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[MIS12-P02] Possible existence of lava tube cave and pit/fissure cave in the Moon and Mars
Keywords:Lava flow, Lava tube cave, Pit cave, Moon, Mars
[Introduction]
There is a large number of lava tube caves(~150) on the foot of Mt. Fuji, though there are also some fissure/pit crater caves(~4)[1,2]. It is also thought that the lava tube cave is preponderant because of the vast lava flow on the Moon and the Mars, but the possibility of the existence of the fissure/pit crater cave cannot be denied. We compared the lava tube cave such as Banba ana cave and fissure/pit crater cave such as Kaminari ana cave on Mt.Fuji, then, examined the possible existence of fissure/pit crater caves on the Moon and Mars.
[Comparison of lava tube cave/Banba ana cave and fissure cave/Kaminari ana cave]
As shown in Fig. 1 and 2, horizontal cavities communicate with the vertical hole for both caves.
Banba ana cave has,under the32m-deep vertical hole. a tubular cavity of length of 1 km. Banba ana cave is formed in Futagoyama/Anmoyama lava flow erupted from the fissure vent of Futagoyama. Banba ana cave has lava shelves, ropy lava flow, and lava stalactite inside of the tubular cavity, indicating the characteristics of a typical lava tube cave(Photo 1). The obtained lava yield strength fB=H(ρg sinα)/4 of 3.4x103 to 6.8x103Pa for the slope angle:4.8°and for the tube height 5m to 10m,is a reasonable value as a basalt.
Kaminari ana cave was formed in Kansuyama lava flow under with the vertical hole depth of 10 m. Kaminari ana cave has a horizontal fissure cavity of height of 3m to 6m with a width of 7m. it is a part of the fissure/pit vent. In the fissure/pit cavity of Kaminari ana cave, a scoria layer can be seen behind the collapsed side wall of the fissure cavity at the bottom (Photo 2). This cavity can be regarded as a fissure cave created by draining back of magma.
[Possibility of pit/fissure vent cave on the Moon/Mars]
The cavity height(H=4fB/(ρg sinα)) as a lava tube cave is estimated for the vertical holes of the Moon and Mars[3,4,5]. For Lacus Mortis Pit in the Moon, the estimated tube height as the lava tube cave deviates greatly in comparison to the vertical hole depth (estimated tube height 2.5 m~9.8 m for a vertical hole depth of 112 m), so the cavity could be a pit/fissure cave where magma is drained back[3]. As for Arsia Mons on the Mars[4], the estimated value for the vertical hole on the steep slope of Arsia Mons (slope angle 1.0°~3.5°) has a large deviation from the vertical hole depth, so that there is a possibility to be a pit/fissure cave. On the other hand, the vertical holes on the gentle slope on the foot of Arsia Mons (slope angle 0.12° to 0.54°) show almost the same value as the estimated tube height, suggesting that a lava tube cave is likely to exist. Regarding Elysium Mons[5], for the vertical holes on the steep slope of Elysium Mons (slope angle ~6°), the difference between the vertical hole depth and the estimated tube cavity height is large, so it may be a pit/fissure cave.
[Conclusion]
Exploration of the internal structure of the vertical hole in order to clarify how the cavity under the vertical hole of the Moon and Mars is necessary at first for understanding the igneous activity and for possible future use as human base. It is expected that the fissure/pit cave and the lava tube cave will clarify the eruption mechanism and the behaver of lava flow after the eruption. In any case, both the lava tube cave and fissure/pit cave will be possible as underground bases of the Moon and Mars in the future.
References:
[1]Takanori Ogawa (1991): Volcanic cave of Fujimiya, Fujimiya City Folk Museum, Fujimiya City Board of Education, [2]Takanori Ogawa (1991): Volcanic cave at the southern foot of Fuji, Susono city Education Committee,
[3]Tsutomu Honda(2019): PPS08-P0 Cave height of lava tube cave under the vertical hole estimated from the surface topography of the Moon, Japan Geoscience Union 2019 Meeting, [4]Tsutomu Honda(2017): P117 Mars Possibility of Lava Tube Cave in Vertical Hole of Asia Mons, Japan Volcanic Society Autumn Meeting,[5]Tsutomu Honda(2018): SVC43-P02 Lava yield strength and possibility of lava tube cave below the vertical hole of Mars Elysium volcano, Japan Geoscience Union 2018 Meeting
There is a large number of lava tube caves(~150) on the foot of Mt. Fuji, though there are also some fissure/pit crater caves(~4)[1,2]. It is also thought that the lava tube cave is preponderant because of the vast lava flow on the Moon and the Mars, but the possibility of the existence of the fissure/pit crater cave cannot be denied. We compared the lava tube cave such as Banba ana cave and fissure/pit crater cave such as Kaminari ana cave on Mt.Fuji, then, examined the possible existence of fissure/pit crater caves on the Moon and Mars.
