One of the many hats I wear on this mission is that of the Crew Geologist. My other roles include Health & Safety Officer, Information and Communications Technology Officer, EVA Planner, and Thermographer. That will probably be typical on future planetary exploration missions: due to the small crew size, each crewmember would be expected to carry out a diverse set of tasks, with some being outside of their primary specialty. As a planetary scientist, I’ve taken core courses and field practicums in geology, as well as participated in several geological field studies, but it has not been the main focus of my research.
With that in mind, one of the HI-SEAS investigators suggested an experiment to assess how long it would take for someone like myself to develop a complete picture of the petrology, mineralogy, geomorphology, and stratigraphy of the area where our habitat is located. I was specifically asked not to research the geology of the Mauna Loa region prior to my arrival here, and document my efforts to study our surroundings. This post is the first of several that will describe my progress in this area.
EVA #9 on Friday, May 3, was the first outside excursion dedicated primarily to geological exploration. The first stop was a basalt outcrop approx. 6 meters west of the hab and 6 meters north of the solar panels. The outcrop represents a cross-section of at least six distinct layers, presumably corresponding to individual lava flows. The texture is highly vesicular, almost frothy, indicating a high volatile content of the lava. Bulk density is low, at ~1.5 g cm-3. Both pahoehoe and aa flow morphologies are evident within several layers. Numerous discolorations are noted, with colors including salmon-pink, dark yellow, and reddish-brown (Fig. 1). These are likely due to a combination of weathering, oxidation, and alteration processes, and further mineralogical analysis is forthcoming. Sample #1 was collected at this site.
The EVA team then proceeded along the cinder cone ridge bearing SSW from the hab. ~25 m into the traverse, a thin lava flow with a pahoehoe texture was noticed at the base of the ridge, and part of it as collected as Sample #2 (Fig. 2). Aside from a thin redding-brown oxidation coating, the sample is fresh and unaltered, and appears black in cross-section. Numerous clasts of reddish-brown volcanic cinders are incorporated into the sample (Fig. 2b), and were presumably absorbed into the lava as it flowed over the cinder cone deposits.
Approx. 50 m into the traverse, a large aa lava flow was encountered (Fig. 3), making further passage unsafe. Significant voids or cavities were noted when examining the edge of the flow (Fig 3b), which may be indicators of a small, continuous lava tube underneath the flow. This further underscores the danger of any attempts to traverse across aa lava flow.
During one of last week’s EVAs, it was noted that lava flows visible from the hab range in color from black to light-grey, with the color of the flows likely being an indicator of their age: darker flows are generally superimposed over lighter ones. On this EVA, it was further noted that the texture of light-colored flows in the distance appears almost snow-like at the right sun angle. This EVA also afforded an opportunity to examine and sample light-colored flows up close (Fig. 3b, Fig. 4a). The initial examination revealed a thin surface coating almost pure white in color. Sample #3 was collected and examined after returning to the hab. The coating is thin, patchy, varies in thickness between ~50 and ~200 µm and is between 5 and 7 on the Mohs hardness scale. This essentially rules out lichen and is suggestive of a hard mineral surface deposit. The likely composition of this deposit will be discussed in next week’s report.
Before returning to the hab, a soil sample (Sample #4) was collected from the slope of the cinder cone adjacent (immediately east of) the hab. Examination at the hab revealed irregularly-shaped, highly vesicular volcanic cinders ranging in color from reddish-brown to black, with a mean diameter of ~5 mm and a bulk density of > ~1.3 g cm-3 . Many cinders contain patches of dark, glassy, non-vesicular material, mostly as a surface coating. A few also contain flow features, possibly suggesting that they were partly molten when deposited.
Next week’s work will focus on mineralogical identification of basalt alteration products observed in the vicinity of the hab, as well as the beginning of geological mapping.
Figure 4. a) Close-up of a white coating on basalt, taken near the same location as Fig. 3. b) Sample collected at the site, illustrating the dramatic color difference between surface coating and fresh fracture surface.