The Role of Crustal Magnetic Fields In Atmospheric Escape From Mars

Weber, Tristan

Graduate Thesis Or Dissertation

The Role of Crustal Magnetic Fields In Atmospheric Escape From Mars Public Deposited

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Citations

Citeable URL: https://scholar.colorado.edu/concern/graduate_thesis_or_dissertations/1544bq39m

Abstract

Magnetic fields may have played an important role in shaping the planetary evolution of Mars. Through their ability to guide the flow of charged particles, magnetic fields facilitate both the input of energy and the escape of planetary ions, which at Mars has contributed to the loss of the planet's atmosphere over time. This atmospheric loss has been a primary driver of Martian evolution, altering the planet from one that sustained flows of liquid water to the cold, dry world we observe today.

In this thesis, I use data from the MAVEN spacecraft to characterize the magnetic field environment of Mars, placing a particular emphasis on how Martian crustal magnetic fields affect atmospheric escape.

Through measurements of electron pitch angle distributions and magnetic fields, I analyze magnetic topology throughout the Martian system, allowing us to determine where magnetic fields are providing avenues for energy input and ion escape at Mars. This work was then used as a foundation for the creation of a new technique for identifying magnetic topology at Mars.

I then perform studies of how Martian magnetic topology responds to changes in upstream solar wind conditions, namely solar wind pressure and interplanetary magnetic field direction. Solar wind conditions are expected to have been drastically different throughout solar system history, so an understanding of how magnetic fields at Mars respond to these conditions is needed in the context of interpreting long term evolution. I find that changes in solar wind pressure alter the morphology of crustal magnetic field structures, and that changes in upstream IMF cause local variations in topology on consistent, daily timescale.

Finally, I couple the previous works with direct measurements of escaping ions to estimate the influence that crustal magnetic fields have on atmospheric escape. I find that crustal fields typically inhibit ion escape from Mars, but that under certain conditions they can instead cause localized enhancements in escape. Comparisons with modeling results in the future may help determine precisely what conditions are necessary for this to occur.

Analysis of the Martian crustal magnetic fields may act as a gateway toward understanding the importance of planetary magnetic fields in general. As we begin to study more and more worlds throughout the universe, the work of this thesis could represent a small step toward characterizing the habitability of planets in general.

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