APOD: Stickney Crater (2018 May 05)

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APOD: Stickney Crater (2018 May 05)

Post by APOD Robot » Sat May 05, 2018 4:05 am

Image Stickney Crater

Explanation: Stickney Crater, the largest crater on the martian moon Phobos, is named for Chloe Angeline Stickney Hall, mathematician and wife of astronomer Asaph Hall. Asaph Hall discovered both the Red Planet's moons in 1877. Over 9 kilometers across, Stickney is nearly half the diameter of Phobos itself, so large that the impact that blasted out the crater likely came close to shattering the tiny moon. This stunning, enhanced-color image of Stickney and surroundings was recorded by the HiRISE camera onboard the Mars Reconnaissance Orbiter as it passed within some six thousand kilometers of Phobos in March of 2008. Even though the surface gravity of asteroid-like Phobos is less than 1/1000th Earth's gravity, streaks suggest loose material slid down inside the crater walls over time. Light bluish regions near the crater's rim could indicate a relatively freshly exposed surface. The origin of the curious grooves along the surface is mysterious but may be related to the crater-forming impact.

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Re: APOD: Stickney Crater (2018 May 05)

Post by Boomer12k » Sat May 05, 2018 8:15 am

Wonderful Image...and intriguing...

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Re: APOD: Stickney Crater (2018 May 05)

Post by orin stepanek » Sat May 05, 2018 10:45 am

Wondering the composition of the Silvery material? :shock:
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Re: APOD: Stickney Crater (2018 May 05)

Post by Ann » Sat May 05, 2018 11:30 am

orin stepanek wrote:
Sat May 05, 2018 10:45 am
Wondering the composition of the Silvery material? :shock:
(Relatively) fresh ice?

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Re: APOD: Stickney Crater (2018 May 05)

Post by barobins@telusplanet.net » Sat May 05, 2018 12:43 pm

What would happen to Earth's moon if a large object similar to what hit Phobos hit our Moon?? Would that cause tidal waves on Earth?? Would we be in the path of any debris that would be dislodged from the Moon? IF we have a colony on the Moon would we have time to get them off and out of danger??

heehaw

Re: APOD: Stickney Crater (2018 May 05)

Post by heehaw » Sat May 05, 2018 1:51 pm

barobins@telusplanet.net wrote:
Sat May 05, 2018 12:43 pm
What would happen to Earth's moon if a large object similar to what hit Phobos hit our Moon?? Would that cause tidal waves on Earth?? Would we be in the path of any debris that would be dislodged from the Moon? IF we have a colony on the Moon would we have time to get them off and out of danger??
An academic question, in your lifetime and mine: https://en.wikipedia.org/wiki/Sentry_(m ... ng_system)

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Re: APOD: Stickney Crater (2018 May 05)

Post by Chris Peterson » Sat May 05, 2018 2:07 pm

orin stepanek wrote:
Sat May 05, 2018 10:45 am
Wondering the composition of the Silvery material? :shock:
The surface of Phobos consists of rock- primarily silicates. There may be ice in the interior, but there is no ice on the surface and the regolith is not hydrated. The reflectivity of the surface material is very low- Phobos is really a lump of coal in appearance. The outer few meters is weathered regolith, which is naturally dark. Anything which exposes underlying material will create lighter areas. That includes impacts and landslides. The image has been enhanced so that we can see detail and structure. The natural albedo range, which is low, has been stretched to approximately 100%. In other words, what you're seeing as "silvery" may be as dark as fresh asphalt in reality.
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Re: APOD: Stickney Crater (2018 May 05)

Post by Chris Peterson » Sat May 05, 2018 2:10 pm

barobins@telusplanet.net wrote:
Sat May 05, 2018 12:43 pm
What would happen to Earth's moon if a large object similar to what hit Phobos hit our Moon?? Would that cause tidal waves on Earth?? Would we be in the path of any debris that would be dislodged from the Moon? IF we have a colony on the Moon would we have time to get them off and out of danger??
Keep in mind that the object which hit Phobos only created a crater 9 km across. Such objects hit the Moon every few thousand years. That has no effect on Earth at all. A collision of that size might produce a few lunar meteorites on Earth. No tidal effects, no impacts. Nor would it cause any problems for a colony on the Moon unless the impact was very close to that colony.
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Re: APOD: Stickney Crater (2018 May 05)

Post by Rick357 » Sat May 05, 2018 2:23 pm

Ablation. The 'moon' went through atmosphere oriented so the left side was exposed to the atmospheric erosion - the crater rim is significantly rounded with trailing tendrils of ablative channels, and the right side was protected in the lee of direction of the motion - the crater rim is sharp and pristine looking.

