#phobos — Public Fediverse posts
Live and recent posts from across the Fediverse tagged #phobos, aggregated by home.social.
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This paper describes the colour dichotomy on Phobos:
Murchie et al., 1999. Mars Pathfinder spectral measurements of Phobos and Deimos: Comparison with previous data. JGR Planets, v. 104(E4), pp.9069-9079. https://agupubs.onlinelibrary.wiley.com/doi/pdfdirect/10.1029/98JE02248
This map is from that paper. The boundary between red and blue materials is diffuse and irregular but is sketched on with a curving dashed line. Is the blue Stickney ejecta?
#maps #mars #phobos #deimos -
This paper describes the colour dichotomy on Phobos:
Murchie et al., 1999. Mars Pathfinder spectral measurements of Phobos and Deimos: Comparison with previous data. JGR Planets, v. 104(E4), pp.9069-9079. https://agupubs.onlinelibrary.wiley.com/doi/pdfdirect/10.1029/98JE02248
This map is from that paper. The boundary between red and blue materials is diffuse and irregular but is sketched on with a curving dashed line. Is the blue Stickney ejecta?
#maps #mars #phobos #deimos -
Back in the saddle... It would be easy to assume from what we have seen of Phobos 2 that no very useful results were obtained from it, but this is not correct. Its images (visible and infrared) revealed something unexpected: the two sides of Phobos, leading and trailing in its orbit, have different colours, roughly a bit more blue on the leading side and a bit more red on the trailing side. The blue might be associated with the big crater Stickney.
#mars #phobos #deimos -
Back in the saddle... It would be easy to assume from what we have seen of Phobos 2 that no very useful results were obtained from it, but this is not correct. Its images (visible and infrared) revealed something unexpected: the two sides of Phobos, leading and trailing in its orbit, have different colours, roughly a bit more blue on the leading side and a bit more red on the trailing side. The blue might be associated with the big crater Stickney.
#mars #phobos #deimos -
Neither lander would have been able to see Mars in the sky (a favourite subject for space artists). Most landing plans target the region opposite Mars. That way the lander is hidden behind Mars while it is facing away from Earth, minimizing communication loss. Land facing Mars and the two comm loss periods are separate.
#mars #phobos #deimosPSA: I will be on the road for a few days. Normal service will resume as soon as possible.
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Neither lander would have been able to see Mars in the sky (a favourite subject for space artists). Most landing plans target the region opposite Mars. That way the lander is hidden behind Mars while it is facing away from Earth, minimizing communication loss. Land facing Mars and the two comm loss periods are separate.
#mars #phobos #deimosPSA: I will be on the road for a few days. Normal service will resume as soon as possible.
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The Phobos 2 images can be made into a photomap to show coverage. This version (top) also shows two instrument footprints (both were infrared detectors). The lower image shows the lander targets from this paper:
Sagdeev, R.Z. and Zakharov, A.V., 1989. Brief history of the Phobos mission. Nature, 341(6243), pp.581-585. https://doi.org/10.1038/341581a0
A small hopper would move around on the surface, another lander would last longer.
#maps #mars #phobos #deimos -
The Phobos 2 images can be made into a photomap to show coverage. This version (top) also shows two instrument footprints (both were infrared detectors). The lower image shows the lander targets from this paper:
Sagdeev, R.Z. and Zakharov, A.V., 1989. Brief history of the Phobos mission. Nature, 341(6243), pp.581-585. https://doi.org/10.1038/341581a0
A small hopper would move around on the surface, another lander would last longer.
#maps #mars #phobos #deimos -
...which we got about 2 weeks after publication. But pictures were slow to arrive (a bit like the current Tianwen-2 asteroid mission). Phobos 2 made several passes by Phobos, each closer than the last, but it failed before the landing phase of the mission. We got some images and other data including IR spectroscopy. Here are 3 images. Mars-shine is seen (exaggerated) on one image. We are seeing the end facing away from Mars, 180 longitude.
#mars #phobos #deimos -
...which we got about 2 weeks after publication. But pictures were slow to arrive (a bit like the current Tianwen-2 asteroid mission). Phobos 2 made several passes by Phobos, each closer than the last, but it failed before the landing phase of the mission. We got some images and other data including IR spectroscopy. Here are 3 images. Mars-shine is seen (exaggerated) on one image. We are seeing the end facing away from Mars, 180 longitude.
