Validated temporal gradient-driven gas migration on Earth as the primary mechanism for repeatable methane fluctuations on Mars.

 Validated temporal gradient-driven gas migration on Earth as the primary mechanism for repeatable methane fluctuations on Mars.

By

Hovav Zafrir¹, Yuval Reuveni², Ayelet Benkovitz², Zeev Zalevsky¹, Elad Levintal³, Noam Weisbrod³,Danielle Ilzycer⁴

 

¹ Faculty of Engineering, Bar Ilan University, Ramat-Gan 5290002, Israel

²Department of Physics, Ariel University, Ariel 4070000, Israel

³The Jacob Blaustein Institutes for Desert Research, BGU University, of the Negev, Sede Boker, Israel

⁴Soreq NRC, Yavne, Israel

 

ABSTRACT

A significant observation by Curiosity’s Tunable Laser Spectrometer in Mars' Gale Crater involves repeatable methane fluctuations with distinct seasonal and sub-diurnal variability. After a decade of data, these methane emissions clearly require robust geophysical explanations rooted in thermodynamics.

On Earth, extensive field and laboratory research have demonstrated that surface temperature gradients primarily drive subsurface gas flows, particularly those of Radon-222. This thermally induced transport exhibits an exponential dependence, verified through long-term field measurements (4 years (*)) and also in controlled laboratory conditions, where oscillating vertical gas flow closely matches surface heating cycles, from the natural one per day to one per eight days. The field monitoring has shown that radon gas flows downward throughout all daylight hours within the bedrock to a measured depth of 100 meters and responds inversely to atmospheric temperatures at night, creating an inverted surface temperature gradient that drives nocturnal exhalation.

While gases on Earth's ground also respond linearly to semi-diurnal barometric pressure changes (barometric pumping), within cracks, voids, or fractures between geological layers and structures, our experience indicates that such effects become negligible when the pressure gradient is less than 2 millibars. Specifically, on Mars, where barometric pressure is two orders of magnitude lower than Earth's, the resulting pressure gradient is insufficient to drive significant gas transport, even through sand on Earth's surface.

^(*) Benkovitz et al., 2023, https://doi.org/10.3390/rs15164094. Zafrir, et al., 2016, https://doi. org/10.1002/2016JB013033.