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Re: APOD: Stickney Crater (2018 May 05)

Post by Chris Peterson » Sat May 05, 2018 2:25 pm

Rick357 wrote:
Sat May 05, 2018 2:23 pm
Ablation. The 'moon' went through atmosphere oriented so the left side was exposed to the atmospheric erosion - the crater rim is significantly rounded with trailing tendrils of ablative channels, and the right side was protected in the lee of direction of the motion - the crater rim is sharp and pristine looking.
Not likely. This is not a solid body, but some sort of rubble pile with a few meters of fine powder on its surface. And it couldn't have encountered an atmosphere in the last tens of millions of years or longer, meaning most evidence of such an encounter would have long since weathered away.
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Re: APOD: Stickney Crater (2018 May 05)

Post by neufer » Sat May 05, 2018 4:50 pm

http://maia.usno.navy.mil/women_history/hall.html wrote: The Contributions of Women to the United States Naval Observatory: The Early Years.

<<One of the greatest obstacles to professional success for a woman in science in the late 19th and early 20th century, was the pressure put on her by society. Ancient folklore and even the current "scientific" research concluded that women should avoid education. One such "scientific study" conducted by Dr. Edward Clark of Harvard in the late nineteenth century concluded that the intellectual development of a woman would proceed only at the sacrifice of her reproductive organs. If a woman did pursue an education and a career, then married, she was expected to resign her position to become a full-time wife and mother. If an educated woman married a man in the scientific community she was expected to resign her position in order to assist her husband in his career. In fact, the career of a male scientist was usually greatly enhanced by assistance from his wife in the same field, although the woman received little or no credit and compensation for their contributions.

A prime example of this occurred at the USNO with one of our most prominent astronomers, Asaph Hall who discovered the two moons of Mars. Hall was fortunate enough to marry Chloe Angeline Stickney, a woman who had been his mathematics professor in college. During their days together as teacher and student, Hall and his classmates would devise questions and problems that they were convinced Miss Stickney could not solve, yet she never failed to solve them. Angeline Stickney gave up her career to marry Asaph Hall, she took an active interest in her husband's career. In fact it was she who petitioned Captain Gilliss via letter to promote her husband to Professor of Mathematics. Captain Gilliss embraced this suggestion, replying to Mrs. Hall that she could hereafter address her husband as "Professor" Hall. Asaph Hall himself acknowledged the contribution his wife made to his success in astronomy when speaking of his discovery of Demios and Phobos; "The chance of finding a satellite appeared to be very slight, so that I might have abandoned the search had it not been for the encouragement of my wife." However Mr. Hall drew the line when Mrs. Hall demanded a man's wage while she assisted her husband in his computations, when he refused her, she refused to continue that work.>>
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Re: APOD: Stickney Crater (2018 May 05)

Post by Cousin Ricky » Sat May 05, 2018 5:30 pm

APOD Robot wrote:
Sat May 05, 2018 4:05 am
The origin of the curious grooves along the surface is mysterious but may be related to the crater-forming impact.
The grooves do not appear to radiate from Stickney, however; at least not in this photo. Another hypothesis that I’m aware of is that Phobos is getting uncomfortably close to the Roche limit, and the grooves are an effect of tidal stress. Probably more likely is that, since the radiant coincides with Phobos’ leading apex, they are due to multiple smaller impacts over the eons [citation].

JOHN MIOTTEL

Re: APOD: Stickney Crater (2018 May 05)

Post by JOHN MIOTTEL » Sat May 05, 2018 5:40 pm

I finally asked myself what caused the craters - there is no residual impact object like a big rock - I guess the impact object must be ice chunks ??

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LIMTOC: The Stickey Crater

Post by neufer » Sat May 05, 2018 5:58 pm

https://en.wikipedia.org/wiki/Stickney_(crater) wrote:
<<Stickney has a smaller crater within it, about 2 km in diameter, resulting from a later impact.
In 2006 it was given the name LIMTOC, after a character in Gulliver's Travels.

