Variability in low Mars atmosphere's H$_2$O concentration stimulated by solar cycle activity

TL;DR

This study investigates the link between solar cycle activity and water vapor variability in Mars' atmosphere, using spectral analysis of observational data to identify periodic oscillations related to solar flux changes.

Contribution

It introduces the Lomb-Scargle Periodogram as a heuristic tool for analyzing oscillatory activity in planetary atmospheres with uneven data sampling, validated through Earth's atmospheric models.

Findings

Detected periodic oscillations in Mars' H$_2$O vapor linked to the solar cycle.

Validated the spectral analysis method using Earth's atmospheric chemical data.

Proposed a new approach for studying planetary atmospheric variability.

Abstract

Mars' thin, CO$_2$-rich atmosphere poses a unique puzzle involving composition, climate history, and habitability. This work explores the intrincate relationship between Mars' atmospheric variations and dynamic solar activity patterns. We focus on periodic oscillations in H$_2$O vapor and the Pectinton solar flux index in the $\lambda$ = 10.7 cm radio band, around the characteristic 11-year solar cycle. Periodic Mars activity was studied using data from Mars Express' SPICAM instrument spanning 2004-2018. The Lomb-Scargle Periodogram method was applied to analyze the power spectra of both signals around this period, calibrated using peaks associated with the seasonal Martian cycle. This method was validated by analyzing power spectra of chemical species abundances in Earth's atmosphere, obtained from the NRLMSISE 00 empirical model provided by the National Oceanic and Atmospheric Administration (NOAA). Model executions reproduced chemical abundance data for various atmospheric species (N$_2$, O$_2$, N, H$_2$, Ar, and He) at two reference heights (upper mesosphere and low ionosphere) over a 1961-2021 time span. Results suggest a connection between variability in H$_2$O vapor concentration in Mars' atmosphere and fluctuations in the Pectinton solar flux index. We propose the Lomb-Scargle Periodogram method as a heuristic for studying oscillatory activity in planetary atmospheres with non-uniformly sampled data. While our results provide valuable insights, further analysis, cross-referencing with data from different orbiters, is required to deepen our understanding of these findings in the fields of planetary climatology and atmospheric physics.