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 virtualrotation 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.
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....
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.
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
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Chris L Peterson
Cloudbait Observatory https://www.cloudbait.com
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
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
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Chris L Peterson
Cloudbait Observatory https://www.cloudbait.com
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
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Chris L Peterson
Cloudbait Observatory https://www.cloudbait.com
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.
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
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Chris L Peterson
Cloudbait Observatory https://www.cloudbait.com
Phobos 360
