Mars Aurora on the Rise to Solar Max

Mars’ lack of a global magnetic field led to initial low expectations for auroral phenomena on the planet. MAVEN observations showed auroral activity to be frequent, diverse in nature, and often global in scope. Subsequent observations by the Emirates Mars Mission further expanded the breadth of observable types of aurora, and variety will likely increase further. There are three fundamentally different types of aurora on Mars. Ironically, Mars’ lack of a global field is actually responsible for most of the activity, which leads to a new perspective for non-magnetized objects in our solar system and beyond.

This presentation will focus on aurora caused by solar energetic particles, the type of aurora most dependent on solar activity. MAVEN/IUVS discovered that the entire visible nightside of Mars can be engulfed in diffuse auroral emissions. Some diffuse aurora events have been observed to last for days during extended solar events. All auroral events are closely correlated with the arrival of SEP particles as measured by MAVEN’s SEP instrument.

SEP aurora events are currently occurring at the highest frequency of MAVEN’s 10 year mission. The phenomenon was discovered in 2014, and only two additional major events were observed in the following 7 years. Since August 2022, IUVS has observed 12 major events. The substantial dataset of recent events will be ideal for comparative studies to identify the particle types and energy ranges responsible, and see how Mars’ “hybrid magnetosphere” responds.

In additional to auroral science goals, our efforts aim to quantify how aurora can serve as a proxy for space weather hazard for human exploration of Mars. This leads to the ironic situation where the aurora may be so impressive it’s necessary to seek shelter against the radiation.

Visible wavelength emissions are predicted to accompany UV emissions from SEP aurora, based on atomic and molecular physics with known branching ratios. Oxygen green line emission is expected at 557 nm, as frequently seen at Earth. Brightnesses are expected to be detectable with visible wavelength cameras capable of long exposures, as well as detectable to the human eye.

Future Mars missions with instruments designed for nightside imaging offer tremendous low-cost potential for breakthrough observations in auroral science. Visible filter imaging of the aurora with conventional technology is likely to be orders of magnitude more sensitive than the complex and expensive slit-scanning spectral imagers in orbit at Mars today. The M-MATISSE mission, currently in a competitive Phase A Study for an ESA M-class mission, carries such a camera.