#mars #phobos #deimos -
After Viking came the Soviet Union's Phobos mission, in fact the last Soviet planetary mission before the Union broke up. There were 2 spacecraft, launched in summer 1988. Phobos 1 failed during flight but Phobos 2 arrived at Mars early in 1989. This was in my first year at Western and we got our news from early internet message boards (pre-WWW) or from newspapers and magazines. I would check our library nearly every day for new issues of Pravda and Izvestia...
#mars #phobos #deimos -
After Viking came the Soviet Union's Phobos mission, in fact the last Soviet planetary mission before the Union broke up. There were 2 spacecraft, launched in summer 1988. Phobos 1 failed during flight but Phobos 2 arrived at Mars early in 1989. This was in my first year at Western and we got our news from early internet message boards (pre-WWW) or from newspapers and magazines. I would check our library nearly every day for new issues of Pravda and Izvestia...
#mars #phobos #deimos -
And here is a global mosaic mostly made of Viking images - plus the north polar Mariner 9 image shown earlier. It is the fuzzy bit at top centre. Two students who helped with the project are named on the map.
So... Viking showed us most of the surfaces of Phobos and Deimos at good enough resolution to start planning missions to explore them. Who is first up?
#maps #mars #phobos #deimos -
And here is a global mosaic mostly made of Viking images - plus the north polar Mariner 9 image shown earlier. It is the fuzzy bit at top centre. Two students who helped with the project are named on the map.
So... Viking showed us most of the surfaces of Phobos and Deimos at good enough resolution to start planning missions to explore them. Who is first up?
#maps #mars #phobos #deimos -
Oh yes... before the mosaic, here is a mosaic of 3 frames taken at very low altitude of the upper part of the previous image. The subdued nature of the surface continues even down to this scale. Now we can see quite a few rocks. These are by far the highest resolution images ever taken of Deimos - even after almost 50 years they have not been bettered because no other spacecraft has ever passed this close to the little moon.
#mars #phobos #deimos -
Oh yes... before the mosaic, here is a mosaic of 3 frames taken at very low altitude of the upper part of the previous image. The subdued nature of the surface continues even down to this scale. Now we can see quite a few rocks. These are by far the highest resolution images ever taken of Deimos - even after almost 50 years they have not been bettered because no other spacecraft has ever passed this close to the little moon.
#mars #phobos #deimos -
Here is the best global view of Deimos from Viking. There are craters, but most are very subdued. Bright streaks seem to run downslope off a ridge at the bottom (which is near the equator) and down a crater wall. Tiny dark spots turn out to be clusters of boulders - the dark is really unresolved shadows of rocks. Peter Thomas made a map of Deimos as well, but we will move on to a photomosaic of it next.
#mars #phobos #deimos -
Here is the best global view of Deimos from Viking. There are craters, but most are very subdued. Bright streaks seem to run downslope off a ridge at the bottom (which is near the equator) and down a crater wall. Tiny dark spots turn out to be clusters of boulders - the dark is really unresolved shadows of rocks. Peter Thomas made a map of Deimos as well, but we will move on to a photomosaic of it next.
#mars #phobos #deimos -
There is a faint streak running vertically down the middle of the image - an artifact caused by spacecraft electronics. It's not a groove! There are none on Deimos. The lack of stereo in this large region made the Deimos shape model less reliable than we would have liked, and therefore the volume and density. The UAE orbiter Hope provided images to improve the shape a few years ago. We do have much better Viking images than this of Deimos... tomorrow!
#mars #phobos #deimos -
There is a faint streak running vertically down the middle of the image - an artifact caused by spacecraft electronics. It's not a groove! There are none on Deimos. The lack of stereo in this large region made the Deimos shape model less reliable than we would have liked, and therefore the volume and density. The UAE orbiter Hope provided images to improve the shape a few years ago. We do have much better Viking images than this of Deimos... tomorrow!
#mars #phobos #deimos -
Let's have a look at the full Viking image of Deimos from yesterday's post. Here it is. It was one of a pair, presumably for stereo, but the second was badly overexposed - only the terminator strip was visible - so stereo was not possible. Too bad because for many years this was the only image of about 30% of the surface of Deimos. See the bright spot on the limb at the 11 o'clock position -it's the crater seen in the last Mariner 9 image.
