At Mars, the solar wind—a stream of charged particles from the Sun—interacts directly with the planet’s upper atmosphere, creating a sharp transition between the ionized atmosphere (ionosphere) and the shocked solar wind (magnetosheath). This boundary plays a key role in how Mars loses its atmosphere to space.

In this study, we use data from NASA’s MAVEN spacecraft to investigate how this transition region behaves. We analyze thousands of profiles of plasma density and magnetic field, focusing on a newly released, highly reliable dataset from MAVEN’s Langmuir Probe instrument. We identify the point where light solar wind ions and heavy planetary ions are equal in number—a marker for the center of the transition.

We then study how the shape and location of this density transition are influenced by physical forces, such as the pressure from the magnetic field and the thermal pressure of charged particles on both sides of the boundary. Our goal is to understand what controls the structure of this region and how it varies from orbit to orbit.

These insights help scientists better understand how the solar wind interacts with Mars and contributes to the ongoing loss of the Martian atmosphere.