A shows some cavity shapes which may have collected water. B shows another dam, approximately parabolic.
This shows many hollow hills in stages of collapse, A is approximately symmetric perhaps also using this crater as a dam. C also seems to use a crater, it is unlikely an impact would not break the side of the rim even as the hill collapsed into a pit. There is also missing ejecta, perhaps used to build the hills. D is more intact but has collapsed on the right side, E is collapsed to the point of being flat ground. F goes further to collapse to a pit, the pale material should be the same as that for the rooms and ceilings.
In this HiRise image of Cymhh202 A shows the pit edge, B confirms this pale material is forming walls and rooms. C shows a ridge which may be an interior support. D shows how the pit edge turns to join the interior support ridge.
This shape is unnatural, approximately like an eye. A shows the pit edge appears to have a skin broken off like the hill collapsed leaving it up in the air. This was also seen in many collapsed hollow hills in Hecates. B shows a narrow groove like an entrance. C shows the bottom of this hill, still sharp like some dam walls. D shows how this pale material is attached to the ridge like some rooms are.
This shows another HiRise image, A is a collapsed hill. B shows a collapsed hill at 9 o’clock and one collapsed on the edges at 1 o’clock. C shows two more collapsed hills as does D. E shows many collapsed hills. F shows a hill more intact on the upper side and collapsed on the lower side, G is more complete. H shows a partially collapsed hill on the lower side at 7 o’clock.
A shows an internal ridge. B shows cracks in the pale material like the floor is breaking up. If there were walls here they have eroded away perhaps leaving dark cracks in the floor. C shows a less eroded area like rooms, it appears to vary in height.
There is an impression here from the shadows of three dimensional room shapes. A shows a wall at 2 o’clock, at 10 and 12 o’clock there appears to be a squarish shape under the pale material. This may have collapsed as higher rooms eroded covering these in part. B looks to be two long narrow rooms at approximately 45 degrees from horizontal. E also looks like three long narrow rooms. C is like a recess in the rock, D may be two more long narrow rooms. It seems unlikely to be an optical illusion as the light and dark areas are consistent with shadows.
These walls are more like a tetrahedron than cubes, A shows bare walls and a nexus of walls partially covered by ceiling material. B also shows a nexus of walls with hollows around it. Six walls appear to come together at C. D shows a triangle of walls with one bisecting the base. E shows a corner of two walls with a hollow inside, between D and F it is like a rectangular shallow box suspended by some walls.
This shows the possible squarish shape suspended by other walls.
This shows how straight some of the other walls are.
This shows the pale material eroding away to nothing, forming an empty pit. B and C show part of the wall still standing.
Another hill having collapsed, the pale material would be more walls and rooms. A shows where the hill has collapsed. Bis a squarish shape also collapsed with pale material inside. C shows more pale material. D shows a crack in the intact wall perhaps from the strain of the other parts having collapsed.
A shows an intact part of the hill, B the edge where it collapsed. C shows a peak of the hill at 8 o’clock and a collapsed area at 9 o’clock. D shows two room areas, at 4 o’clock there are several intact rooms. At 8 o’clock there are walls.
A shows an interior support and T junction, probably a right angle. B shows a wall in good condition yet the hill above it has collapsed, C shows another wall. D at 4 and 10 o’clock shows another wall. D at 8 o’clock shows another wall coming from a T junction. E shows more walls, there are pale squarish shapes like the eroding floors of rooms on the edges of the pit.
The lines show how straight parts of the formation are.
A may be a crack. B and C shows a meandering line like a road or tunnel through the hill. It is unlikely to be a crack because of its even width as if it is open the whole way. Also cracks tend not to meander.
This looks like a floor that is eroding, the dark lines might be where walls had fitted into the floor. C shows a pit with no floor material, D shows the edge of the floor with these dark lines.
A shows more walls and room shapes, B, C and E show the pale edges of this material. D shows the intact part of the hill.
A and B show the edges of this collapsed area, under this the hill appears intact. C looks like a crack or it has broken a layer here. D shows where this ceiling material is eroding. E F and G show more erosion of this.
A and B show more hills collapsed, C is less eroded but perhaps collapsed in the middle. D at 2 o’clock shows a pit on the side of a crater, this is hard to explain as it looks like the pit came after the crater. It encroaches over the round shape of it. If the hills are so fragile they can collapse by themselves, then an impact should have collapsed all of it, but one corner remains standing. E shows a collapsed hill at 10 o’clock and an intact hill at 6 o’clock.
This shows either tubes or internal supports from a hill, it has a different shape with more right angles to other internal supports. A appears to show collapsed parts of the tubes. B has a groove along it like a collapsed tube. D has 5 parallel tubes running off this, they may end or go to other habitats underground. C is likely to be another tube.
A shows how the internal support, B connects to it. C appears to be eroded walls. E is the edge of the collapsed hill. D may be a tube or internal support as with F and G.