#mars #phobos #deimos -
Let's have a look at the full Viking image of Deimos from yesterday's post. Here it is. It was one of a pair, presumably for stereo, but the second was badly overexposed - only the terminator strip was visible - so stereo was not possible. Too bad because for many years this was the only image of about 30% of the surface of Deimos. See the bright spot on the limb at the 11 o'clock position -it's the crater seen in the last Mariner 9 image.
#mars #phobos #deimos -
Deimos has craters... but not many. The very small crater in the lower right part of this image of Deimos shows that the resolutions of the two images are not very different. What happened to Deimos? You can't inoculate against impacts, they must have occurred, but something erases them. Most likely it is seismic shaking when impacts do occur, maybe acting on an unusually thick surface debris layer. We need to see more to get to grips with this moon.
#mars #phobos #deimos -
Deimos has craters... but not many. The very small crater in the lower right part of this image of Deimos shows that the resolutions of the two images are not very different. What happened to Deimos? You can't inoculate against impacts, they must have occurred, but something erases them. Most likely it is seismic shaking when impacts do occur, maybe acting on an unusually thick surface debris layer. We need to see more to get to grips with this moon.
#mars #phobos #deimos -
A tale of two terminators. The terminator is the line between sunlit and unlit sides of a body. The one at left in this image is the kind of terminator we might expect on an asteroid... covered with craters. We have seen quite a few very small rubble-pile asteroids recently (Bennu, Ryugu, Itokawa) but larger bodies... we expect hem to have craters. This one is Lutetia imaged by ESA's Rosetta mission. On the right, about the same scale and resolution - Deimos.
#mars #phobos #deimos -
A tale of two terminators. The terminator is the line between sunlit and unlit sides of a body. The one at left in this image is the kind of terminator we might expect on an asteroid... covered with craters. We have seen quite a few very small rubble-pile asteroids recently (Bennu, Ryugu, Itokawa) but larger bodies... we expect hem to have craters. This one is Lutetia imaged by ESA's Rosetta mission. On the right, about the same scale and resolution - Deimos.
#mars #phobos #deimos -
The region lacking grooves faces backwards in Phobos's orbit. If there is a causal relationship between the grooves and the orientation of Phobos, does that suggest tidal effects are pulling Phobos apart? Or is it that the moon occasionally pushes its way through clouds of debris from large impacts on Mars? There's no clear answer yet to the formation of these enigmatic features. What about Deimos? #mars #phobos #deimos
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The region lacking grooves faces backwards in Phobos's orbit. If there is a causal relationship between the grooves and the orientation of Phobos, does that suggest tidal effects are pulling Phobos apart? Or is it that the moon occasionally pushes its way through clouds of debris from large impacts on Mars? There's no clear answer yet to the formation of these enigmatic features. What about Deimos? #mars #phobos #deimos
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People have been arguing about this pattern for years. In some areas it is rather disordered - central part of the top map especially. One region is devoid of grooves - central part of the bottom map. The main pattern as far as can be seen here appears to radiate away from the middle of the top map, cross the boundary and converge on the region lacking grooves, fading out before they get there. Mars Express filled in gaps later to help with this.
#mars #phobos #deimos -
People have been arguing about this pattern for years. In some areas it is rather disordered - central part of the top map especially. One region is devoid of grooves - central part of the bottom map. The main pattern as far as can be seen here appears to radiate away from the middle of the top map, cross the boundary and converge on the region lacking grooves, fading out before they get there. Mars Express filled in gaps later to help with this.
#mars #phobos #deimos -
Here is a global map of Phobos in two opposite hemispheres - well, not spheres but you know what I mean. It's the same projection as the one we saw for Mariner 9 images. The map shows areas only seen in low resolution images and 4 areas seen in high resolution frames. The image is a photomosaic of Phobos made from Viking images. Grooves show up very clearly in some areas, and if you enlarge the image more can be seen. What pattern is revealed?
#maps #mars #phobos #deimos -
Here is a global map of Phobos in two opposite hemispheres - well, not spheres but you know what I mean. It's the same projection as the one we saw for Mariner 9 images. The map shows areas only seen in low resolution images and 4 areas seen in high resolution frames. The image is a photomosaic of Phobos made from Viking images. Grooves show up very clearly in some areas, and if you enlarge the image more can be seen. What pattern is revealed?
