Stickney Crater (APOD 2009 November 7)

[neufer]

http://apod.nasa.gov/apod/ap091107.html

hloe [A]ngeline tickney [H]all (November 1, 1830 – July 3, 1892) suffragist, abolitionist, and mathematician, was the wife of astronomer Asaph Hall. She did not use her first name and so is also known as Angeline Stickney Hall. Though poor, Angeline Stickney was able to attend Central College in McGrawville, New York with help from her sister Ruth, and through teaching at the college. She majored in science and mathematics, including courses in calculus and mathematical astronomy. Central College was a progressive school where students of modest means, including women and free African Americans could earn a college degree. It was here that she became passionate about the causes of women's suffrage and the abolition of slavery.

At Central College, Asaph Hall (October 15, 1829 – November 22, 1907) took her courses in geometry and German, and she gave up her career to marry him at Elkhorn, Wisconsin on March 31, 1856. She is believed to have helped him with mathematical calculations early in his career. She encouraged him to continue his search for satellites of Mars when he was ready to give up, and he successfully discovered Phobos and Deimos.



Hall home-schooled all four of her children and all attended Harvard University. Her third son Angelo Hall, a Unitarian minister, wrote her biography. The oldest son, also named Asaph, was born on October 6, 1859 and served as director of Detroit Observatory from 1892 to 1905. Other sons were named Samuel (second son) and Percival (fourth son); Percival Hall (1872–1953) was the second president of Gallaudet University from 1910 to 1946 (he himself was not deaf).

She died at North Andover, Massachusetts at age 61.>>

--------------------------------------------
Personal note: My grandmother (Esther Sinn)'s Bryn Mawr _Lamb's Calculus_ book
is more sophisticated than the calculus book I myself used at MIT.

[orin stepanek]

Some how the crater doesn't look much like an impact crater! I wonder how it was formed.

Orin

[DanEspen]

Those grooves remind me of something I saw underwater in the Cayman islands.
The grooves were formed by rocks being pushed back and forth by the waves.
I wonder if there is enough gravity from Mars to move rocks on the moons surface.

[bystander]

Some how the crater doesn't look much like an impact crater! I wonder how it was formed.

None of the craters look much like what I expect impact craters to look like. IMHO, it has to do with the low surface gravity (ejecta blasted into space) and the lack of weathering.

[apodman]

Looks like the false color photograph the dentist took of my decayed molar.

[neufer]

<<Phobos's unusually close orbit around its parent planet produces some unusual effects. Phobos orbits Mars below the synchronous orbit radius, meaning that it moves around Mars faster than Mars itself rotates. Therefore it rises in the west, moves comparatively rapidly across the sky (in 4 h 15 min or less) and sets in the east, approximately twice each Martian day (every 11 h 6 min). Phobos's phases, inasmuch as they can be observed from Mars, take 0.3191 days (Phobos's synodic period) to run their course, a mere 13 seconds longer than Phobos's sidereal period.

It is possible that Stickney is large enough to be seen with the naked eye from the surface of Mars. It is located at the middle of the western edge of Phobos's face, on the Mars-facing side.

• Phobos transits Sun, as seen by Mars Rover Opportunity
  

Stickney has a smaller crater within it, about 2 km (1.2 mi) in diameter, resulting from a later impact. In 2006 it was given the name Limtoc, after a character in Gulliver's Travels.>>

<<Lilliput is ruled by an emperor, whose two sons are Admiral Bolgolam of the Navy and General Limtoc, chief commander of the army. They hope to make use of [Giant Gulliver] as a weapon of war, and are disgusted by his independendence, while Treasurer Flimnap frets over what he consumes. The Emperor is merely amused by the Man Mountain, his empress repulsed by him (although gazing up at his nether regions during a parade, she utters a cry of "Colossus!"), and scroungers Clustril and Drunlo hope tro acquire riches and court favor through him. The Lilliputians have been at war with their equally diminutive neighbors in Blefescu for generations, stemming from a dispute over which end of the egg should be broken when breakfasting.>>

• ___ *Limtoc Bolgolam*
  ______ {anagram}
  ___ *Ill Combat Gloom*

Gen. Limtoc: Yesterday we gave him enough to feed a regiment for a week. Now he says he's hungry again!
..................................
[the Emperor, his sons, General Limtoc and Admiral Bolgolam, Clustril and other s are in the Lilliputian campaign room, discussing Gulliver's 'inventive' way of extinguishing a fire]

Adm. Bolgolam: This is an outrage! He made water in the royal grounds! It's a treasonable offence!