A shows an internal support, B and C show how the collapsed edge has pale materials on the inside.
A shows some wall shapes in a cavity, B shows some layers which seem to have broken off. The layers then may have protected the roof of the hollow hill, when this skin decayed the softer material under this collapsed. This is similar to the hollow hills when they collapsed in Hecates. C also shows these broken layers. D shows the layer at 10 o’clock and a collapsed cavity is at 12 o’clock. E shows the edge of the hill and how it connects to this interior support, at H at 8 o’clock, that goes all the way over to the other side of the hill. F shows possibly the peak of the former hill, G and H at 6 o’clock shows pale material that may have been rooms.
A at 6 o’clock show a hill that has collapsed, at 8 o’clock another shows no signs of collapse. The layers shown may be the key to this, as the skin peeled off the hill began to collapse. B shows an area of the large hill that forms a cavity, the pale material in close ups is usually rooms. Some may not be, for example there may be a pale layer of material in the ground that is used in walls but in some hills may be undisturbed. C shows an edge at 5 o’clock and a possible collapse at 3 o’clock. D may show settled areas, the crater may also have been repaired around it. E shows another collapsed area and possible settled parts of the roof. Engineers may be able to calculate from modeling these hills how they might collapse, and what that implies about interior supports in them. These usually seem to be too low to hold up the roof, they may then be like domes with no real support under them. The interior supports might hold the hill from spreading which could cause the roof to flex.
More examples of how these walls form rooms, A shows a T junction going down to E at 10 o’clock. Other walls appear to crisscross each other, this may to give internal support to stop the hill edges from flexing. E at 2 o’clock shows a wall with a flat surface and apparent railings, this could have been used like a road so these upturned edges prevented the creatures from falling off. These are very faint, however many of these ridges like roads have these higher edges like former walls. D shows how these extend to the edge of the hill, perhaps to connect to external tubes and roads. C to F may have been a room if these walls were higher. B shows a collapsed area with a wall inside it.
A at 7 o’clock and B shows a collapsed hill with much more of this pale material, it may be this was multiple floors of rooms. A at 2 o’clock shows more wall shapes as if this hill is much more eroded. C is another example, the pale material may have lost its dark outer skin and have quickly collapsed on the right side. This large pit at D at 4 o’clock and E at 1 o’clock has no signs of pale material and may have been completely hollow. If so then there were no interior supports helping to hold up the roof, this is also found in the Hecates area though most have some internal supports. These also were often low and would not have reached up to the roof.
A shows a pit at 12 o’clock connected with a tube to the more intact hill at 2 o’clock. At 9 o’clock there is another collapsed hill. B and C show many imprints like collapsed hills except there is only a shallow pit. These may have filled in over time from dust storms, the roof material could have filled them up, or some did not have a pit under them perhaps because the ground was harder to excavate. Engineers might be able to estimate how much material was in these roofs and how much of a pit would be filled by it.
A, B, C, and D show the faint edges of a pit. A and C have sharp edges as if made of stronger material more resistant to erosion. The inside of the pit is also much smoother with no large rocks like outside. This would be a likely outcome if the area had been cleared as a construction technique for the hill, some rocks might come up from underground over time but not as many as outside this. There is a faint impression of some walls and rooms laid out on this, it may also be a cement pad highly eroded and covered in the same soil as outside it. E shows a curved wall at 4 o’clock, there may have been a rectangular room at 10 o’clock, and another at 2 o’clock. If large enough a cleared area like this might be a good landing spot for a rover to explore the area.
This is a closeup of the previous upper left corner, there is a definite impression of a wall going from A to C and some parts appear to be higher like a cement pad. B also appears higher, the texture of the ground is also different to outside this. If this is cement then rocks would not come from underground, but some might form as the cement broke up.
This is a closeup of the curved wall mentioned earlier, A show this wall is broken at 4 o’clock. B and C show a curve which is close to two parabolas. D shows this part of the wall is breaking up on the right into separate rocks.
This shows two parabolas superimposed on the curved wall, the latis rectums are approximately parallel and form a rectangle as they join to the apex of each other. This would be a simple way to build a curved wall so the two curves line up with each other.
Here the wall is also well preserved, A at 9 o’clock may have been a small hill. Between the B lines appears to be a break in the wall. C may show three walled areas. D shows a continuation of a possibly collapsed tube with a hollow inside as 12 o’clock, this extends from C at 2 o’clock. D at 5 and 7 o’clock may also show smaller walls at right angles to the main wall pointing downwards.
A may show small rooms with walls, some have right angles. B at 11 o’clock shows a flat area like a room, at 1 o’clock there is another wall. C shows a curved wall at 10 o’clock and a straight wall at 7 o’clock. D shows a smoothly curved corner leading to a straight wall at 7 o’clock, F shows a fork into two walls. E shows an inner and outer wall here with a hollow in between like a road with railings.