#maps #mars #phobos #deimos -
Here is another view from later in the mission. Individual images are great for looking at the morphology of the grooves, but you need a global map to understand the pattern of grooves. The first such map was made by Peter Thomas of Cornell for his PhD. These grooves set many of us looking for grooves elsewhere... other bodies have a few groove-like features but only Saturn's Epimethius has as many as Phobos.
#mars #phobos #deimos -
Here is another view from later in the mission. Individual images are great for looking at the morphology of the grooves, but you need a global map to understand the pattern of grooves. The first such map was made by Peter Thomas of Cornell for his PhD. These grooves set many of us looking for grooves elsewhere... other bodies have a few groove-like features but only Saturn's Epimethius has as many as Phobos.
#mars #phobos #deimos -
Let's see some more of these grooves. This set of images is from Viking Orbiter 1. Are all the grooves even formed by the same process or event? They don't all look the same, and some cross others. Some look like crater chains - are they strings of secondary impact craters or drainage pits where loose surface material has fallen into a fracture?
#mars #phobos #deimos -
Let's see some more of these grooves. This set of images is from Viking Orbiter 1. Are all the grooves even formed by the same process or event? They don't all look the same, and some cross others. Some look like crater chains - are they strings of secondary impact craters or drainage pits where loose surface material has fallen into a fracture?
#mars #phobos #deimos -
NASA’s Perseverance Captures Phobos and Earth
▶️ 1 new picture from NASA (Website) https://commons.wikimedia.org/wiki/File:NASA%E2%80%99s_Perseverance_Captures_Phobos_and_Earth_%28PIA26758%29.png
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NASA’s Perseverance Captures Phobos and Earth
▶️ 1 new picture from NASA (Website) https://commons.wikimedia.org/wiki/File:NASA%E2%80%99s_Perseverance_Captures_Phobos_and_Earth_%28PIA26758%29.png
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How could such bizarre features form? are they on the surface. produced by crater ejecta, or are they the surface expression of deep fractures? There are lots of hypotheses - even ejecta from craters on Mars has been invoked, even the idea that boulders rolling across the surface could make grooves... (I can't believe that one). One image is not enough. To understand these features, the global pattern must be mapped - so we need more images.
#mars #phobos #deimos -
How could such bizarre features form? are they on the surface. produced by crater ejecta, or are they the surface expression of deep fractures? There are lots of hypotheses - even ejecta from craters on Mars has been invoked, even the idea that boulders rolling across the surface could make grooves... (I can't believe that one). One image is not enough. To understand these features, the global pattern must be mapped - so we need more images.
#mars #phobos #deimos -
The Viking missions gave us much more detail for Phobos and Deimos - we will start with Phobos. The Viking orbiters took some early images of Phobos which were a bit better than Mariner 9 managed, but this image was a game-changer. It is from Viking Orbiter 2's 39th orbit. Actually it's a mosaic of 2 frames. When it appeared in a JGR special issue on Viking in 1977 it shocked a lot of us. This is the discovery image of the famous grooves of Phobos.
#mars #phobos #deimos -
The Viking missions gave us much more detail for Phobos and Deimos - we will start with Phobos. The Viking orbiters took some early images of Phobos which were a bit better than Mariner 9 managed, but this image was a game-changer. It is from Viking Orbiter 2's 39th orbit. Actually it's a mosaic of 2 frames. When it appeared in a JGR special issue on Viking in 1977 it shocked a lot of us. This is the discovery image of the famous grooves of Phobos.
#mars #phobos #deimos -
And my Morphographic map projection of the same data. The projection is designed to show the shape of the body (in this case the convex hull of the body) as well as the locations of surface features on it.
You can't tell much about Deimos from these images. It took the next mission, Viking, to really make a difference.
#maps #mars #phobos #deimos -
And my Morphographic map projection of the same data. The projection is designed to show the shape of the body (in this case the convex hull of the body) as well as the locations of surface features on it.
You can't tell much about Deimos from these images. It took the next mission, Viking, to really make a difference.
#maps #mars #phobos #deimos -
I didn't find Blunck's map of Deimos yet - it is in the first edition of his 'Mars and its satellites', but I donated my copy of it to our map library. However... here is my photomosaic of Deimos showing image coverage by Mariner 9. This is the cylindrical projection, with zero longitude in the middle.
