Active Interrogation of Analog Planetary Surfaces using Neutron and Gamma-Ray Instruments
Abstract
Gamma-ray and neutron spectrometers (GRNS) can be used to determine the hydrogen content and elemental abundances within the top several tens of centimeters of planetary surfaces. Through the use of a DT (Deuterium-Tritium) pulsed neutron generator (PNG) GRNS can more rapidly characterize a planet's outermost crustal layer. This makes active GRNS useful for roving and landed missions. The first planetary active neutron investigation, the Dynamic Albedo of Neutrons is returning significant scientific results from the surface of Mars (e.g. depth of hydrogen and silicate fracture halos, amongst others). The recently selected Dragonfly mission to Saturn's Titan will also carry an active GRNS. In addition, several other active neutron and gamma-ray instruments are in development. Active GRNS measurements were performed - at the NASA Goddard Space Flight Center Goddard Geophysical and Astronomical Observatory outdoor test site - to interrogate geologically relevant materials (Mars, the Moon, Titan). Several GRNS instruments (CLYC, HPGe, CeBr) were characterized for use with both passive and active techniques to simulate deployment on a rover or lander. By running the neutron generator in a pulsed mode (250 - 1000 Hz), we were able to study GRNS detector responses during and between pulses, as well as delayed responses after the generator was turned off. We successfully acquired neutron die-away curves, sensitive to bulk hydrogen abundance, compositional layering and neutron absorption, as well as gamma-ray spectra, sensitive to Fe, Si, Al, O, K, Th abundances. We investigated analog materials relevant to planetary science missions such as basalt (volcanic, extrusive), granite (crustal, intrusive, high Th & K), fertilizer (organics), iron blocks (core of a differentiated planetesimal), and polyethylene (water ice, hydrated minerals, and organics) for our measurements. These experiments contribute to a better understanding of instruments that will be useful for future landed missions to Mars, the Moon, Titan, and other planetary bodies.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMEP53F2244H
- Keywords:
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- 1813 Eco-hydrology;
- HYDROLOGY;
- 1824 Geomorphology: general;
- HYDROLOGY;
- 1825 Geomorphology: fluvial;
- HYDROLOGY;
- 1826 Geomorphology: hillslope;
- HYDROLOGY