APOD: Phobos 360 (2013 Dec 25)

Comments and questions about the APOD on the main view screen.
Post Reply
User avatar
APOD Robot
Otto Posterman
Posts: 5345
Joined: Fri Dec 04, 2009 3:27 am
Contact:

APOD: Phobos 360 (2013 Dec 25)

Post by APOD Robot » Wed Dec 25, 2013 5:06 am

Image Phobos 360

Explanation: What does the Martian moon Phobos look like? To better visualize this unusual object, images from ESA's Mars Express orbiter have been combined into a virtual rotation movie. The rotation is actually a digital illusion -- tidally-locked Phobos always keeps the same face toward its home planet, as does Earth's moon. The above video highlights Phobos' chunky shape and an unusually dark surface covered with craters and grooves. What lies beneath the surface is a topic of research since the moon is not dense enough to be filled with solid rock. Phobos is losing about of centimeter of altitude a year and is expected to break up and crash onto Mars within the next 50 million years. To better understand this unusual world, Mars Express is on course to make the closest flyby ever on Sunday.

<< Previous APOD This Day in APOD Next APOD >>
[/b]

User avatar
Ann
4725 Å
Posts: 13372
Joined: Sat May 29, 2010 5:33 am

Re: APOD: Phobos 360 (2013 Dec 25)

Post by Ann » Wed Dec 25, 2013 6:08 am

Here comes another Christmas bauble, this time with a twist! The cosmic Christmas tree seems to be full of them.

Interesting video! And Merry Christmas, everybody!

Ann
Color Commentator

Boomer12k
:---[===] *
Posts: 2691
Joined: Sun Apr 22, 2007 12:07 am

Re: APOD: Phobos 360 (2013 Dec 25)

Post by Boomer12k » Wed Dec 25, 2013 6:42 am

If you look at Comets...you see many of the similar features...I wonder if Phobos and smaller "moons" are also "captured comets".

Not all ice need be on the surface per se....said of some Comets, and termed more...."Icey Dirtballs", than "dirty snowballs"..."The surface of the nucleus is generally dry, dusty or rocky, suggesting that the ices are hidden beneath a surface crust several metres thick."

Thus a seeming astroidal object, maybe be a comet ONLY when it is close enough to the sun.

I wonder if Phobos is just a captured Asteroid, or such a Comet....


Merry Xmas....one and all,

:---[===] *

Night eyes

Re: APOD: Phobos 360 (2013 Dec 25)

Post by Night eyes » Wed Dec 25, 2013 8:56 am

Seasons greetings to all you commenters. Your wit and knowledge is is an added pleasure to the posted APOD nightly viewing that this insomniac entertains herself with.

Boomer12k
:---[===] *
Posts: 2691
Joined: Sun Apr 22, 2007 12:07 am

Re: APOD: Phobos 360 (2013 Dec 25)

Post by Boomer12k » Wed Dec 25, 2013 1:34 pm

Are those REINDEER TRACKS?????


:---[===] *

User avatar
rstevenson
Quis custodiet ipsos custodes?
Posts: 2704
Joined: Fri Mar 28, 2008 1:24 pm
Location: Halifax, NS, Canada

Re: APOD: Phobos 360 (2013 Dec 25)

Post by rstevenson » Wed Dec 25, 2013 2:57 pm

See also this APOD, which has been repeated a couple times since. Phobos is a very interesting little moon.

Rob

User avatar
Chris Peterson
Abominable Snowman
Posts: 18112
Joined: Wed Jan 31, 2007 11:13 pm
Location: Guffey, Colorado, USA
Contact:

Re: APOD: Phobos 360 (2013 Dec 25)

Post by Chris Peterson » Wed Dec 25, 2013 3:21 pm

APOD Robot wrote:The rotation is actually a digital illusion -- tidally-locked Phobos always keeps the same face toward its home planet, as does Earth's moon.
No, this is wrong, and perpetuates a misunderstanding about the nature of tidal locking. In fact, Phobos rotates with a period of 8 hours. With tidally locked bodies, the illusion is that they don't rotate.
Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
https://www.cloudbait.com

User avatar
Coil_Smoke
Ensign
Posts: 83
Joined: Sun Nov 17, 2013 7:57 am

Re: APOD: Phobos 360 (2013 Dec 25)

Post by Coil_Smoke » Wed Dec 25, 2013 3:31 pm

Chris Peterson wrote:
APOD Robot wrote:The rotation is actually a digital illusion -- tidally-locked Phobos always keeps the same face toward its home planet, as does Earth's moon.
No, this is wrong, and perpetuates a misunderstanding about the nature of tidal locking. In fact, Phobos rotates with a period of 8 hours. With tidally locked bodies, the illusion is that they don't rotate.
A "tidally Locked" satellite rotates once every complete orbit. How this series of images was captured is a good question. Merry Christmas...C_S

User avatar
Chris Peterson
Abominable Snowman
Posts: 18112
Joined: Wed Jan 31, 2007 11:13 pm
Location: Guffey, Colorado, USA
Contact:

Re: APOD: Phobos 360 (2013 Dec 25)

Post by Chris Peterson » Wed Dec 25, 2013 3:44 pm

Coil_Smoke wrote:A "tidally Locked" satellite rotates once every complete orbit. How this series of images was captured is a good question.
Mars Express is in a highly eccentric orbit that takes it both inside and outside the orbit of Phobos. This has allowed it to collect still images of the entire surface of Phobos, which (I assume) have been digitally mapped onto a 3D model of the moon and rendered into this movie.
Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
https://www.cloudbait.com

User avatar
Psnarf
Science Officer
Posts: 320
Joined: Fri Feb 26, 2010 6:19 pm

Re: APOD: Phobos 360 (2013 Dec 25)

Post by Psnarf » Wed Dec 25, 2013 3:52 pm

Looks more like a captured asteroid than a moon.

