Starship Asterisk*

by **BMAONE23** » Fri Nov 20, 2009 6:51 pm

I don't think that Phobos or Deimos were once moons of any other larger gaseous planetary bodies. They would have been imparted with significant kinetic energy to have been driven away from the larger gravity wells and would have been carrying too much kinetic energy to have been captured by the comparatively minuscule Martian gravity well.
It is much more likely that both moons were created at the time of the Hellas Basin impact than being captured bodies from other external sources

From WIKI
"The origin of the Martian moons is still controversial. The main hypotheses are that they formed either by capture or by accretion. Because of the similarity to the composition of C- or D-type asteroids, one hypothesis is that the moons may be objects captured into Martian orbit from the asteroid belt, with orbits that have been circularized either by atmospheric drag or tidal forces. Capture also requires dissipation of energy. The current Mars atmosphere is too thin to capture a Phobos-sized object by atmospheric braking. Geoffrey Landis has pointed out that the capture could have occurred if the original body was a binary asteroid that separated due to tidal forces. The main alternative hypothesis is that the moons accreted in the present position. Another hypothesis is that Mars was once surrounded by many Phobos- and Deimos-sized bodies, perhaps ejected into orbit around it by a collision with a large planetesimal."

by **astrolabe** » Sat Nov 14, 2009 11:11 pm

Hello All,

It got punched right in the kisser by it's brother, Deimos.

by **Storm_norm** » Sat Nov 14, 2009 6:33 am

if I were to just open my eyes and look at the picture for 10 seconds and close them again. I would swear the orange patches were rust and i was looking at some deformed piece of iron.

by **kovil** » Fri Nov 13, 2009 4:54 pm

Подумал я, если вы были риторическими или серьезный.

LOL

Как говорят в Шотландии, когда кто-то играет волынка плохо ", кто-то сжимая кошка снова".

А во Франции, сокращенный вариант определения ноу-хау является: "Если он может продолжить работу, это ноу-хау".

[as a translator of english to russian, google sucks]

by **apodman** » Fri Nov 13, 2009 4:22 pm

Какая разница между аккордеоном и кошкой?

Только стоимость, оба они делают те же виды звуков при сжатии их.

---

Что такое определение джентльмена?

Кто-то, кто знает, как играть на баяне, но не делает.

by **kovil** » Fri Nov 13, 2009 4:06 pm

Au contraire,

I suspect Phobos was 'combed' by a giant space comb,

akin to in the film "Spaceballs" when Darth Helmet ordered his men to 'comb the desert' in search for Princess Vespa, Fluke Starbucker, Barf and Lonestar !

(I'm afraid I must defer to Neufer and his amazing talents, to find and post the classic photo of Helmet's men 'combing the desert' !)
This is as close as I got: http://www.flickr.com/photos/lambj/1066571404/
http://media.photobucket.com/image/comb ... 12.jpg?o=1

Bawper, Is this actually a question ? << Would someone please show me how to use this computer's Russian translation composition faculty? >>

by **Bawper** » Fri Nov 13, 2009 2:53 pm

Phobos was a giant accordian, expanding and squeezing through gravity before and after apogees and perogees (if that's how those words are spelled) creating the cratered lines by venting steam from compressed ice layers. Nothing complicated about those lines at all.

by **Tarree** » Wed Nov 11, 2009 11:23 pm

That gives me an idea. The paired craters are hoof prints left by cavorting spacecows.

by **bystander** » Wed Nov 11, 2009 6:54 pm

Tarree wrote:If the moderator is a giant space cow, can we post about space cow abductions?

No, we don't want anyone getting ideas.

by **Tarree** » Wed Nov 11, 2009 6:39 pm

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.

by **grump** » Tue Nov 10, 2009 5:06 am

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.

by **JohnD** » Mon Nov 09, 2009 11:18 am

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

by **NoelC** » Mon Nov 09, 2009 5:41 am

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

by **neufer** » Sun Nov 08, 2009 3:16 pm

rstevenson wrote:
neufer wrote: 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).

by **rstevenson** » Sun Nov 08, 2009 1:13 pm

Yes, looks like they would help.

I want them!

Rob

by **apodman** » Sun Nov 08, 2009 12:54 pm

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

by **rstevenson** » Sun Nov 08, 2009 12:42 pm

neufer wrote: 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

by **neufer** » Sun Nov 08, 2009 12:18 pm

jpoore wrote: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.

by **JohnD** » Sun Nov 08, 2009 11:40 am

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

by **Chris Peterson** » Sun Nov 08, 2009 4:04 am

Frenchy wrote: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.

by **Frenchy** » Sun Nov 08, 2009 3:26 am

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?

by **jpoore** » Sun Nov 08, 2009 1:28 am

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?

by **Chris Peterson** » Sat Nov 07, 2009 11:37 pm

Frenchy wrote: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"?

by **Frenchy** » Sat Nov 07, 2009 10:35 pm

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

by **QuBit** » Sat Nov 07, 2009 9:38 pm

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…

Starship Asterisk*

Stickney Crater (APOD 2009 November 7)

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