MAVEN SEP Observations of Scorpius X‐1 X‐Rays at Mars: A Midatmosphere Occultation Analysis Technique

We report on the first observations of atmospheric occultations at Mars of ~10 keV X‐rays from an extrasolar source identified as Scorpius X‐1. The measurements are taken by the SEP (Solar Energetic Particle) instrument on the MAVEN (Mars Atmosphere and Volatile EvolutioN) spacecraft. The detected X‐ray photons from Scorpius X‐1 penetrate the Martian atmosphere down to ~70 km altitude, before being attenuated by the neutrals in the atmosphere. The occultation altitude varies by a few km depending on the source X‐ray energy and the atmospheric neutral density. In this work, we study the detection response of SEP to Scorpius X‐1 X‐rays and demonstrate that X‐ray occultation data can be used in conjunction with a model of the light extinction curve in order to gain insights into the neutral density of the Mars atmosphere in the 50–100 km altitude range, an important and largely unexplored altitude range at Mars. Key Points MAVEN/SEP at Mars detects 10–20 keV hard X‐rays from Scorpius X‐1, an extrasolar source ~9,000 light years away from the solar system The energy and field of view response of SEP to the measured X‐rays is studied and an X‐ray occultation case‐study is presented The X‐ray occultations can be used to gain insights into the neutral density of the Mars atmosphere in the 50–100 km altitude range