The M‑MATISSE mission: Exploring planetary space weather at Mars

The Mars Magnetosphere, ATmosphere, Ionosphere and Space‑weather SciencE (M‑MATISSE) mission is an ESA Medium‑class (M7) candidate. M‑MATISSE is designed to address one of the most outstanding challenges in Mars science: understanding how the solar wind and space‑weather drivers couple simultaneously to the Martian magnetosphere, ionosphere, thermosphere, and lower atmosphere, and how energy is transferred across these interconnected regions.The primary scientific objective of M‑MATISSE is to characterize the spatio‑temporal variability of the Martian Magnetosphere–Ionosphere–Thermosphere (M‑I‑T) system, its response to solar‑wind forcing, and the processes governing the dissipation of external energy at Mars. These couplings play a fundamental role in controlling atmospheric escape, auroral activity, radiation penetration, and the long‑term evolution of the Martian atmosphere and climate. In addition, quantifying the space weather and space‑climate environment at Mars is critical for future robotic and human exploration, as it enables improved forecasting of hazardous radiation and plasma conditions.M‑MATISSE addresses these objectives through three core science themes:(1) global characterization of M‑I‑T coupling via coordinated measurements of solar‑wind energy input and magnetosphere–ionosphere response;(2) determination of the radiation environment and the absorption, redistribution, and variability of energy within the M‑I‑T system; and(3) investigation of ionosphere–lower‑atmosphere coupling, an interface that remains poorly explored but is crucial for understanding solar energetic particle impacts and radio‑wave propagation at Mars.The mission concept consists of two coordinated orbiters carrying complementary, high‑heritage payloads. Together, they provide a multi‑point observational framework that combines in‑situ plasma measurements with remote sensing of the ionosphere and lower atmosphere, including radio cross‑link observations between spacecraft. This configuration enables simultaneous sampling of the upstream solar wind, the Martian plasma environment, and regions extending deep into the nightside magnetotail, an observational capability not previously achieved at Mars.Beyond planetary science, M‑MATISSE will provide the heliophysics community with a dedicated solar‑wind monitor at ~1.38-1.66 AU, offering valuable constraints on solar‑wind and solar‑transient propagation in the inner solar system. By linking solar disturbances from interplanetary space down to the Martian surface, M‑MATISSE represents the first mission fully dedicated to planetary space weather at Mars, with transformative implications for both fundamental science and future exploration.