#maps #mars #phobos #deimos -
I didn't find Blunck's map of Deimos yet - it is in the first edition of his 'Mars and its satellites', but I donated my copy of it to our map library. However... here is my photomosaic of Deimos showing image coverage by Mariner 9. This is the cylindrical projection, with zero longitude in the middle.
#maps #mars #phobos #deimos -
Deimos looks smooth compared with Phobos. Its mean diameter is only about 12 km. Phobos is nearly twice as big - mean diameter about 22 km. Phobos has been seen by multiple orbiters but Deimos, further out, has been less seen in closeup. See the little crater on its own in the truncated image? - it's near the north pole. Until the UAE's Hope orbiter imaged it in March 2023, that was the only image of that crater (except 1 Viking image of it on the limb).
#mars #phobos #deimos -
Deimos looks smooth compared with Phobos. Its mean diameter is only about 12 km. Phobos is nearly twice as big - mean diameter about 22 km. Phobos has been seen by multiple orbiters but Deimos, further out, has been less seen in closeup. See the little crater on its own in the truncated image? - it's near the north pole. Until the UAE's Hope orbiter imaged it in March 2023, that was the only image of that crater (except 1 Viking image of it on the limb).
#mars #phobos #deimos -
I am well aware that Phobos is a very cute little moon, but its companion wins the prize for cutest moon in my view. Here is the entire imaging dataset for Deimos from Mariner 9. It's not easy to tell, just looking at this, how much of its surface was observed. For that we need a map, but Duxbury didn't draw one. I think Jurgen Blunck drew the first map of Deimos. I will try to find it. It has some gaps...
#mars #phobos #deimos -
I am well aware that Phobos is a very cute little moon, but its companion wins the prize for cutest moon in my view. Here is the entire imaging dataset for Deimos from Mariner 9. It's not easy to tell, just looking at this, how much of its surface was observed. For that we need a map, but Duxbury didn't draw one. I think Jurgen Blunck drew the first map of Deimos. I will try to find it. It has some gaps...
#mars #phobos #deimos -
0 longitude, the prime meridian, is in the middle and 180 is at the far ends. That's also true of the cylindrical projection. The zero meridian always points at Mars. 180 faces away. This has a bearing on site selection for a lander: if you land near zero longitude, you are out of contact with Earth for half an orbit because you face away from Earth, and also when blocked by Mars itself. Land at 180 and you have much better communication conditions.
#mars #phobos #deimos -
0 longitude, the prime meridian, is in the middle and 180 is at the far ends. That's also true of the cylindrical projection. The zero meridian always points at Mars. 180 faces away. This has a bearing on site selection for a lander: if you land near zero longitude, you are out of contact with Earth for half an orbit because you face away from Earth, and also when blocked by Mars itself. Land at 180 and you have much better communication conditions.
#mars #phobos #deimos -
There are other innovations available today including new map projections for non-spherical worlds. This was my PhD project. In truth no new projections have been widely adopted. Here is my morphographic projection - it's like Lambert's Azimuthal Equal Area or Equidistant but modified to show the cross-section shape of the body by allowing the radius to vary from place to place. The shape model used is the convex hull of the true shape.
#maps #mars #phobos #deimos -
There are other innovations available today including new map projections for non-spherical worlds. This was my PhD project. In truth no new projections have been widely adopted. Here is my morphographic projection - it's like Lambert's Azimuthal Equal Area or Equidistant but modified to show the cross-section shape of the body by allowing the radius to vary from place to place. The shape model used is the convex hull of the true shape.
#maps #mars #phobos #deimos -
Tom Duxbury's map was a line drawing. I wanted to do better by making a global photomosaic of Phobos using Mariner 9 images. That would have been very hard in 1974 - only a rudimentary shape model, and we have more capable software today. Using a modern shape model and image-warping software using up to 200 tie points per image in thin plate spline mode, I warped each image into a cylindrical projection and then mosaicked them together. AI eat your heart out!
#maps #mars #phobos #deimos -
Tom Duxbury's map was a line drawing. I wanted to do better by making a global photomosaic of Phobos using Mariner 9 images. That would have been very hard in 1974 - only a rudimentary shape model, and we have more capable software today. Using a modern shape model and image-warping software using up to 200 tie points per image in thin plate spline mode, I warped each image into a cylindrical projection and then mosaicked them together. AI eat your heart out!
#maps #mars #phobos #deimos
