Mars Express Phobos Flyby March 3 2010

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MeteorWayne

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http://www.esa.int/esaSC/SEMDUGSJR4G_index_0.html

Auspicious orbit marks run-up to Phobos flyby


29 January 2010
On 26 January, Mars Express completed its 7777th orbit around the Red Planet, an auspicious milestone as the satellite is readied for the closest-ever flyby of Phobos, scheduled for just a few weeks from now.

....

Mars Express, on 3 March, to conduct the closest flyby and examination of Phobos, Mars’ largest moon. The flyby, at a planned altitude of just 50 km, will collect very precise radio Doppler data to help determine the moon’s gravity field more accurately than ever.

Mars Express imaged the martian moons Phobos and Deimos together on 5 November 2009
This close flyby will be bracketed by similarly close passages, which will be used for other scientific investigations including radar sounding and imaging.
Knowing the gravity field will help scientists to understand the distribution of mass inside the moon, which is another step in the quest to discover the origin of Phobos.

None of the other spacecraft now orbiting Mars can fly as close to Phobos. While Mars is the mission’s primary target, this flyby is an excellent opportunity for additional scientific investigation of the Mars system, and will boost overall science return
 
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3488

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Preliminary tracking of Mars Express from the Wednesday 3rd March 2010 closest pass are in.

Predicted deviation & actual are virtually identical, suggesting a homogenous interior. However a slighter greater deviation during approach suggests a more solid small 'Lump' on one side just under the surface of Phobos.

It will take approximately a week to properly examine this.

First images should also be avaliable soon from the Sunday 7th March 2010 pass.

First results from Mars Express tracking

Andrew Brown.
 
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EarthlingX

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3488":1uspq5tz said:
Preliminary tracking of Mars Express from the Wednesday 3rd March 2010 closest pass are in.

Predicted deviation & actual are virtually identical, suggesting a homogenous interior. However a slighter greater deviation during approach suggests a more solid small 'Lump' on one side just under the surface of Phobos.

It will take approximately a week to properly examine this.

First images should also be avaliable soon from the Sunday 7th March 2010 pass.

First results from Mars Express tracking

Andrew Brown.


A part with a higher density in the rubble pile or just an effect of Phobos rotation, which they probably calculated in ?
Where would such a higher density rock come from ? Impact ejecta would probably also be lower density, if coming from differentiated crust ?

What happens now to the theory that Phobos is hollow ? Could the part with lower density be the hypothesized cavern ? Denser part a sort of eccentricity ? Wait .. ? ;)

Wiki : Phobos (moon)

Wiki : Carbonaceous chondrite
Wiki : Chondrite

Wiki : C-type asteroid
Wiki : D-type asteroid

SDC Forum mission thread :
Mars Express Alive again with photos of both Martian Moons

( Post submit/success ratio = 17:7 )
 
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EarthlingX

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ESA Portal - Phobos flyby images : ( 3D image, video, .. )
15 March 2010
Images from the recent flyby of Phobos, on 7 March 2010, are released today. The images show Mars’ rocky moon in exquisite detail, with a resolution of just 4.4 metres per pixel. They show the proposed landing sites for the forthcoming Phobos-Grunt mission.

The High Resolution Stereo Camera (HRSC) onboard the ESA spacecraft Mars Express took this image of Phobos using the HRSC nadir channel on 7 March 2010, HRSC Orbit 7915. This image has additionally been enhanced photometrically for better bringing features in the less illuminated part. Resolution: about 4.4 meters per pixel.

Credits: ESA/DLR/FU Berlin (G. Neukum)

The High Resolution Stereo Camera (HRSC) onboard the ESA spacecraft Mars Express took this image of the Phobos Grunt landing area using the HRSC nadir channel on 7 March 2010, HRSC Orbit 7915. The image resolution is 4.4m per pixel and the insert marks the proposed landing region and sites for Phobos-Grunt.

Credits: ESA/DLR/FU Berlin (G. Neukum)
 
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3488

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Thanks EarthlingX. About time too that ESA have released something.

Sharpened crop of deep crater on Phobos. Note how material has slid down the walls.


