Rula Tawalbeh

An AOTF-LDTOF spectrometer suite for in situ organic detection and characterization

We discuss the development of a miniature near-infrared point spectrometer, operating in the 1.7–4 mm region, based on acousto-optic tunable filter (AOTF) technology. This instrument may be used to screen and corroborate analyses of samples containing organic biomarkers or mineralogical signatures suggestive of extant or extinct organic material collected in situ from planetary surfaces. The AOTF point spectrometer will be paired with a laser desorption time-of-flight (LDTOF) mass spectrometer and will prescreen samples for evidence of volatile or refractory organics before the laser desorption step and subsequent mass spectrometer measurement. 1 2 We describe the prototype AOTF point spectrometer instrument and present laboratory analysis of geological samples of known astrobiological importance. An initial mineral and rock sample suite of planetary relevance was used in the laboratory for baseline testing. To this, we will add a complement of astrobiologically relevant biosignatures from a variety of well-characterized geomicrobial study sites. We also describe LDTOF analysis of kaolinite and serpentine specimens, which are both highly relevant to the Martian surface mineralogy and the aqueous history of the planet. The AOTF-LDTOF instrument pairing offers the powerful advantage of cross-checked chemical analyses of individual samples, which can reduce chemical and biological interpretation ambiguities.

Rapid assessment of high value samples: An AOTF-LDTOF spectrometer suite for planetary surfaces

We discuss the development of a miniature near-infrared point spectrometer, operating between 1.7-3.45 μm, based on acousto-optic tunable filter (AOTF) technology. This instrument may be used to screen and corroborate analyses of samples containing organic biomarkers or mineralogical signatures suggestive of extant or extinct organic material collected in situ from planetary surfaces. The AOTF point spectrometer will be paired with a laser desorption time-of-flight (LDTOF) mass spectrometer and will prescreen samples for evidence of volatile or refractory organics before the laser desorption step and subsequent mass spectrometer measurement. We describe the AOTF point spectrometer instrument and present laboratory analysis of geological samples of known astrobiological importance. We also present LDTOF spectra of the same samples analyzed with the AOTF, which highlights the value of a comparative data set with the two instruments. We discuss plans for the integration of the two instruments, which is scheduled to take place in the first half of 2012. The AOTF-LDTOF instrument pairing offers the powerful advantage of cross-checked chemical analyses of individual samples, which can reduce chemical and biological interpretation ambiguities.

Infrared acousto-optic tunable filter point spectrometer for detection of organics on mineral surfaces

Abstract. A prototype infrared (IR) acousto-optic tunable filter (AOTF)-based point spectrometer has been designed for examining and analyzing potential biological samples collected in situ from the planets or other solar system objects. The reflectance spectrometer operates at a wavelength range of 1.6 to 3.6 μm, which is diagnostic of minerals and organics, and inspects a 1-mm sized spot on the sample. The tuning component is the AOTF that has been utilized in a variety of spectral detection applications. The instrument’s specification and design approach including the selected components is described. The data acquisition system, the electronic components, and their interconnections are presented. The instrument’s radiometric performance is examined and described by a noise equivalent reflectance value of 0.13% that is obtained from the laboratory measurements. The device has been demonstrated by measuring the reflectance spectra for a variety of geological samples and comparing the results with the United States Geological Survey data.

Results from an integrated AOTF-LDTOF spectrometer suite for planetary surfaces

On future landed missions to Mars and small solar system bodies, efficient sample prescreening will be necessary to select interesting targets for further analysis by analytical instruments with very limited time and power resources. Near infrared spectroscopy is well suited for rapid and non-invasive identification of mineral classes, and for determining the possible presence of organic molecules. Here we describe a miniature acousto-optic tunable filter (AOTF) point spectrometer that is tunable from ~1.6 - 3.6 μm. It identifies minerals associated with aqueous environments at sample scales of ~1 mm, as well as organic molecules and volatiles. The AOTF point spectrometer was integrated with a laser desorption time-of-flight (LDTOF) mass spectrometer developed at NASAs Goddard Space Flight Center, and can be used to prescreen samples for evidence of organics before the laser desorption step and subsequent mass spectrometer measurement. The LDTOF mass spectrometer provides pulsed-laser desorption and analysis of refractory organic compounds up to 150,000 Da on a spatial scale of 50-100 μm, determined by the laser spot size at the target. The recent integration of the two instruments allowed for coincident spectral measurements of geologic samples; follow-up measurements from the LDTOF were taken from an identical region on the samples of interest, allowing for a direct comparison between the two complementary data sets. We present measurements of a standard sample suite consisting of sulfates, carbonates, clay minerals, and iron oxides. We also compare AOTF and LDTOF spectra of calcite, as well as gypsum doped with phthalic acid and valine, and discuss the relationship between reflectance spectra acquired by the AOTF and the LDTOF mass spectra. Finally, we discuss measurements made of irradiated ices such as those found in areas of high astrobiological interest like Europa.

Spectral mixture and chemometric algorithms applied to the identification of biosignatures on planetary surfaces

The utilization of a portable, low-mass, and low-power method for identifying biomarkers is essential for investigations of geologic samples on other terrestrial bodies, where spacecraft engineering requirements frequently constrain the mass and power consumption of scientific instruments. We discuss the capabilities and implementation of several in situ instruments with astrobiological applications to be used in possible future landed missions to other Solar System bodies. We present data collected from each instrument, discuss several analysis techniques, and discuss the unique results each instrument contributes to the identification of biosignatures.