Terra Johnson, “Magnetic Investigation of Oxidative Processes in Lava Tubes: Analog for Venus Surface Geology”
Mentor: Julie Bowles, Geosciences
Poster #205

Venus, with 80% of the surface covered in lava flows, is believed to be volcanically active. However, the planet’s dense, acidic CO₂ atmosphere and average surface temperature of 460℃ limit geological methods used to illustrate Venus’ surface conditions, making it challenging to determine the relative ages of lava flows. Earth’s lava tubes, which also experience oxidation in hot, vapor-rich environments similar to Venus, might serve as an analog for the planet. Venus surfaces that have not experienced significant oxidation would have similar surface mineralogy to young lava tube samples on Earth. Studying the timing, extent, and nature of oxidation may allow us to establish constraints on surface age. This project aims to use magnetic techniques to document variations in the type and abundance of magnetic minerals between unoxidized and oxidized basaltic lava surfaces in the Hawaiian 1200 Kipuka Kanohina and the 2018 Pu’u’ō’ō lava tube flows. The secondary goal is to assess if the magnetic results can aid in differentiating between high or low-temperature oxidation, which is significant in assessing the suitability of these samples as potential analogs for Venus’s surface geology. The plotted log10 distributions of the samples’ acquired isothermal remanent magnetization (IRM) allows us to determine the coercivities, or the magnetic field required to reverse the direction of magnetization, of various minerals present. The IRM plots show that the permanent magnetization of highly oxidized basalts from Hawaii lava tubes are dominated by low coercivity minerals like magnetite, rather than the anticipated hematite. These unexpected results may indicate hematite is present in the superparamagnetic domain state, where the grain’s magnetic intensities align rapidly with an applied field and the grains’ permanent magnetization relaxes quickly. This indicates that the interior less-oxidized layers have a higher superparamagnetic content and are more dominated by high coercivity minerals compared to their oxidized coatings.