Hills & craters on the limb of Phobos.


Proposed Phobos-Grunt landing area.


Andrew Brown.
 
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silylene

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Andrew, thank you!

The proposed Phobos-grunt landing area looks like it is the most boring area on Phobos! I was hoping for something better. I know they are trying to avoid landing on a boulder, but perhaps such caution is less warranted in the near-microgravity environment of thei little moon's surface.
 
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EarthlingX

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3488":3n7lne94 said:
Thanks EarthlingX. About time too that ESA have released something.

Sharpened crop of deep crater on Phobos. Note how material has slid down the walls.
http://i233.photobucket.com/albums/ee18 ... sExpre.jpg

Hills & craters on the limb of Phobos.
http://i233.photobucket.com/albums/ee18 ... rsExpr.jpg

Proposed Phobos-Grunt landing area.
http://i233.photobucket.com/albums/ee18 ... ndinga.jpg

Andrew Brown.
Similar layering as seen on Helene, and Phobos is Ares Synchronous (?), i think this is point for my assumption about layering on Helene being result of tidal effects.
If i'am correct, layering should be parallel to the planet surface, right ?
What else could be the cause ?

Good job with images :cool:
 
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3488

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Hi EarthlingX,

Yes both Phobos & Deimos are Aresynchronous (keeps the same face turned towards Mars all of the time).

The layering is interesting. It was seen on the Saturn moon Helene, which unlike Phobos is icy, & also seen on on main belt asteroid 243 Ida, which of course is orbiting the Sun, within the Asteroid Belt.

I suspect the layering is 'concentric' to the centre of the interior.

Below, three more of my efforts.

Crop of limb.


A 4 KM wide sample area including a small crater with a boulder in the centre.


A two KM & one KM wide sadowed craters near the evening terminator on Phobos.


silylene":3b4huzmb said:
Andrew, thank you!

The proposed Phobos-grunt landing area looks like it is the most boring area on Phobos! I was hoping for something better. I know they are trying to avoid landing on a boulder, but perhaps such caution is less warranted in the near-microgravity environment of thei little moon's surface.
Thanks silylene,

My guess is that is what the reasoning is. Russian luck with the Martian system has been pretty lacking, so I guess this is to maximize the chances of a successful landing & sample return. I am looking forward to the panoramas also, will be interesting to see how Phobos would look to a human standing on there. The first asteroidal type landscape.

Andrew Brown.
 
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3488

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A wider angle view of the anti Mars side of Phobos.



Grooves following the terrain of Phobos.


North is to the left, east is top. I have rotated this crop to make this look more like a landscape.


Andrew Brown.
 
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3488

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Phobos from Mars Express on the Wednesday 10th March 2010 pass.



North Pole on Phobos. Area shown is approx 4 KM wide.


Unusual view of Stickney Crater seen from the other side than usual.


Andrew Brown.
 
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3488

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Bumpy, hilly, cratered limb of Phobos. Mars Express. Wednesday 10th March 2010.


Limb of Phobos rotated to look like a horizon. This section is approx 5 KM wide. Mars Express. Wednesday 10th March 2010.


Cratered, rugged, striated limb of Phobos, Mars Express. Wednesday 10th March 2010.


Andrew Brown.
 
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EarthlingX

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Thank you, this images make life a bit easier and prettier :)

I will continue with my unsolicited musings on the theme of tidal-effects being a culprit for those streaks, and i invite better explanations, ( as if i would have to say that ).

For comparison, something more close, could be some starting point of search, at least from a first glance, it looks similar :

Wiki : Glacial striation
Glacial striations or glacial grooves are scratches or gouges cut into bedrock by process of glacial abrasion. Glacial striations usually occur as multiple straight, parallel grooves representing the movement of the sediment-loaded base of the glacier. Large amounts of coarse gravel and boulders carried along underneath the glacier provide the abrasive power to cut the grooves, and finer sediments also in the base of the moving glacier further scour and polish the bedrock.
I will abuse Andrew's fine images for my silly case :
3488":23rj9usr said:
Yes both Phobos & Deimos are Aresynchronous (keeps the same face turned towards Mars all of the time).

