Basaltic Caves as a Planetary Analog
Dylan Childs explores a sulfate-bearing lava cave on Mauna Loa, Hawaii
Lindsay McHenry and her students first started working in lava caves in 2007. We were first lured to the lava tubes of Crater of the Moon National Monument (Idaho) by the prospect of sampling sulfate minerals (especially jarosite) in a high-iron basaltic lava context- of interest to Mars researchers. Our investigations expanded to lava tubes at Lava Beds National Monument (California) and Hawaii. The protected environment within the caves helps to preserve delicate and soluble sulfate minerals. While we were in those caves we also took note of the “sparkly” and sometimes metallic-looking cave walls.
In 2021 we switched our emphasis to these surface veneers, formed when the lava tubes initially cooled. These veneers include a thin outer oxidized layer (mostly hematite and magnesioferrite), overlying a layer enriched in calcium and magnesium (potentially diopside) and finally basalt. In some caves, sulfate minerals also form on the surfaces. We are investigating these as a potential analog for weathering on the surface of Venus, where a basaltic lava flow would cool in a higher-temperature (and more sulfate-rich) environment than on Earth. The insulated environment of the lava tube interior, plus the associated volcanic gases, could yield a weathered surface more similar to those on Venus.
Lindsay McHenry, Dylan Childs, and Jorge Acosta document samples in a lava cave in Hawaii
Fantastic lava stalactites and stalagmites (“lavacicles”) in a Hawaiian lava tube.
SEM images (backscatter, EDS-derived element maps) of a cross-section of a surface veneer from a lava tube interior, Craters of the Moon National Monument. Iron (yellow) is concentrated in the other layer, over a layer concentrated in Mg (blue) and Ca (red), consistent with a layer rich in hematite overlying a pyroxene-rich layer.
Source: McHenry and Ruffini, 2021.
Related publications and abstracts:
Childs, D.A., Acosta, J., McHenry, L.J., 2023. Investigation of oxidation conditions within lava tubes: analogue for Venus surface geology. Lunar and Planetary Science Conference (poster), Houston, TX, March 2023.
Acosta, J.L., McHenry, L.J., 2023. Extended, high-temperature cooling of lava tube interiors: analog for Venus. Lunar and Planetary Science Conference (poster), Houston, TX, March 2023.
McHenry, L.J., Ruffini, J.J., 2021. Extended, High-Temperature Cooling of Lava Tube Interiors: Analog for Venus. Lunar and Planetary Science Conference (virtual), March 2021.
Richardson, C.D., Hinman, N.W., McHenry, L.J., Kotler, J.M., Knipe, D.L., Scott, J.R., 2012. Secondary Sulfate Mineralization and Basaltic Chemistry of Craters of the Moon National Monument, Idaho: Potential Martian Analog. Planetary and Space Science 65: 93-103. doi:10.1016/j.pss.2012.02.002
McHenry, L.J., 2008. Unusual sulfate cave mineral deposits at Craters of the Moon National Monument, Idaho: Potential analogue for Meridiani Planum, Mars. Proceedings of the 18th annual Wisconsin Space Conference, 10 pp.