..................................................................................................................
. Gulliver's Travels, by Jonathan Swift Chapter VII.

<<This lord, in conjunction with Flimnap the high-treasurer, whose enmity against you is notorious on account of his lady, LIMTOC the general, Lalcon the chamberlain, and Balmuff the grand justiciary, have prepared articles of impeachment against you, for treason and other capital crimes.”

“’Articles of Impeachment against QUINBUS FLESTRIN, (the Man-Mountain.)

ARTICLE I: “’Whereas, by a statute made in the reign of his imperial majesty Calin Deffar Plune, it is enacted, that, whoever shall make water within the precincts of the royal palace, shall be liable to the pains and penalties of high-treason; notwithstanding, the said Quinbus Flestrin, in open breach of the said law, under colour of extinguishing the fire kindled in the apartment of his majesty’s most dear imperial consort, did maliciously, traitorously, and devilishly, by discharge of his urine, put out the said fire kindled in the said apartment, lying and being within the precincts of the said royal palace, against the statute in that case provided, etc. a.>>
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Re: APOD: Stickney Crater (2018 May 05)

Post by starchyld » Fri May 25, 2018 8:45 pm

blue hued exposed rock probably indicate friction with particles of the troposhere of mars. phobos orbit about mars is decaying. in a few years phobos will likely fall apart into large fragments and plunge into atmosphere of mars in a fiery blaze over an extended period of time. merge of phobos with mars will signal a new beginning.

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Re: APOD: Stickney Crater (2018 May 05)

Post by Chris Peterson » Fri May 25, 2018 9:51 pm

starchyld wrote:
Fri May 25, 2018 8:45 pm
in a few years phobos will likely fall apart into large fragments and plunge into atmosphere of mars in a fiery blaze over an extended period of time.
Well, in a few tens of millions of years.
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Re: APOD: Stickney Crater (2018 May 05)

Post by neufer » Fri May 25, 2018 10:26 pm

starchyld wrote:
Fri May 25, 2018 8:45 pm

blue hued exposed rock probably indicate friction with particles of the troposhere of mars.
  • Not the atmosphere ... and DEFINITELY NOT the "troposhere."
https://en.wikipedia.org/wiki/Atmosphere_of_Mars wrote:

Curiosity's view of the Mars moons
Phobos passing in front of Deimos
in real-time (1 August 2013).
.
Mars's atmosphere is composed of the following layers:

Exosphere: Typically stated to start at 200 km and higher, this region is where the last wisps of atmosphere merge into the vacuum of space. There is no distinct boundary where the atmosphere ends; it just tapers away.

Upper atmosphere, or thermosphere: A region with very high temperatures, caused by heating from the Sun. Atmospheric gases start to separate from each other at these altitudes, rather than forming the even mix found in the lower atmospheric layers.

Middle atmosphere: The region in which Mars's jetstream flows.

Lower atmosphere/ "troposphere" :
A relatively warm region affected by heat from airborne dust and from the ground.>>
https://en.wikipedia.org/wiki/Phobos_(moon) wrote:
<<Phobos orbits 6,000 km from the Martian surface, closer to its primary body than any other known planetary moon. It is indeed so close that it orbits Mars much faster than Mars rotates, and completes an orbit in just 7 hours and 39 minutes.

Tidal deceleration is gradually decreasing the orbital radius of Phobos by 2 meters every one hundred years. Scientists estimate that Phobos will be destroyed in approximately 30–50 million years, with one study's estimate being about 43 million years.

Researchers suggest that the grooves are "stretch marks" caused by tidal forces. This idea is based on the model that Phobos is a rubble pile surrounded by a 100 m layer of powdery regolith. Stress fractures calculated for this model line up with the grooves on Phobos. The model is supported with the discovery that some of the grooves are younger than others, implying that the process that produces the grooves is ongoing. Given Phobos's irregular shape and assuming that it is a pile of rubble, it will eventually break up when it reaches approximately 2.1 Mars radii [~3,750 km from the Martian surface].

When Phobos is eventually torn apart by tidal forces, it is likely that a fraction of the debris will form a planetary ring around Mars. This ring may last for between one million and one hundred million years.>>
Art Neuendorffer