Phobos Options

[Guest_Sunspot_*]

http://www.esa.int/SPECIALS/Mars_Express/

These images, taken by the High Resolution Stereo Camera (HRSC) on board ESA’s Mars Express spacecraft, are Europe’s highest-resolution pictures so far of the Martian moon Phobos.

http://www.esa.int/SPECIALS/Mars_Express/SEM21TVJD1E_0.html

[Phil Stooke]

Here's a Mars Express Phobos image from orbit 1607- a distant view. There is a close view on this orbit, but I haven't got the patience to download 600 Mb of mostly dark sky.

Phil

[djellison]

What is it with the PDS/PSA and their total hatred of Zip/Rar/GZ'ing files that actuall comrpess REALLY well...

At least the small bodies node have the right attitude for this stuff.

Doug

[Guest_PhilCo126_*]

Waaw thanks for sharing those!

[Phil Stooke]

Mea culpa - I see now that the second image from that orbit, the 600 MB file, is of Mars, not Phobos.

Phil

[tedstryk]

600 MB? The biggest Phobos images from that orbit are about 2 MB. Where were you looking? I was on the PDS Geosciences node.

Here are the two highest resolution images from this orbi (1607).

[Phil Stooke]

I checked this after reading your question, Ted. The Data directory has the full res images, and for the largest image from that orbit it says:

Wednesday, April 26, 2006 6:49 AM 697587740 h1607_0009_nd2.img

697 Mb. But I was mistaken in thinking it was Phobos, I assumed that without checking - the second set of images from 1607 are of Mars. Even so, the largest Phobos image on that orbit, the nd2 image, is 9548940 bytes. Your images are the "super-resolution" images which are a lot smaller.

There are some very similar images of Phobos in orbit 1574 as well.

Phil

[Phil Stooke]

- and another in orbit 1558, but this one is from orbit 1212, the nadir (nd2) image:



Phil

[Phil Stooke]

I'm still exploring the Mars Express Phobos images. This, I think, is the highest resolution image yet, from orbit 756. The original file was 169 MB, but largely dark sky. I have played with the contrast a bit to brighten the terminator. Several blocks casting shadows can be found along the terminator.

Phil

[ugordan]

Nice image, Phil. Where do the JPEG-ish artifacts come from, was this one lossy compressed before transmission?

[Phil Stooke]

No, I compressed it severely to reduce the file size for posting on UMSF.

Phil

[dilo]

Very impressive shot, Phil... resolution should be around 3m/pixel!
The file you posted is only 460k, I think is worth to re-post a less compressed version... please!

[dilo]

sorry, wrong re-post.

[Phil Stooke]

I will put the uncompressed image on an external website tomorrow.

Phil

[tedstryk]

I will put the uncompressed image on an external website tomorrow.

Phil

The best I could do with 16 bit lossless compression was over 9 MB!

[Phil Stooke]

Good point, Ted - actually I'll be reducing it to 8 bit after a judicious contrast stretch (actually 2 different contrast stretches merged), and then saving it as a high quality jpg, so it will be compressed, but a lot less than my post.

Phil

[Phil Stooke]

Here's another one... orbit 748.

Phil

[elakdawalla]

Oh, that's a nice one, Phil!

Are you methodically posting every halfway decent Phobos image here or are you just making selections of your favorites?

--Emily

[Phil Stooke]

I'm not being methodical, I'm just playing. I needed a break from more serious stuff. But I'll probably end up posting any decent Mars Express pics as I find them.

Phil

[Ian R]

Good grief! Is it my imagination, or are there really two sets of grooves in the image that Phil just posted, intersecting at right angles?

How does this tally with the theory that the grooves were produced by interactions between Phobos and debris in orbit around Mars?

Ian.

[edstrick]

Despite impeccible logic and analysis "proving" how the grooves were formed by impacting debris, I just don't believe it. Yah... one group from 10:00 clock to 4:00 clock and a second finer set from 1:00 clock to 7:00 clock angle. _AND_, roughly bisecting them at an angle of 5:30 to 11:30 clock angle is a non-groove linear splatter pattern that looks like it *IS* splatter-cratering from a jet of debris.

