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Exploring Lava Tubes with Lidar at Craters of the Moon National Monument and Preserve, Idaho

Author: 
W. Brent Garry
Topic: 
Geology
Delivered As: 
Oral
Abstract Text: 

Lava tubes are insulated, subsurface conduits that transfer lava several meters to tens of kilometers in known terrestrial examples. Several pits have been identified on other planetary bodies including the Moon and Mars that may potentially connect to subsurface lava tube systems. These pits on the Moon are possible exploration sites for robotic and human missions. Therefore we need to test instruments and methods that could be used for exploring these pits and any subsurface systems that may be preserved. Lidar instruments have several applications to mission and science operation for exploring the lunar surface including hazard avoidance and traverse planning during investigations of pits and permanently shadowed regions. The SSERVI FINESSE (Field Investigations to Enable Solar System Science and Exploration) team has been using a terrestrial laser scanner (TLS) to document the morphology, dimensions, and textures of Indian Tunnel lava tube at Craters of the Moon National Monument and Preserve in Idaho during their 2014 and 2015 field campaigns. We surveyed 250 meters of Indian Tunnel using a Riegl Vz-400 TLS (lidar). The Vz-400 is a vertical line scanner and uses a near-infrared (NIR), class 1 (eye-safe) laser with a nominal range up to 450 m. Our final point cloud combines 22 scans of the interior and exterior surface of the lava tube system for a total of 266 million points. The key strength of using lidar to survey a lava tube is that a single data set captures details of the structure on multiple scales. A bird's-eye view of the data reveals the overall shape of the tube and a side view shows the relationship of the lava tube to the overlying surface. The interior views show individual layers of lava flow within the collapse pits, rubble from ceiling collapse on the floor of the tube, and details of flow textures on the walls, including lava drips. We have made some preliminary measurements using the point cloud. The width of the tube section that we scanned ranges from 8 to 22 m and the height ranges from 5 to 12 m. The distance between the ceiling of the tube and the surface indicates the roof thickness ranges between 0.5 to 4.0 m along the section we surveyed. The elevation of the tube floor decreases 6 m over a length of 200 m for a slope of -1.7 degrees. Flow textures, including pāhoehoe ropes on the floor of the tube and lava drips on the ceiling are also visible in the point cloud. We will detail our survey strategy, steps for processing and analyzing the data, and discuss implications for future exploration of lava tube systems on planetary bodies.

Co-Authors: 
P. Senthil Kumar: CSIR-NGRI, Hyderabad, India"...
SSERVI Identifier: 
NESF2016-053

About SSERVI
Recognizing that science and human exploration are mutually enabling, NASA created the Solar System Exploration Research Virtual Institute (SSERVI) to address basic and applied scientific questions fundamental to understanding the Moon, Near Earth Asteroids, the Martian moons Phobos and Deimos, and the near space environments of these target bodies. As a virtual institute, SSERVI funds investigators at a broad range of domestic institutions, bringing them together along with international partners via virtual technology to enable new scientific efforts."