[Comparison of lava tube cave/Banba ana cave and fissure cave/Kaminari ana cave]
As shown in Fig. 1 and 2, horizontal cavities communicate with the vertical hole for both caves.
Banba ana cave has,under the32m-deep vertical hole. a tubular cavity of length of 1 km. Banba ana cave is formed in Futagoyama/Anmoyama lava flow erupted from the fissure vent of Futagoyama. Banba ana cave has lava shelves, ropy lava flow, and lava stalactite inside of the tubular cavity, indicating the characteristics of a typical lava tube cave(Photo 1). The obtained lava yield strength fB=H(ρg sinα)/4 of 3.4x103 to 6.8x103Pa for the slope angle:4.8°and for the tube height 5m to 10m,is a reasonable value as a basalt.
Kaminari ana cave was formed in Kansuyama lava flow under with the vertical hole depth of 10 m. Kaminari ana cave has a horizontal fissure cavity of height of 3m to 6m with a width of 7m. it is a part of the fissure/pit vent. In the fissure/pit cavity of Kaminari ana cave, a scoria layer can be seen behind the collapsed side wall of the fissure cavity at the bottom (Photo 2). This cavity can be regarded as a fissure cave created by draining back of magma.
[Possibility of pit/fissure vent cave on the Moon/Mars]
The cavity height(H=4fB/(ρg sinα)) as a lava tube cave is estimated for the vertical holes of the Moon and Mars[3,4,5]. For Lacus Mortis Pit in the Moon, the estimated tube height as the lava tube cave deviates greatly in comparison to the vertical hole depth (estimated tube height 2.5 m~9.8 m for a vertical hole depth of 112 m), so the cavity could be a pit/fissure cave where magma is drained back[3]. As for Arsia Mons on the Mars[4], the estimated value for the vertical hole on the steep slope of Arsia Mons (slope angle 1.0°~3.5°) has a large deviation from the vertical hole depth, so that there is a possibility to be a pit/fissure cave. On the other hand, the vertical holes on the gentle slope on the foot of Arsia Mons (slope angle 0.12° to 0.54°) show almost the same value as the estimated tube height, suggesting that a lava tube cave is likely to exist. Regarding Elysium Mons[5], for the vertical holes on the steep slope of Elysium Mons (slope angle ~6°), the difference between the vertical hole depth and the estimated tube cavity height is large, so it may be a pit/fissure cave.
[Conclusion]
Exploration of the internal structure of the vertical hole in order to clarify how the cavity under the vertical hole of the Moon and Mars is necessary at first for understanding the igneous activity and for possible future use as human base. It is expected that the fissure/pit cave and the lava tube cave will clarify the eruption mechanism and the behaver of lava flow after the eruption. In any case, both the lava tube cave and fissure/pit cave will be possible as underground bases of the Moon and Mars in the future.
References:
[1]Takanori Ogawa (1991): Volcanic cave of Fujimiya, Fujimiya City Folk Museum, Fujimiya City Board of Education, [2]Takanori Ogawa (1991): Volcanic cave at the southern foot of Fuji, Susono city Education Committee,
[3]Tsutomu Honda(2019): PPS08-P0 Cave height of lava tube cave under the vertical hole estimated from the surface topography of the Moon, Japan Geoscience Union 2019 Meeting, [4]Tsutomu Honda(2017): P117 Mars Possibility of Lava Tube Cave in Vertical Hole of Asia Mons, Japan Volcanic Society Autumn Meeting,[5]Tsutomu Honda(2018): SVC43-P02 Lava yield strength and possibility of lava tube cave below the vertical hole of Mars Elysium volcano, Japan Geoscience Union 2018 Meeting