[Ian R]

Good catch on the splatter pattern Ed. That certainly does look more like a crater chain from a debris or cometary impact.

[Phil Stooke]

Here's a link to the higher quality Phobos image posted above. It's reduced from 16 to 8 bit, cropped and saved as a high quality JPG, so it is compressed but not too badly. The 16 to 8 conversion was done twice, once to favour dark areas, and the results merged using my secret sauce recipe. I'll keep this up here for a few weeks and then remove it so get it while it's hot.

Phil

http://instruct.uwo.ca/geog/136a/hrsc756_phobos.jpg

[elakdawalla]

I've mirrored it here...
http://s3.amazonaws.com/planetary/10212/hrsc756_phobos.jpg

--Emily

[volcanopele]

Phil, do you know the pixel scale on that particular image from orbit 756?

[Phil Stooke]

The PDS label says 5.9 m/pixel. and roughly 5000 pixels across 30 km seems to support that value.

Phil

[dilo]

Thanks for the great image Phil, I hope one day you will reveal your secret sauce recipe...
(I was wrong about image scale because I estimated it using Phobos mean radius instead of diameter)

[Phil Stooke]

Here's a nice new Phobos image from Mars Express, orbit 3909:




Phil

[scalbers]

Out of curiosity, how are things going with mapping of Phobos? The best global map I've seen is the USGS airbrushed version. FWIW, my mapping software is approaching the point where I can consider utilizing more general shape models, vs a simpler triaxial ellipsoid.

[Phil Stooke]

I should have added to my previous post - it came from one of the abstracts at the ESA Mars Conference - see thread under Conferences. Willner et al., in the Friday Workshops.

Mapping - there has been no serious work since Viking. I've been saying for years that I'll make a new global mosaic with the best images, but other things have prevented me. But I will certainly do so when Phobos-Grunt flies, or if CSA's PRIME gets funded. The abstract above refers to a new global shape model, which will help improve the next round of mapping.

Phil

[tty]

Good catch on the splatter pattern Ed. That certainly does look more like a crater chain from a debris or cometary impact.

Now that is interesting. How do you get a splatter pattern/crater chain on a body with essentially zero gravity? It certainly can't be by stuff just falling back to the surface. Anything moving slowly enough to fall back on Phobos probably wouldn't be able to crater a marshmallow.
I suppose a string of debris might stay together well enough to hit Phobos on a subsequent orbit but it seems rather unlikely. It seems at least as likely to be debris coming from an impact on Mars itself.

[elakdawalla]

Wow, Phil, that's a really cool image, thanks for pointing it out!

--Emily

[Stu]

... and add a bit of colour, just 'cos it's Sunday night and there's nothing on telly until Medium comes on...

[nprev]

Great stuff, Phil & Stu!!! Now I know exactly how Phobos must have appeared to the crew of the spacecraft Rolling Stone as it approached Phobos in Heinlein's immortal novel...absent the industrial complexes and filled landing berths, of course...

Quick inspiration:

we sense therefore we are

unmanned and alone
solitary robots peer deeply into the Unknown
seeing, tasting, hearing that which no human has yet known,
like a splash of water or blast of radiation
on tender skins

We, safe in the cradle, see vistas dreamed of
yearned for, in our infant dreams
by generations denied their future by tumult,
by the restless and capricious nature of our species
by priorities, set too often by
those who cannot see far horizons,
even through eyes of silicon, gallium arsinide, feed horns and reflectors...

blindness is inexcusable
as the spectrum of the Universe unveils itself, reluctantly,
as bigger than our minds
what challenge, what wonder, can possibly compare?

we must see, at least

in order that someday we may touch

[Pygmee]

Here's a nice new Phobos image from Mars Express, orbit 3909:




Phil

Hey Phil, could you tell me where you got the pictures from orbit 3909, because I do find only the raw images until the orbit 3160 on the ESA server...
Thanks a lot

[Phil Stooke]

I found it in the place mentioned in post 30, above.

Phil

[elakdawalla]

Here's the direct link to the Willner et al. abstract (PDF).

