University of Arizona

A multifaceted approach to investigating the magmatic and post-magmatic history of volatiles in basalts from the rim of Steno Crater

The release of sample 71036 presents a unique opportunity to study volatiles in a basalt that has been frozen and specially preserved since its return, and to compare those results with basalts of similar bulk chemistries that have been stored at room temperature. This exceptional suite of basalts also offers a chance to unravel the history of volatile loss on the Moon, from the onset of mineral crystallization through vesicle formation, sampling, and subsequent curation. This is a proposal requesting three years of funding to carry out a detailed study of the major, minor, and volatile element chemistry (including H isotopes) of H-bearing minerals and melt inclusions in four Apollo 17 basalts, and to determine the U-Pb and Ar ages of the basalts. 

The primary goals of this consortium study are to: 

  1. Compare, for the first time, the isotopic composition of and abundance of water in H-bearing minerals and melt inclusions of lunar basalts curated at room temperature and a lunar basalt that has been frozen for nearly 50 years. This will elucidate the effects (if any) of curation preparation and storage methods on the exchange of water between samples and the terrestrial atmosphere; 
  2. Compare the volatile inventories (including H isotopes and H, Cl, and S abundances) of lunar minerals and glasses from samples prepared using different sample preparation techniques to determine the effect that sample preparation has on our ability to differentiate lunar vs terrestrial volatile signatures; 
  3. Determine the mineralogy, major-element mineral chemistry, and rock textures including occurrence of vugs and vesicles, which together with H abundance and H isotope data (from goals 1+2) and S speciation will be used to evaluate critically the degassing history of lunar basalts at the Apollo 17 site; and 
  4. Define the eruption and exposure ages of each of the four basalts to determine if they are from the same lava flow. Age constraints will then allow us to place our volatile data into the wider context of the magmatic suite. 

 
Goals 1 and 2 require samples that have been prepared in indium metal, along with existing and new epoxy-mounted thin sections. Goals 1-3 will involve chemical and textural analyses of phases by scanning electron microscope and electron probe micro-analyzer, as well as chemical (H abundance) and H isotopes of suitable phases (apatite, olivine, pyroxene, melt inclusions) by secondary ion mass spectrometry (SIMS and NanoSIMS), and S speciation by S-XANES. Goal 4 consists of U-Pb dating of Zr-bearing minerals and phosphates in existing thin sections and a new thin section of 71036 by SIMS and bulk-rock Ar isotope analyses of rock fragments by laser step heating.

Relevance to NASA and Apollo Next Generation Sample Analysis. We will examine the volatile record of a cold-curated Apollo 17 basalt, as well as three other basalts collected during the same mission that were curated conventionally. The use of frozen sample 71036 is critical to the achievement of the objectives of this study and will permit quantification of the effects of different curation methods and sample preparation techniques on the indigenous H budget of the samples - an important problem to solve in preparation for future lunar missions anticipated in the 2020s and beyond. Our diverse consortium approach is required to fully understand the indigenous volatile history of this suite of basalts and will maximize the science derived from samples returned by the Apollo 17 mission almost fifty years ago.

The team includes members from the University of Arizona, Johnson Space Center.

Contact information: Jessica Barnes,  jjbarnes@email.arizona.edu

Jessica Barnes

Jessica Barnes (PI)
University of Arizona

Maryjo Brounce

Maryjo Brounce (Co-I)
University of California, Riverside

Jed Mosenfelder

Jed Mosenfelder (Co-I)
University of Minnesota

Jeremy Boyce

Jeremy Boyce (Co-I)
NASA JSC

Carolyn Crow

Carolyn Crow (Co-I)
University of Colorado, Boulder

Tom Zega

Tom Zega (Co-I)
University of Arizona

Zoe Wilbur

Zoë Wilbur (Grad student)
University of Arizona