The layering is interesting. It was seen on the Saturn moon Helene, which unlike Phobos is icy, & also seen on on main belt asteroid 243 Ida, which of course is orbiting the Sun, within the Asteroid Belt.

I suspect the layering is 'concentric' to the centre of the interior.
3488":23rj9usr said:
A two KM & one KM wide sadowed craters near the evening terminator on Phobos.


Andrew Brown.
And of course, from this awesome set, just this :roll: :

3488":23rj9usr said:
Phobos from Mars Express on the Wednesday 10th March 2010 pass.
This doesn't look very concentric to me, more as if Phobos was hit by something, and changed it's facing to the planet.
That curving path also looks funny. Could something roll over it's surface ? Or was it an asteroid, crushed by tidal effects hitting Phobos in a stream ? Maybe picked up, by a rotation ? Something else ?

3488":23rj9usr said:
North Pole on Phobos. Area shown is approx 4 KM wide.
It is easy to set then, i guess. This grooves should be halving Phobos, pointing slice faces to the Mars. I don't expect layers to be distinct all the way to the other side and through the centre, though i don't think it impossible.

3488":23rj9usr said:
Unusual view of Stickney Crater seen from the other side than usual.

Andrew Brown.
Probably some crossing of crater walls, that would make it sharp, i guess.

If this is too much spamming with images, please say so.

edit2:fixed some quoting mess
edit3:and some grammar, duh ..
edit4:and i would like to emphasize, that the last image is :eek: :shock: awesome :cool: , of course, as are all the others :roll:
 
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yevaud

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3488":2m1j8re8 said:
Phobos from Mars Express on the Wednesday 10th March 2010 pass.



Andrew Brown.
That's one hell of an image, I must say. Crisp, clean, and with a great deal of surface detail.

The striation are curious. Where, precisely, did Phobos originate? I would suppose, given proximity, that Phobos was a capture of a Near Belt object that had been perturbed out of it's orbit via collision with another object - which was the cause of the striations via collision.

Just an assumption now, nothing solid.
 
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EarthlingX

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yevaud":1dgxfr4x said:
3488":1dgxfr4x said:
Phobos from Mars Express on the Wednesday 10th March 2010 pass.



Andrew Brown.
That's one hell of an image, I must say. Crisp, clean, and with a great deal of surface detail.

The striation are curious. Where, precisely, did Phobos originate? I would suppose, given proximity, that Phobos was a capture of a Near Belt object that had been perturbed out of it's orbit via collision with another object - which was the cause of the striations via collision.

Just an assumption now, nothing solid.
Plausible assumption. In such case, those striations would be caused by compressing forces of the hit, i suppose ? I know experiments have been done with impacts, was there something comparable, with striations as a result ? Layers would in such case be centred out from the place of the impact, similar to onion ?

For me to read, a couple of Wiki links :
- Tidal force
- Tidal locking
- Tidal acceleration

Nice image, indeed :cool:

I rotated it 90 deg to the right, to allow me more wild guessing :

Here i guess, that image was taken from closer to Mars than Phobos at this moment, i made some ugly markings, to show assumed direction of Mars surface.

I assume it is not oriented as a fill on the above image, just the first fill, that was closest to the idea.

I think that some 'Mars-shine' can also be seen on the lower right part of the above image, meaning Mars surface is quite lower down, and also gives the idea of Sun's position at the moment. If i remember correctly, Mars Express was coming down over N of Mars, while Phobos was orbiting around the equator, if that means anything.

I think, in this image, it looks like a drop of something, with a tail away from Mars.

Bulge can be seen beginning to form in the lower left half, i think.
 
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emperor_of_localgroup

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What do you guys say to the claim that Photos is an artificial satellite of Mars, not natural?
I heard even Carl Sagan and a Russian astronomer started this opinion.

Some claim the Phobos is hollow inside, shouldn't its gravity tell us if it is hollow or solid?
 
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silylene

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Phobos doesn't look very artificial to me!

It's density and matter distribution is being carefully measured. So far, it looks like a porous rubble pile.
 
