We discovered a lot of lava tube skylights of all shapes and sizes near our habitat, and were actually able to enter one of them on a recent EVA. I thought I’d give a summary of that EVA here, along with lots of photos we took along the way.
The objectives of EVA 29, conducted on Wednesday, June 12, were to photo-map the west wall of the lava tube skylight #1 (the northern of the two large skylights; Fig. 1), scout numerous suspected small skylights in the area, attempt to traverse back to the hab across the east lava field, and acquire photos and collect samples along the route. Also, approval was granted by Mission Support to enter one or more small skylights if judged safe.
A GPS track of EVA 29 is shown in Fig. 2. One of the pre-established access routes was followed to skylight 1, with a quick stop at a seismic monitoring station at waypoint EVA29-05. Skylight #1 was approached from the east, and its west wall was photomapped (Fig. 3, top) and assessed for possible descent routes. The conclusion was that although it may be possible to downclimb into the skylight near the midpoint of the west wall, it would be unwise to attempt that in simulated spacesuits, at least without climbing equipment. Another view of Skylight #1 is shown in the bottom panel of Fig. 3.
A small skylight at waypoint EVA29-08, previously identified on EVA 18, was visited (Fig. 4), but a decision was made not to attempt to enter. The depth of the skylight was just over ~1 m, making it relatively easy to descend into; however, getting out may have presented difficulties and possible damage to the suits.
The traverse between skylights 1 and 2 along a new route was relatively easy, and almost entirely on pahoehoe flows. A small skylight at waypoint EVA29-10 (just north of Skylight 2; Fig. 5) was visited, but was clearly impossible to enter safely.
After traversing along the east rim of skylight #2 (Fig. 6), a decision was made to skip the skylight at waypoint EVA29-11, which did not look friendly in aerial photos, and proceed directly to waypoint EVA29-12. This turned out to be the correct decision – a major finding of this EVA is that the skylight at waypoint EVA29-12 can be safely entered and its lava tube can be easily accessed (Fig. 7). The EVA team descended to the floor of the skylight and entered ~5 m into the lava tube (Fig. 8). Samples of the white substance(s) coating the walls were collected from an inconspicuous location near the floor of the lava tube. It appears possible to proceed significantly further into the lava tube, and a future EVA to this location is being planned.
Numerous small collapse pits were noted in the area SSW of skylight 2 (Fig. 9a), which were too small to enter and did not appear to connect to major lava tubes. Another skylight was visited at waypoint EVA29-13 (Fig. 9b). Its steep walls, unstable overhangs at the rim, and a significant depth of at least ~15 m earned it the nickname “The Death Pit”.
The westward traverse to the hab across the lava fields was long but relatively straightforward. The most challenging stretch is the crossing of an aa lava flow just west of waypoint EVA29-15. The flow is ~30 m across and requires extreme care to cross safely. A deviation from the pre-planned route was made as the EVA team approached the cinder cone ridge. The slopes at the planned crossing point were too steep to traverse, and a detour to the north, where the slopes were gentler, was made.
Figure 7. Entrance to the lava tube at waypoint EVA29-12. Photo by Kate Greene.
Figure 9. (a) One of numerous small (~ 1 m in depth and diameter) collapse pits encountered during the EVA. (b) Skylight at waypoint EVA29-13, characterized by steep walls, unstable overhangs, and a depth of at least ~15 m. Nicknamed “The Death Pit”.