Emperor of Lilliput: But he saved the Empress' life!

Gen. Limtoc: At what cost?
Our stepmother may never go out in public again, convinced that she's the laughing stock of Lilliput!

- from Gulliver's Travels (1996) (TV)

[Star*Hopper]

Came for the "...but I see Egyptian hieroglyphics draped over the crater's rim -- CONSPIRACY!!!" comments.
Leaving less than fulfilled.


~S*H

[apodman]

Came for the "...but I see Egyptian hieroglyphics draped over the crater's rim -- CONSPIRACY!!!" comments.
Leaving less than fulfilled.


~S*H

Some things are so obvious that no comment is necessary. But it does look a lot like our friend the owl-spider.

[neufer]

Some things are so obvious that no comment is necessary.
But it does look a lot like our friend the owl-spider.

Which just turned out to be Ardipithecus ramidus after all:

[QuBit]

Interesting Picture – in Colour

Looks like Phobos is one GIANT lump of Water Ice !! – A few trillion tons…
– Covered with a bit of Mars dust…

Could be rather useful in years to come…

[Frenchy]

What effect would a surge of black body radiation have on an astronomical object such as Phobos?

[Chris Peterson]

What effect would a surge of black body radiation have on an astronomical object such as Phobos?

What exactly is a "surge of blackbody radiation"?

[jpoore]

Could one of Ardi's grandchildren, finding himself on Phobos, leap off? If not, how long would it take to come back down in 1/1000 G?

[Frenchy]

What I mean by a "surge of black body radiation" is all forms of electromagnetic radiation minus the visible component of the electromagnetic spectrum. Black body radiation would most likely be produced by an astronomical object emitting mostly radio, x-ray, and gamma ray frequencies.

Do any objects in space emit just those frequencies?

[Chris Peterson]

What I mean by a "surge of black body radiation" is all forms of electromagnetic radiation minus the visible component of the electromagnetic spectrum. Black body radiation would most likely be produced by an astronomical object emitting mostly radio, x-ray, and gamma ray frequencies.

Do any objects in space emit just those frequencies?

No blackbody sources. Blackbody radiation just describes the spectral distribution of radiation from a thermal source. Most hot objects- including astronomical ones- produce a radiative output that is approximated by a blackbody model. It doesn't exclude visible light- in fact, any blackbody source produces photons in the visible range. Phobos is strongly irradiated by blackbody radiation from the Sun, which peaks in the visible part of the spectrum.

[JohnD]

Back to the grooves.

Not anything to do with Stickney. Other views of Phobos show that they are not concentric on the crater, but remarkably parallel across the moon and post date it, as they appear inside the crater. See this Viking pic: http://www.mira.org/fts0/planets/097/im ... ik1_r1.jpg
Some have compared them to geological strata, but that's ridiculous.
IMHO, they are crater chains. That some of them are made up of lines of confluent craters is clearly seen in this HiRise pic:
http://apod.nasa.gov/apod/ap080414.html
And before anyone asks if I'm arguing in favour of past interplanetary warfare, crater chains are a common, naturally occcuring fetaure of many Solar System satellites!

JOhn

[neufer]

Could one of Ardi's grandchildren, finding himself on Phobos, leap off?
If not, how long would it take to come back down in 1/1000 G?

A general rule might be that if you can jump h feet high (in a sqrt(h)/2 second ride) on earth
then you can jump ~ 4*h/g feet high (in a sqrt(h)/g second ride) on a small planetoid
where g is the planetoid's surface gravity in G's.

(I am neglecting here the need for a heavy space suit like that which hampered Apollo astronauts.)

