Maize (Zea mays L.) survival on Mars depends on regolith's chemical composition rather than reduced gravity or lack of magnetic field

The long-term success of human missions to Mars requires the ability of plants, like maize (Zea mays L.), to thrive under Martian conditions. We assessed the combined effects of the planet’s unique biophysical environment by simulating Martian gravity (sMG, 0.38 g) and Mars hypomagnetic field (hMF, ~ 40 nT) and the chemical toxicity of Mars Global Simulant (MGS-1) regolith. We conducted comprehensive mineralogical characterization of MGS-1 using PXRD, SEM-EDXS, and S/TEM-EDXS. Maize was cultivated in a 30% MGS-1 substrate under sMG and hMF conditions. Analyses included morphological assessments, biochemical measurements, and gene expression. MGS-1 characterization revealed mineral phases (e.g., quartz, mica), enhancing its chemical complexity. Applied alone, hMF and sMG triggered specific compensatory responses in auxin transport and metabolism (e.g., sMG increased leaf area; hMF modulated protein content). In dual-stress scenarios, MGS-1 emerged as the dominant stressor, overriding biophysical cues. The hMF + MGS-1 combination enabled metabolic retention (elevated protein and root PIN plasticity), indicating manageable stress. Conversely, sMG + MGS-1 posed the greatest threat, inducing systemic metabolic depletion (decreased protein and proline) and disrupting root development signals (PIN downregulation). Ultimately, maize survival on Mars is primarily constrained by regolith chemical imbalance and toxicity, rather than reduced gravity or hypomagnetism alone.