--Emily

[scalbers]

Shall be interesting to see what shape model results Willner et al. are going to present at the November conference.

Seeing that image I wonder who launched that potato into low Mars orbit anyway ?

[elakdawalla]

Dr. Willner said I'd need to ask Neukum directly for permission to post that other image, but he pointed out one that had been released on the Web in February (apologies if someone else already posted this elsewhere):

Phobos über der Marsatmosphäre

--Emily

[Stu]

Wow, that's a gorgeous picture of Phobos, thanks for the link Emily... that one passed me by, somehow...

[ugordan]

That picture was around for quite a while now: http://www.unmannedspaceflight.com/index.p...ost&p=84812

[Phil Stooke]

Here are a couple of Mars Express HRSC images of Phobos, from the PDS courtesy of G. Neukum. They have had a bit of extra processing in my usual manner to brighten the terminator area.

Phil

[scalbers]

That's something with three different orientations of grooves I can see in the top image...

[t_oner]

It is already gridded, it will be easy for Phil to make us a new model and map.

[ilbasso]

At first glance, I thought we were looking at it through a screen door.

[Decepticon]

[peter59]

The High Resolution Stereo Camera (HRSC) on Mars Express is not the best instrument.

Orbit 3802, Phobos, image h3802_0003_sr2


Orbit 3802, Phobos, image h3802_0004_sr2

[djellison]

HRSC itself is great, but the super resolution bolt-on camera from which those two frames came from has never achieved good focus.

Doug

[peter59]

Mars Express (MEX) release #2.
February 14, 2008

Online Data Volumes - Mars Express

Orbit 3310, Phobos, image h3310_0000_s22


Orbit 3310, Phobos, image h3310_0000_s12

[peter59]

Another high (??) resolution image.

Orbit 3769, Phobos, image h3769_0004_sr2

[djellison]

Another high (??) resulution image.

Orbit 3769, Phobos, image h3769_0004_sr2

The SR2 dictates it's from the super resolution camera, bolted on to HRSC, and thus suffers the same issue I mentioned previously.

Doug

[algorimancer]

...has never achieved good focus.

I tried running Helicon Focus software on a few images. Looks like a combination of motion smear + out of focus, but the dominant effect seems to be motion smear. Due to the jpeg artifacts it's a little difficult to do a good job of this, but here are some images with the motion smear (somewhat) corrected. I think that if I had uncompressed versions of the images then I could pull quite a bit of fine detail from them.

[ugordan]

I don't think it's motion smear, more like noncircular PSF due to out of focus deformity in some part of the optics. It gives an appearance of vertical motion smear. It would probably be possible to do a proper deconvolution if we knew the PSF exactly (say by imaging a star), but as I recall the amount of defocus isn't constant either.

[Phil Stooke]

It certainly is not motion smear, but it does look like it because there is a 'double exposure' effect. Regardless, they are still nice images in other respects, and are being used to improve the shape model of Phobos (The other HRSC images are less useful for that because they are from a scanning rather than framing camera). The top one just above is inside Stickney. These pics come in sets of 4 or 5 making up strips across the surface, and would make nice mosaics.


Phil

[mgrodzki]

[peter59]

It certainly is not motion smear, but it does look like it because there is a 'double exposure' effect.

'Double exposure' effect.
Orbit 3196, Deimos, image h3196_0005_sr2.

[peter59]

These pics come in sets of 4 or 5 making up strips across the surface, and would make nice mosaics.

Orbit 3802 - images h3802_0003_sr2, h3802_0005_sr2, h3802_0005_sr2


Orbit 3802 - image h3802_0000_s12

[algorimancer]

I don't think it's motion smear, more like noncircular PSF...

I'll take your word on that. Incidentally, what is "PSF"?

[djellison]

the S12 image is pushbroom.

PSF = Point Spread Function. i.e. the contribution of surrounding pixels to the pixel in question. With accurate info on that, you can subtract it all back out again..ish...roughly.

Doug

[tedstryk]

Here is a quick attempt. There does seem to be motion blurring in some of the data, almost as if it is a double exposure with one of the two slightly smeared in a direction almost but not quite perpendicular to the direction of the double exposure offset.