So an average healthy adult human might jump some 4000 ft high (in a 1000 second ride) off of Phobos
but this is not nearly high enough to escape Phobos's gravity.

I would think that some of the earth's best athletes could probably escape the gravity of Deimos
but they would definitely require the help of a good trampoline to escape the gravity of Phobos.

Of course this would just put them into an orbit around Mars which would sooner or later crash land them back on Deimos or Phobos, respectively.

[rstevenson]

A general rule might be that if you can jump h feet high (in a sqrt(h)/2 second ride) on earth
then you can jump ~ 4*h/g feet high (in a sqrt(h)/g second ride) on a small planetoid
where g is the planetoid's surface gravity in G's.

One issue I saw mentioned in another on-line discussion of this is that our Earth-evolved muscles wouldn't be able to bring their full power to bear when we try to jump off an object of very low mass -- something to do with our body lifting off the surface before the full tension of our muscle-springs can be released. I'm not sure if that's true, and it may be amenable to practice if it is, but I thought I'd mention it as a complication. As usual, I volunteer to go up and test out the idea personally.

Rob

[apodman]

These would need to be compressed, locked, and then released in sync with the jump.

[rstevenson]

Yes, looks like they would help.

I want them!

Rob

[neufer]

A general rule might be that if you can jump h feet high (in a sqrt(h)/2 second ride) on earth
then you can jump ~ 4*h/g feet high (in a sqrt(h)/g second ride) on a small planetoid
where g is the planetoid's surface gravity in G's.

One issue I saw mentioned in another on-line discussion of this is that our Earth-evolved muscles wouldn't be able to bring their full power to bear when we try to jump off an object of very low mass -- something to do with our body lifting off the surface before the full tension of our muscle-springs can be released.

Nothing prevents one from using fixed handles on the ground to build up that full tension in a crouch position before "blasting off."

Note: The factor of 4 in the above equation comes from the assumption that one's "blasting off" stretching acceleration can be quadrupled simply by not having to perform it against earth's gravity. This is roughly equivalent to the Ares X 1 being able to initially accelerate at 1.35 G's from Phobos as compared to just 0.35 G's from the earth. For top athletes this advantage factor is probably only 2 or 3. (Contrariwise, top athletes could probably jump a little under Jupiter gravity conditions while the rest of us wouldn't be able to get up off the floor).

[NoelC]

Looking at the high resolution image (click through the APOD image) I see that some of the lines, at least, are trenches. One, very near the left edge of the photo, appears to have an object in it - a rock or something.

I like DanEspen's theory that rocks are rolling around on the dusty surface. Perhaps there were some low velocity collisions after one of the impacts blew some material off the surface...

-Noel

[JohnD]

Noel,
Look up the surface gravity on Phobos.
It's 2 to 8 MILLIMETERS per second (varies due to shape on moon)
There's no way that rocks could roll.
They would fly.

John

[grump]

I like the rolling rocks idea. Gravity is low, but inertia is inertia and is related to mass, not 'weight'.

Another idea is that the lines were caused by abrasion from the cargo net that was used to tow it into place during the battle between the Martians and the Europese (from the Jovian moon) (not that they called themselves that) about 472,000 earth years ago. The Europese set up a base there from which to dominate near-Martian space, but they hadn't counted on the Martians using their until then secret dark matter projector after conventional ballistic weapons (see the many pock marks still visible) failed to have any real effect. One blast was all it took, and the rest is history.

[Tarree]

Did anybody else notice that the many small craters are frequently arranged in pairs of generally the same size?

In the upper right of the lower left quadrant is a brown crater with brown splattering down. It's pair is just to the right and up of it, a blue crater with brown drool. To the right of that are two paired blue craters. Above those on the lip is one blue crater, with just to the right on the opposite slope is it's blue pair, seen edge on. To the right on the brown lip are two craters and to the right on the edge of the picture are another pair. By the second biggest crater (in the big crater) are several pairs, notably to the right and "below" it. On the lip above the first crater I mentioned above are two small blue craters. To the right and left of them are two more small pairs. If you look across the bottom of the picture it is easy to see at least 4 more pair of craters. There are more.