Method for Identifying Lava Tubes Among Pit Craters Using Brightness Profile Across Pits on the Moon or Mars

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  • ABSTRACT

    Caves can serve as major outposts for future human exploration of the Moon and Mars. In addition, caves can protect people and electronic equipment from external hazards such as cosmic ray radiation and meteorites impacts and serve as a shelter. Numerous pit craters have been discovered on the Moon and Mars and are potential entrances to caves; the principal topographic features of pit craters are their visible internal floors and pits with vertical walls. We have devised two topographical models for investigating the relationship between the topographical characteristics and the inner void of pit craters. One of our models is a concave floor void model and the other is a convex floor tube model. For each model, optical photographs have been obtained under conditions similar to those in which optical photographs have been acquired for craters on the Moon and Mars. Brightness profiles were analyzed for determining the profile patterns of the void pit craters. The profile patterns were compared to the brightness profiles of Martian pit craters, because no good-quality images of lunar pit craters were available. In future studies, the model profile patterns will be compared to those of lunar pit craters, and the proposed method will likely become useful for finding lunar caves and consequently for planning lunar bases for manned lunar expeditions.


  • KEYWORD

    Moon , Mars , pit crater , lava tube , cave

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  • [Fig. 1.] Two types of pit crater models. (a) A concave floor void: there is no additional inner void and the floor has a concave shape. (b) A convex floor tube: there is additional inner void of a cave and the floor is in the shape of a cone that forms as the ceiling collapses.
    Two types of pit crater models. (a) A concave floor void: there is no additional inner void and the floor has a concave shape. (b) A convex floor tube: there is additional inner void of a cave and the floor is in the shape of a cone that forms as the ceiling collapses.
  • [Fig. 2.] Schematic of the pit crater model. The yellow box is a topographical model and the upright position above the model is Position 0. The 12 o’clock position is assumed with Position 0 at the center. (a) Both the light source and camera are at Position 0. (b) The light source is at Position 7 and the camera is at Position 0. (c) The light source is at Position 0 and the camera is at Position 3. (d) The light source is at Position 3 and the camera is at Position 6.
    Schematic of the pit crater model. The yellow box is a topographical model and the upright position above the model is Position 0. The 12 o’clock position is assumed with Position 0 at the center. (a) Both the light source and camera are at Position 0. (b) The light source is at Position 7 and the camera is at Position 0. (c) The light source is at Position 0 and the camera is at Position 3. (d) The light source is at Position 3 and the camera is at Position 6.
  • [Fig. 3.] The brightness profile of the flat surface topographical model. No diffusion effect is observed in this case. In the righthand plot, the x axis is the distance along the red line in the left-hand image, and the y axis is the brightness intensity.
    The brightness profile of the flat surface topographical model. No diffusion effect is observed in this case. In the righthand plot, the x axis is the distance along the red line in the left-hand image, and the y axis is the brightness intensity.
  • [Fig. 4.] The images of the concave floor void model and the corresponding brightness profiles, for different scenarios. The arrangements of the light source and the camera for (a) through (d) are shown in Figs. 2a through 2d, respectively. The brightness profiles correspond to the light intensity along the red lines in the corresponding optical images of the topographical model. In addition, for each brightness profile, the region between the red vertical bars corresponds to the internal region of the pit crater. The x axis is the distance along the red line and the y axis is the light intensity.
    The images of the concave floor void model and the corresponding brightness profiles, for different scenarios. The arrangements of the light source and the camera for (a) through (d) are shown in Figs. 2a through 2d, respectively. The brightness profiles correspond to the light intensity along the red lines in the corresponding optical images of the topographical model. In addition, for each brightness profile, the region between the red vertical bars corresponds to the internal region of the pit crater. The x axis is the distance along the red line and the y axis is the light intensity.
  • [Fig. 5.] The images of the convex floor tube model and the corresponding brightness profiles. The arrangements of the light source and the camera for (a) through (d) are shown in Figs. 2a through 2d, respectively. The brightness profiles correspond to the light intensity along the red lines in the corresponding optical images of the topographical model. In addition, for each brightness profile, the region between the red vertical bars corresponds to the internal region of the pit crater. The x axis is the distance along the red line and the y axis is the light intensity.
    The images of the convex floor tube model and the corresponding brightness profiles. The arrangements of the light source and the camera for (a) through (d) are shown in Figs. 2a through 2d, respectively. The brightness profiles correspond to the light intensity along the red lines in the corresponding optical images of the topographical model. In addition, for each brightness profile, the region between the red vertical bars corresponds to the internal region of the pit crater. The x axis is the distance along the red line and the y axis is the light intensity.
  • [Table 1.] Pit craters on Mars (http://www.uahirise.org)
    Pit craters on Mars (http://www.uahirise.org)
  • [Fig. 6.] The images of pit craters on Mars and their corresponding brightness profiles. The images in (a) and (b) show the pit craters on Mars, photographed by HiRISE. The name of the image and the scale are included. The brightness profiles on the right show the light intensity along the red lines in the corresponding optical images. The x axis is the distance along the red line and the y axis is the light intensity.
    The images of pit craters on Mars and their corresponding brightness profiles. The images in (a) and (b) show the pit craters on Mars, photographed by HiRISE. The name of the image and the scale are included. The brightness profiles on the right show the light intensity along the red lines in the corresponding optical images. The x axis is the distance along the red line and the y axis is the light intensity.