Discipline: Technology and Engineering
Subcategory: Electrical Engineering
Alex Fournier - Norfolk State University
Co-Author(s): Aaron Savage, Min Kim, and Hargsoon Yoon, Norfolk State University, Norfolk, VA
Polycyclic aromatic hydrocarbons (PAH) are composed of hydrogen and carbon formed into repeating rings of C6H6, where the number of rings determine the molecule. PAH, such as Napthalene, Phenanthrene and Pyrene, are thought to be a possible fundamental precursor to life . If this is the case then it is reasonable to assume that if they can be found on the surface of Mars that two things are possible 1) there was and/or life on Mars, and 2) Mars could be made capable of sustaining human life. The question then become how to detect these PAH compounds on the surface of Mars. The current spectrometer used by the Mars Science Laboratory is a Laser-Induced Breakdown Spectrometer (LIBS) . This process uses a high powered laser to generate a plasma at the surface of the detection site then measures the light given off by the plasma . LIBS while effective is destructive, therefore it is proposed that, for measuring PAH, fluoro-spectroscopy would provide a simple, non-destructive alternative. Fluoro-spectroscopy uses a stimulation light source that excites the electrons in the molecules present and measures the photons emitted by the return of the electrons to a non-excited state. It is now known that PAH fluoresce at specific wavelengths depending on which PAH is present and the excitation wavelength [4,5,6], this makes a fluoro-spectrometer an ideal device to detect their presence. Napthalene and Phenanthene were chosen as target PAH because they are the two simplest PAH compounds comprising of 2 and 3 rings respectively. Through the use of a spectrophotometer it was determined that the intensity of the fluorescence of the target PAH peaked when excited in the ultra violet (UV) range. The requirements for a device to be employed on a Mars rover include compact, lightweight and energy efficient. Therefore the design of this Micro spectrometer consists of a single UV light emitting diode (LED) for excitation and a linear CCD array to capture the fluorescence spectrum after optical manipulation. The device was tested using pure samples of the compounds and various ratios of the pure samples and a 35 micron mica powder. The Mica powder was chosen as a soil analog because it is known that the Martian surface consists of a fine powder top soil over a solid rock base and because Mica would add any background fluorescence. In testing it was found that the device was capable of detecting the target PAH when pure and when combined with the soil analog. Other compounds tested were calcium carbonate and calcium sulfate as these are common elements of the Martian surface . These compounds were also detectable using the device. In order to increase spectral resolution and intensity of the fluorescence lenses and optics are currently being added to focus and collimate the excitation beam and to enhance the collection of the fluoresced photons.
Funder Acknowledgement(s): NSF-CREST
Faculty Advisor: Hargsoon Yoon, email@example.com
Role: My part of this research has been to develop testing procedure including target materials, conduct the testing and process the data.