Edit: The bit of motion blur I mentioned could also be explained by optics being slightly out of alignment. Normally, the difference between the two is obvious, but this is too slight for that.

[mgrodzki]

i am wondering the nature of these phobos and deimos releases… are these just additional images they captured last year but we just hadn’t seen them until they released the full sets of data?

[tedstryk]

They were, for the most part, not in official releases, but were in the raw data release. Much of this has been available via ESA's PSA for a long time.

[mgrodzki]

They were, for the most part, not in official releases, but were in the raw data release. Much of this has been available via ESA's PSA for a long time.

oh, the sudden activity in this thread lead me to believe this was a new batch of materials.

are the full “global” views posted here composites that some of you have stitched or are they just full views snapped by MExpress?

[GravityWaves]

Mars Express to rendezvous with Martian moon
http://www.esa.int/SPECIALS/Mars_Express/SEMVGAWIPIF_0.html
16 July 2008
Scientists and engineers are preparing ESA’s Mars Express for a pair of close fly-bys of the Martian moon Phobos. Passing within 100 km of the surface, Mars Express will conduct some of the most detailed investigations of the moon to date.

The series of fly-bys will take place between 12 July and 3 August. During the second encounter, the spacecraft will fly within 273 km of the surface. Six days later, Mars Express will close to within just 97 km.

Although the Red Planet itself has been studied in detail, very little is known about the origins of its moons, Phobos and Deimos. It is unclear if the moons are actually asteroids that were captured by Mars’s gravity and never left its orbit. Another possibility is that Phobos and Deimos are actually surviving planetesimals, bodies which formed the planets of the Solar System. They may also be remnants of an impact of a large object on Mars.

As Mars Express closes-in on Phobos, the data gathered will help scientists answer these questions.

[Phil Stooke]

"As it flies by at a distance of 97 km, Mars Express will image areas of Phobos that have never been glimpsed before. "

... by Mars Express. The whole surface of Phobos was imaged by Viking.

Oh for a Deimos encounter.... there's a world we really do need new images of.


Phil

[tedstryk]

Yes, particularly the trailing hemisphere.

[dvandorn]

"As it flies by at a distance of 97 km, Mars Express will image areas of Phobos that have never been glimpsed before. "

... by Mars Express. The whole surface of Phobos was imaged by Viking.

And some people got offended when I mentioned the ESA tendency towards "little lies"?

If it ain't exactly the truth... *sigh*...

-the other Doug

[Hungry4info]

Does anyone know when those images from the 97 km flyby will be made available?

[nprev]

Uh.... <Ahem!> Well, um...that's a pretty good question, and all I'm gonna say.

[elakdawalla]

Agustin Chicarro (project scientist) told me they were supposed to be downlinked Friday, and that there should be some images released on Monday.

--Emily

[Stu]

00.12... bye bye Monday...

Maybe tomorrow...

[tedstryk]

He said Monday, but he didn't say which Monday

[Hungry4info]

He said Monday, but he didn't say which Monday

AAAhhh! Ha ha! They tricked us! =P ...

[nprev]

Hungry, just so you know (if you don't already), releases from ESA can be a bit erratic for a whole lot of known and unknown reasons that I definitely don't want to get into for reasons of forum decorum and that have been extensively discussed previously. Gotta wait & hope, is all.

[Hungry4info]

Hungry, just so you know (if you don't already), releases from ESA can be a bit erratic for a whole lot of reasons that I definitely don't want to get into for reasons of forum decorum and have been extensively discussed previously. Gotta wait & hope, is all.

Oh yes, I'm certainly aware. ESA's public relations has always been a source of agitation for me.

I think I've heard perhaps two or three bits of news from Venus Express in it's whole mission. I've seen perhaps two pictures from the mission.

[nprev]

Oh yes, I'm certainly aware. ESA's public relations has always been a source of agitation for me.

You'll find lots of company here, then...

[Stu]

Just heard back from the ESA Media office...

"We are still waiting for the material, but expecting to receive the first images by the end of the day or tomorrow.

