Modeling the variations of Dose Rate measured by RAD during the first MSL Martian year: 2012-2014

TL;DR

This study analyzes RAD measurements on Mars from 2012-2014, revealing how atmospheric and solar variations influence surface radiation dose rates, enabling empirical predictions of Martian radiation conditions.

Contribution

The paper presents the first comprehensive empirical model linking Martian atmospheric pressure, solar activity, and radiation dose rates based on MSL RAD data.

Findings

Long-term seasonal and solar modulation effects significantly influence dose rates.

Empirical models can predict radiation dose under varying atmospheric and solar conditions.

Surface radiation environment estimates improve understanding of Martian habitability.

Abstract

The Radiation Assessment Detector (RAD), on board Mars Science Laboratory's (MSL) rover Curiosity, measures the {energy spectra} of both energetic charged and neutral particles along with the radiation dose rate at the surface of Mars. With these first-ever measurements on the Martian surface, RAD observed several effects influencing the galactic cosmic ray (GCR) induced surface radiation dose concurrently: [a] short-term diurnal variations of the Martian atmospheric pressure caused by daily thermal tides, [b] long-term seasonal pressure changes in the Martian atmosphere, and [c] the modulation of the primary GCR flux by the heliospheric magnetic field, which correlates with long-term solar activity and the rotation of the Sun. The RAD surface dose measurements, along with the surface pressure data and the solar modulation factor, are analysed and fitted to empirical models which quantitatively demonstrate} how the long-term influences ([b] and [c]) are related to the measured dose rates. {Correspondingly we can estimate dose rate and dose equivalents under different solar modulations and different atmospheric conditions, thus allowing empirical predictions of the Martian surface radiation environment.