2015 Annual Science Report

University of Wisconsin Reporting  |  JAN 2015 – DEC 2015

Project 1A: Ground Control Experiments for the OREOcube Mission

Project Summary

The OREOcube (ORganics Exposure in Orbit cube) experiment has been designed to study the effects of solar and cosmic radiation on astrobiology relevant organics when associated with mineral surfaces. The goal of this project is to investigate the (photo)chemical evolution and processing of organic matter in simulated proto-planetary and planetary microenvironments in the laboratory and in space. Testing the photostabitity and evolution of organics in actual space environments on the International Space Station (ISS) provides a powerful tool to study the combined impact of several relevant parameters (e.g., ultraviolet and comic radiation, microgravity) simultaneously. The OREOcube capability to measure in-situ changes of samples exposed to space radiation using an UV-visible-NIR spectrometer as a function of time in Low Earth Orbit will confer significant advantages relative to more basic ISS exposure facilities for which sample measurements are made on Earth prior to and at the end of a space mission. The innovative aspect of this OREOcube experiments is the capability of in-situ monitoring of flight samples, which has not yet been achieved on the ISS. A comparison of measurements performed with OREOcube with recent LEO data (EXPOSE-E, EXPOSE-R, O/OREOS Sat) and ground-based laboratory data will reveal how those combined data from different exposure facilities can be effectively used to investigate the evolution of organic matter in space.

4 Institutions
3 Teams
5 Publications
0 Field Sites
Field Sites

Project Progress

In collaboration with NASA Ames Research Center, Leiden University, and the SETI Institute, pre-flight experiments using sets of astrobiologically important organic samples in combination with mineral substrates have been performed under conditions that simulate anticipated conditions on an International Space Station external platform. In an OREOcube experiment, an adsorbate interface is defined by depositing organic samples as thin films onto solid substrates. Samples are housed in hermetically sealed reaction cells containing an internal test environment that allows control of headspace gases including the partial pressure of water vapor, see Figure 1. This provides a controlled method to examine organic samples and inorganic surface interactions.

Figure 1. OREOcube: Two independent 10-cm cubes each containing a 24-sample cell carrier and an integrated UV/Vis/NIR spectrometer are used to measure changes in in organic compounds exposed to low-Earth-orbit radiation conditions.

Tested inorganic substrates include hematite, magnetite, chromium oxide, titanium dioxide, nickel oxide, silica and alumina in combination with four classes of organics, polycyclic aromatic hydrocarbon (PAH), amino acid, metalloporphyrin, and quinone. The gathered data will allow us to select the most suitable and scientifically relevant organic-inorganic thin films combinations to be exposed on the ISS. Pre-flight ground-based research on the photochemistry of anthrarufin and iron tetraphenylporphyrin show that these compounds interact strongly with iron oxides in terms of electronic structure resulting in altered spectral features and overall absorptivity relative to other inorganic substrates, see Figure 2.

Figure 2. UV-visible spectral changes of anthrarufin films on fused silica (orange triangles) and with iron oxide (magnetite: green circles, hematite: blue squares) underlying films represented by relative changes in peak area compared to initial area of the anthrarufin main peak near 300 nm as a function of simulated solar exposure time. Small filled symbols represent two independent samples of a given type; open symbols are mean values of those two samples. Averaged data are least-squares fit to a model that accounts for a steady-state photolysis rate whenever the samples are illuminated, plus a step change in absorbance each time the samples are exposed (transiently) to air. Solid straight lines represent calculated changes in percentage peak area derived from the first term of the model which takes into account only the linear-with-time steady-state photolysis reaction and not the observed step degradation caused by each air exposure.
Figure 2. UV-visible spectral changes of anthrarufin films on fused silica (orange triangles) and with iron oxide (magnetite: green circles, hematite: blue squares) underlying films represented by relative changes in peak area compared to initial area of the anthrarufin main peak near 300 nm as a function of simulated solar exposure time. Small filled symbols represent two independent samples of a given type; open symbols are mean values of those two samples. Averaged data are least-squares fit to a model that accounts for a steady-state photolysis rate whenever the samples are illuminated, plus a step change in absorbance each time the samples are exposed (transiently) to air. Solid straight lines represent calculated changes in percentage peak area derived from the first term of the model which takes into account only the linear-with-time steady-state photolysis reaction and not the observed step degradation caused by each air exposure.

Our experiments show that the photolytic degradation on iron oxides is slower compared to silica and other substrates, which may result in improved preservation potential for these compounds.