The Solar Energetic Particle experiment on MAVEN: first results

The Solar Energetic Particle (SEP) instrument arrived at Mars onboard the Mars Atmosphere and Volatile EvolutioN (MAVEN) Mission on September 22, 2014. In order for MAVEN to determine the role that loss of volatiles to space has played through time, solar energy input to the Martian system must be characterized. An important (if infrequent and episodic) portion of this input is in the form of solar energetic particle (SEP) events. Understanding the relationship between SEP events and atmospheric escape is crucial to understanding the climate history of Mars. The SEP instrument characterizes such events at Mars by measuring energetic protons and electrons in the energy range absorbed by the upper atmosphere. Additionally, under certain conditions, SEP directly measures the flux of escaping Oxygen that has been picked up by the Solar Wind and can provide limits on this important escape mechanism. The implications of the model comparison with SEP data for the escape of neutral oxygen from Mars will be discussed. SEP takes much of its heritage from the Solid State Telescope (SST) on the THEMIS mission, consisting of 2 orthogonal dual double-ended solid-state telescopes. Proton spectra from 25 keV to 6 MeV and electron spectra from 25 keV to 1 MeV will be collected in 4 look directions at 3 measurement cadences over MAVEN’s 4.5-hour elliptical orbit: 32s far from the planet, 8s between 300 and 800 km altitude and 2s below 300 km. SEP measures particle fluxes from ~20 to ~107 cm-2 s -1 sr-1. We will present results from the first 5 months of the MAVEN science mission.