation is the strongest.

https://en.wikipedia.org/wiki/Iapetus_(moon)#Two-tone_coloration wrote:
<<NASA scientists now believe that the dark material is lag (residue) from the sublimation (evaporation) of water ice on the surface of Iapetus. Heat absorption by the dark material results in a daytime temperatures of 129 K in the dark Cassini Regio compared to 113 K in the bright regions. The difference in temperature means that ice preferentially sublimates from Cassini Regio, and deposits in the bright areas and especially at the even colder poles. Over geologic time scales, this would further darken Cassini Regio and brighten the rest of Iapetus, creating a positive feedback thermal runaway process of ever greater contrast in albedo, ending with all exposed ice being lost from Cassini Regio. It is estimated that over a period of one billion years at current temperatures, dark areas of Iapetus would lose about 20 meters of ice to sublimation, while the bright regions would lose only 10 centimeters, not considering the ice transferred from the dark regions.

However, a separate process of color segregation would be required to get the thermal feedback started. The initial dark material is thought to have been debris blasted by meteors off small outer moons in retrograde orbits and swept up by the leading hemisphere of Iapetus.>>