--
Throughout the New Year, may you and yours enjoy Health, Happiness, and Prosperity!

User avatar
Chris Peterson
Abominable Snowman
Posts: 18112
Joined: Wed Jan 31, 2007 11:13 pm
Location: Guffey, Colorado, USA
Contact:

Re: APOD: Phobos 360 (2013 Dec 25)

Post by Chris Peterson » Wed Dec 25, 2013 4:02 pm

Psnarf wrote:Looks more like a captured asteroid than a moon.
Not impossible, but captures are rare and dynamically difficult. I prefer the theory that it was ejected from the Martian surface after a large impact. What we need is a piece of it; it is unfortunate that the Russian sample return mission failed.
Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
https://www.cloudbait.com

User avatar
geckzilla
Ocular Digitator
Posts: 9180
Joined: Wed Sep 12, 2007 12:42 pm
Location: Modesto, CA
Contact:

Re: APOD: Phobos 360 (2013 Dec 25)

Post by geckzilla » Wed Dec 25, 2013 6:08 pm

Just call me "geck" because "zilla" is like a last name.

User avatar
Ann
4725 Å
Posts: 13372
Joined: Sat May 29, 2010 5:33 am

Re: APOD: Phobos 360 (2013 Dec 25)

Post by Ann » Wed Dec 25, 2013 7:33 pm

Phobos, Scratch and...
Click to play embedded YouTube video.
On a slightly more serious note, I, as a color commentator, find the dark color of Phobos interesting. What has caused it? The composition of this Martian moon? Or the exposure to very strong UV radiation from the Sun? Maybe a layer of dark dust, similar to what causes the strange coloring of Saturn's moon Iapetus?

Ann
Last edited by Ann on Wed Dec 25, 2013 7:44 pm, edited 1 time in total.
Color Commentator

User avatar
Chris Peterson
Abominable Snowman
Posts: 18112
Joined: Wed Jan 31, 2007 11:13 pm
Location: Guffey, Colorado, USA
Contact:

Re: APOD: Phobos 360 (2013 Dec 25)

Post by Chris Peterson » Wed Dec 25, 2013 7:44 pm

Ann wrote:On a slightly more serious note, I, as a color commentator, find the dark color of Phobos interesting. What has caused it? The composition of this Martian moon? Or its exposure to very strong UV radiation from the Sun?
It would be necessary to look at some of the work on the spectral characteristics of the Martian moons to understand this better, but airless bodies are subject to space weathering (of which UV exposure is just one component), and in general this results in a reduced albedo.
Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
https://www.cloudbait.com

ta152h0
Schooled
Posts: 1399
Joined: Mon Aug 29, 2005 12:46 am
Location: Auburn, Washington, USA

Re: APOD: Phobos 360 (2013 Dec 25)

Post by ta152h0 » Wed Dec 25, 2013 8:05 pm

That potato looks like it got into an epic fist fight with something
Wolf Kotenberg

User avatar
Beyond
500 Gigaderps
Posts: 6889
Joined: Tue Aug 04, 2009 11:09 am
Location: BEYONDER LAND

Re: APOD: Phobos 360 (2013 Dec 25)

Post by Beyond » Wed Dec 25, 2013 8:19 pm

Aw, the piggies in Ann's video don't move, here, or at youtube. Oh well, they make less mess that way. :lol2:
To find the Truth, you must go Beyond.

User avatar
Ann
4725 Å
Posts: 13372
Joined: Sat May 29, 2010 5:33 am

Re: APOD: Phobos 360 (2013 Dec 25)

Post by Ann » Wed Dec 25, 2013 8:48 pm

Beyond wrote:Aw, the piggies in Ann's video don't move, here, or at youtube. Oh well, they make less mess that way. :lol2:
No they don't!! :(

At least they grunt.

Let's try another grunt, and a very scratchy one at that, shall we?
Click to play embedded YouTube video.
Ann
Color Commentator

User avatar
Beyond
500 Gigaderps
Posts: 6889
Joined: Tue Aug 04, 2009 11:09 am
Location: BEYONDER LAND

Re: APOD: Phobos 360 (2013 Dec 25)

Post by Beyond » Wed Dec 25, 2013 9:53 pm

I think this one may be trying to be a dog. :lol2: It could also use a little combing between the ears. :yes:
To find the Truth, you must go Beyond.

navarch
Asternaut
Posts: 1
Joined: Wed Dec 25, 2013 10:53 pm

Re: APOD: Phobos 360 (2013 Dec 25)

Post by navarch » Wed Dec 25, 2013 10:58 pm

Perhaps the solar system's largest geode?

Night eyes

Re: APOD: Phobos 360 (2013 Dec 25)

Post by Night eyes » Wed Dec 25, 2013 11:21 pm

A geode, what a beauty idea, let's hope so.

Post Reply