MINERALOGY, SPECTROSCOPY AND GEOCHEMISTRY OF BASALTIC DRILL CORE FROM HUMU'ULA SADDLE, HI: IMPLICATIONS FOR SUBSURFACE ALTERATION ON MARS

In this session, we will present the mineralogy, spectroscopy and geochemistry of two drill cores, PTA2 and KMA1, from the Humu’ula Saddle of Hawaii as analogs to subsurface alteration on Mars. Short wave and long wave spectral characteristics, along with higher resolution validation data of the PTA2 drill core show moderate hydrothermal alteration of mainly olivine distributed among the pore spaces and fractures of the rock. Alteration minerals included Fe-Mg smectites and zeolites, which are indicative of low to moderate temperatures, in neutral to sub basic pH conditions, within the subsurface. Further study of the mafic mineralogy in both spectroscopic and petrographic analysis suggest the rock-water interactions occurred in a chemically closed system. These observations are similar to chemical compositions of clay bearing units on Mars, such as those examined in Dr. Bishop’s case study of the Libya Montes Region and Coprates Catena (Bishop 2013, Weitz and Bishop 2016). They are also similar to minerals inferred to have been formed in the subsurface that have been exposed at the surface through impact gardening (Ehlmann 2011, Poulet 2008).

The spectroscopic examination of the KMA1 hole will commence this summer and is anticipated to yield different results than PTA2. These differences may be reflected in the stratigraphy and groundwater data from KMA1. The similarities and differences between these Hawaiian drill cores, and their alteration mineralogy, will offer exciting insight into early Martian subsurface hydrothermal environments.