We will publish them on the web (link below) as soon as possible (tomorrow or Thursday the latest).

http://www.esa.int/esaSC/index.html"

[3488]

unnecessary quoting removed

Thanks Stu,

I was beginning to wonder also. Does anyone know what the resolution of the images at closest approach will be, 1 metre per pixel, better, worse? Hopefully we'll get some more insight as to where Phobos camefrom.

Captured type D asteroid?

Formed around Mars?

Formed from impact ejecta from Mars?

My bet is still option 1, despite the difficulties with explaining orbital mechanics, but I still think, Phobos is as alien to Mars as the spacecraft we have sent.

It will be interesting to compare the new Phobos imagery with the NEAR / Shoemaker spacecraft imagery of similar resolution of asteroid 433 Eros.

Perhaps Mars Express could do similar with Deimos? Comparisons with the MARSIS & multispectral imagers / spectrometers of the two would be most fascinating.

Andrew Brown.

[CAP-Team]

Using spice kernels (for the spacecraft, Mars and Phobos) I tried to simulate the Mars Express Phobos flybies.
Underneath the images of how Phobos would approximately look like at closest approach.
The field of view in these images is 30 degrees (I don't know what field of view Mars Express has).

17 july 2008 (273 km)


23 july 2008 (97 km)


28 july 2008 (361)


I wonder how accurate Celestia will be

[djellison]

width of the HRSC swath is about 12 degrees - covering 5000ish pixels.

Doug

[bear10829]

A photo of Phobos quoted to have been made during the 93 km flyby last week was published
in the Nature & Science section of todays Frankfurter Allgemeine Zeitung, a major German newspaper.
G. Paul, who is frequently writing about space topics there, gave some general information about
the moon and a hint, that the photos cover the proposed Phobos-Grunt landing site.
This might be an indication that some release of data is near.

Best,
Oliver

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[nprev]

If I read that correctly, the headline says "Over Mars: A Cosmic Potato Named Phobos"? Hilarious!!!

[Dominik]

Yes, the translation of the title is correct .

[lyford]

So can we nickname Phobos-Grunt "SPUDnik?" *ducks*

[3488]

Link to DLR site of the Phobos Grunt landing site.

Images appearing now.

Andrew Brown.

[volcanopele]

Here is the link to the press release:

http://www.dlr.de/en/DesktopDefault.aspx/t.../86_read-13161/

[Hungry4info]

Here is the link to the press release:

http://www.dlr.de/en/DesktopDefault.aspx/t.../86_read-13161/

The image they provided there looks pretty distorted (The 3.74 Mb image). Do they intend to clean that up?

[elakdawalla]

I don't know about distortion -- Phobos looks pretty distorted in general; I can tell you from experience that it can be really hard to tell whether you have an oblique perspective or if an image has been unequally stretched. But I have a different question. There are two image releases that lack annotations. I thought that maybe they were the two views that had been combined to create the stereo image. But it appears that they are in fact the same image, stretched differently, and it seems that there was a gap in the image, some kind of data dropout, that was handled differently between the two images. In one the gap was closed, making an obvious seam; in the other, the gap was filled by duplicating pixels. I think that's what's going on anyway -- do others agree? The two pictures are
http://esamultimedia.esa.int/images/marsex...os-Flyby_H1.jpg
and
http://esamultimedia.esa.int/images/marsex...os-Flyby_H1.jpg
Odd.

--Emily

[elakdawalla]

The opposite of a usual activity: take apart an anaglyph to get its separate frames and voila, two more HRSC images of Phobos. Here's the red channel:

And the blue channel:

Enjoy!

--Emily

[ilbasso]

Interesting, the relatively small number of the tiniest craters. The dust layer must be mighty thick.
Really cool anaglyph on the home page - it really leaps off the screen at you!

[hendric]

I just had a really dumb idea, looking at that moon again. I was noticing how much it resembled the rocks around Opportunity at Victoria, and I started thinking...Hmm, what if those grooves were caused by differential micrometeoroid weathering due to layers? They do resemble at a macro scale the aeolian cross bedding we've seen before. That would add weight to the "Phobos is a chunk of Mars" idea!