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3488

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Hi emperor_of_localgroup,

Yes silylene is correct. Phobos indeed appears to be made of material held together by gravity. There are likely to be larger solid lumps contained within (Mars Express may have detectrd on such lump inbound on Wednesday 3rd March 2010).

There may be voids & caverns inside Phobos, but Phobos is certainly not hollow. Phobos's density of 1.89 G/CM3 is too high for the body to be hollow like a football, but far too low to be solid coherent rock.

Below is the 59 KM by 47 KM Main Belt Asteroid 253 Mathilde, a genuinely known type C asteroid a permanent member of the asteroid belt, with a density of only 1.3 G/CM3.

Spectrally 253 Mathilde & Phobos are very similar, densities are approx 0.6 G/CM within each other & 253 Mathilde has huge craters 30 KM wide (slightly larger than the whole of Phobos, which is 27 KM long) & 10 KM deep, (the deceptively flat top of 253 Mathilde is the rim of another 30 KM wide crater containing the north pole of the asteroid) that look as though material has been 'pushed in', suggesting that 253 Mathilde is also a porous rubble pile, made of similar materials to Phobos & Deimos.

Like Phobos, 253 Mathilde also appears to display a more solid 'lump' as detected by the NEAR Shoemaker spacecraft.


P.S: 253 Mathilde is the third slowest known rotating asteroid taking 17 days, 9 hours & 45' to rotate on it's axis.

Andrew Brown.
 
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EarthlingX

Guest
3488":2v1qk5e0 said:
Below is the 59 KM by 47 KM Main Belt Asteroid 253 Mathilde, a genuinely known type C asteroid a permanent member of the asteroid belt, with a density of only 1.3 G/CM3.

Spectrally 253 Mathilde & Phobos are very similar, densities are approx 0.6 G/CM within each other & 253 Mathilde has huge craters 30 KM wide (slightly larger than the whole of Phobos, which is 27 KM long) & 10 KM deep, (the deceptively flat top of 253 Mathilde is the rim of another 30 KM wide crater containing the north pole of the asteroid) that look as though material has been 'pushed in', suggesting that 253 Mathilde is also a porous rubble pile, made of similar materials to Phobos & Deimos.

Like Phobos, 253 Mathilde also appears to display a more solid 'lump' as detected by the NEAR Shoemaker spacecraft.


P.S: 253 Mathilde is the third slowest known rotating asteroid taking 17 days, 9 hours & 45' to rotate on it's axis.

Andrew Brown.
I would think, this is how an asteroid, hit by another would look like. There is also a hint about it's composition, since it was plastic enough to survive without cracking and reassembling. There is something that looks like striations on the right side, but more apart, than those on the Phobos, and also not distributed so evenly.
If this rock was hit by another, it would also probably slow down it's rotation.

Could something sliding over Phobos surface cause those streaks ? It would have to be a very low orbit, i guess ... :roll:
 
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3488

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This is the Anti Mars side of Phobos, obtained by Mars Express on: Wednesday 10th March 2010.

Because Mars Express was so close to Phobos, Mars below Phobos was completely eclipsed!!!!!!


Link to Full Sized Image.

Andrew Brown.
 
K

kg

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When estimating the density of Phobos how do they first figure out the volume of such a irregularly shaped object with such HUGE craters?
 
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3488

Guest
Hi kg,

Great Question!!! :)

IIRC there is a computer program called SPUDS (as in spuds, potatoes).

What happens is that images are draped over a vitual sphere with a gridline & the sphere is then deformed to match the 3D images or if the lighting is precicely known, normal 2D images. Then the volume can be worked out. It's a laborious task. Once volume has been worked out, then density of said body can be worked out by the tracking of the craft passing by or orbiting.

Other clues can be size of impact ejecta verses crater sizes, etc.

It has also been used for asteroids 951 Gaspra, 243 Ida, 253 Mathilde & 433 Eros, asteroids seen at high resolution from more than one angle. It will certainly be used for 1 Ceres, 4 Vesta & 21 Lutetia, when these are seen at high resolution.

Andrew Brown.
 
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