We used a pulsed 14 MeV neutron generator (NG) to acquire two concurrent gamma-ray spectra induced by inelastic neutron scattering (INS) and thermal neutron capture (TNC) in Si, O, and C, which are key elements in soil analyses. These separate spectra were acquired by gating the data acquisition system during the neutron pulse, to obtain an INS spectrum, and in between the neutron pulses, to obtain a TNC spectrum. Despite this separation, TNC gamma rays are still counted in the INS window due to the steady state achieved in the former reaction. With the NG operating at 10 kHz and a 25% duty cycle, the magnitude of the single-escape gamma rays from the Si 4.93 MeV gamma-ray peak in the TNC spectrum to the 4.43 MeV carbon region in the INS spectrum is 10.1% of the 4.93 MeV peak intensity. This percentage depends on the neutron repetition rate and duty cycle. It can be reduced to 4.9% by using a narrower gate-pulse that closely fits the neutron burst. We also show that under these conditions the net count rate in the individual peaks of soil elements, Si and O (6.13 MeV) of the TNC spectrum reaches a steady state between the neutron pulses, but the total count rate from the entire spectrum does not.
Life on Earth is characterized by a select group of low Z elements: C, H, N, O, P, K, S, Na, Cl. The presence of these elements and their ratios can provide indications of possible biogenicity and thus they may constitute valuable biomarkers that may help determine the best locations to seek more definitive evidence of life. We discuss the possible applications and significance of the inelastic neutron scattering induced gamma spectroscopy (INSGS) for future Astrobiology Missions to Mars or other solar System bodies. The general
requirements and capabilities of the proposed approach are presented.