[jasedm]

The best (for me) explanation I've heard for the grooves so far was highlighted by Emily over at TPS as being the result of Phobos sweeping up ejecta in chains from Martian impacts. Scroll down on the linked article to see a computer simulation which is a good match to the observed grooves.
But looking at the latest pictures, they seem to be far too straight and of regular width to be secondary crater chains - looking much more like collapse features to my untrained eye.
The mystery remains....

[Paolo]

In Astronomy & Astrophysics: New astrometric observations of Phobos with the SRC on Mars Express

[Harkeppler]

Mayby grooves on phobos seem not to be due to secondary impacts from asteroid impacts on Mars; they are too defined and regularly for that. These computer simulations seems to give only the trajectory of the ejected masses but the the width of the shower. And there are too much of these grooves and they are too regularly placed. This counts for some effects connected with material resistance against stress forces per length unit.

Especially, one set of grooves seems to be more or less concentric or better: coaxial along the Mars-anti-Mars-axis and can be explaned easily with tidal effects. The "craters" along the grooves may be simply sinkholes, especially because there are no ejecta. The other set of grooves (here highlighted in red) is nearly perpendicular to the other one and can be formed earlier by the same way; a large impact may have altered phobos orientation by chance and after that tidal fractures occure in a new set. So, that older bunch of grooves is orientated around the old Mars-anti-Mars axis of Phobos. Here:

http://www.planetary.org/blog/article/00001391/

or here

http://www.lpi.usra.edu/meetings/lpsc2006/pdf/2195.pdf

You can see the both sets, but you need another cartographic projection to see the old set as a concentric/coaxial one as well as the other.

Both groove sets are not (the old one) or not well (the new one) converging to two points but slicing phobos more like a cut potato. Here, the non-sperical shape of phobos and cartographic problems with this fact should be considered; the pseudo-convergence is an articfact of the cylindrical projection!

I would also consider that Phobos had been in an elliptic orbit first, so diffential stresses du to the tidal force change between apoareum and periareum and libration (nodding) effects due to the constant rotation period and the inconstant orbital angular velocity would have forced a result. A large impact, mayby the Stickney forming impact, would have altered the meanwhile circular orbit to an elliptic one again and it altered Phobos spin and orientation. So a second set of grooves came to existence.

You may recognize that the younger grooves, which are mostly sharper defined and smoother than the older ones (red) cross through them (and not opposite) which will give a hint which groove set was the former one.

The Stickney-impact itsself may be "buffered" by the weak material itsself, like the craters on asteroid Mathilda, and does not harm the whole structure. It is like shooting a projectile in styrofam...

It would be interesting to look for some grooves on several other moons like Amalthea; in the Saturnian system so much dust maybe hide features like that on the innermost moons.

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[SteveM]

In Astronomy & Astrophysics: New astrometric observations of Phobos with the SRC on Mars Express

The "new obervations" reported don't include the recent batch of observations discussed here. The most recent observation in the article is dated 2007-02-25T02:44:11.994

The main concern is with the fine details of Phobos' orbit.

Steve M

[charborob]

Interesting article about Phobos on the ESA website, based on the recent flyby:

ESA closes in on the origin of Mars’ larger moon

[tanjent]

In the article just quoted by charborob, there is an animation of Mars Express being diverted from its orbit during a close pass by Phobos. The interesting thing about this simulation is the way MEX returns to its original orbit after the deviation. It looks kind of like the maker of the simulation has added the symmetric plot of a normal distribution to the original unperturbed track of the spacecraft. Is this really how it would happen, or would the spacecraft experience a permanent change in its orbit due to the small gravity assist derived from Phobos? Observatoire Royal de Belgique must know a lot more than most of us about orbital mechanics, but maybe in this case they are pulling our legs and expecting us not to notice?

[peter59]

I checked "forgotten" Mars Express archive and I stated that this year Phobos has been photographed several times. Unfortunately, the quality is not stunning.



and Phobos over Mars craters.

[Phil Stooke]

I like the last two transit images! More close passes would certainly be nice, especially if they showed the Phobos-Grunt landing region better.

Phil

[charborob]

Transit image modified to show the Martian surface better.

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