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2011 Annual Science Report

University of Hawaii, Manoa Reporting  |  SEP 2010 – AUG 2011

Cosmochemical Search for the Origin of Water in Planetary Bodies

Project Summary

The ultimate goal of our study is to understand the origin of water in planetary bodies (asteroids, comets and terrestrial planets). In particular we want to understand better the water-based chemis-try that happens on these bodies. This gives important insights into the role(s) played by water dur-ing the origin of our Solar System. We are taking a new approach to understanding aqueous altera-tion processes in carbonaceous chondrites by investigating the distribution and composition of or-ganic compounds in aqueously altered chondrites. This research will also shed light on the nature of organic compounds in asteroids and in planetesimals that might have delivered organic compounds to the early Earth. This research will use a variety of micro-analytical techniques (optical microscopes, scanning electron microscope, electron microprobe, transmission electron microscope, ion microprobe, Raman spectroscopy) to investigate the aqueous alteration that has affected the CR chondrites. These meteorites were chosen because they exhibit a complete series of alteration, from very lightly altered to completely altered, and they have experience almost no thermal metamorphism.

4 Institutions
3 Teams
3 Publications
0 Field Sites
Field Sites

Project Progress

The ultimate goal of our study is to understand the origin of water in planetary bodies (asteroids, comets and terrestrial planets) and its role in aqueous and hydrothermal processes on these bodies. In our current project, we are focusing on carbonaceous (CV-type) and ordinary chondrites, which contain secondary minerals (e.g. fayalite, magnetite). Because these minerals formed during aqueous alteration in the asteroidal settings, they are expected to record hydrothermal processes on the CV and ordinary chondrite parent asteroids.

“Oxygen Isotopes”

We performed oxygen-isotopic measurements on fayalite and/or magnetite in CV and ordinary chondrites. The data we obtained revealed that these minerals formed in fluids with different Δ17O (Δ17O = δ17O − 0.52 × δ18O) in CV and ordinary chondrite parent asteroids. This may imply that the sources of primordial water ice were different in these two types of asteroids. In addition, we established a protocol for 53Mn-53Cr isotopic dating methods for fayalite, and obtained high precision data on CV fayalite. We are planning to measure fayalite in CV and ordinary chondrites, and constrain the timing of hydrothermal processes in their parent asteroids.

“Aqueous Alteration in Chondrites”

This project aims to study the distribution of organic molecules in CR carbonaceous chondrites in order to directly link the evolution of the organic compounds with the evolution of minerals in our Solar System. Recent work by others shows that CR1-3 chondrites have substantial concentrations of organic compounds, including amino acids, and that the mix of amino acids in them changes with the extent of aqueous alteration. This project aims to study the distribution of organic molecules in CR carbonaceous chondrites in order to directly link the evolution of the organic compounds with the evolution of minerals in our Solar System, with inferences for the processes involved on the prebiotic Earth. The results of the work will help determine the mechanisms that drive the chemical evolution that led to life on Earth. The project focuses on in situ studies of three CR carbonaceous meteorites from least to most aqueously altered. The relationship between the organic carbon and the mineral phases will be determined using state-of-the-art techniques such as, Raman microscopy, electron microprobe analysis, secondary ion mass spectrometry, and high resolution tunneling electron microscopy. Preliminary results have shown that Raman spectroscopy is an ideal way to map the presence of organic carbon in a non-destructive fashion while also identifying the mineral phases. In addition, mineralogic and petrographic information will be gathered, such as former fluid composition, fluid abundance, temperature, duration, and extent of aqueous alteration of these meteorites. Information gleaned from these four techniques will allow us to fully characterize the nature of the organic carbon present in these meteorites and its relationship with aqueous alteration of carbonaceous chondrites.

“Aqueous Alteration in Primitive Chondrites”

This study has three objectives: 1) to detail the petrographic context of aqueous alteration in CR chondrites, 2) to quantify the onset and duration of alteration, and 3) to constrain the conditions of alteration (water/rock ratio, Eh, pH). Graduate student, Christine Jilly, who is supported by NAI funds, will be doing this work as her thesis project. She has obtained a suite of CR chondrites and has been characterizing their mineralogy, petrology, and mineral chemistry using the optical microscope, scanning electron microscope, and electron microprobe. She has already discovered a very interesting feature in the Renazzo CR2 chondrite. In one small area, she found three chondrules that have undergone completely different styles of aqueous alteration (Figure). Chondrule 1 has minor replacement of metal with sulfide and partial conversion of chondrule glass to phyllosilicates. Chondrule 2 exhibits partial replacement of metal by magnetite and phosphates. The chondrule rim contains fine-grained framboidal magnetite. Chondrule 3 is rimmed with sulfides and the outer half of the chondrule has had its glass altered to phyllosilicaes. There are several important implications of this discovery: 1) the conditions of alteration were not the same throughout the CR parent body; 2) products of various environments have been intimately mixed; 3) it will be critical to ascertain which properties observed in a meteorite represent a single environment before attempting to interpret the conditions in that environment. These results will be presented at the 43rd Lunar and Planetary Science Conference in March 2012.

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Measured δD values of lunar and martian apatite crystals. The gray field denotes the δD range of meteoric water on Earth. Bars include 2σ uncertainty in δD. Data for lunar mare basalt is from published work by James Greenwood and others; other lunar samples and the martian meteorite Nakhla are our data.

    Gary Huss
    Project Investigator

    Sasha Krot
    Project Investigator

    Jeff Taylor
    Project Investigator

    kaori jogo
    Project Investigator

    Patrick Gasda
    Graduate Student

    Christine Jilly
    Graduate Student

    Objective 1.1
    Formation and evolution of habitable planets.

    Objective 2.1
    Mars exploration.

    Objective 2.2
    Outer Solar System exploration

    Objective 3.1
    Sources of prebiotic materials and catalysts

    Objective 3.2
    Origins and evolution of functional biomolecules