Brilliant Martian aurora sheds light on Mars’ changing climate

This story was adapted from a version originally published by NASA’s Goddard Space Flight Center. Read the original version here.

A type of Martian aurora first identified by NASA’s MAVEN spacecraft in 2016 is actually the most common form of aurora occurring on the Red Planet, according to new results from the mission. The aurora is known as a proton aurora and can help scientists track water loss from Mars’ atmosphere.

MAVEN images of the Martian atmosphere under normal conditions (left) and with an aurora (middle and right). (Credit: Embry-Riddle Aeronautical University/LASP, CU Boulder)

Andréa Hughes of Embry-Riddle Aeronautical University in Florida led the research, which also included scientists from the Laboratory for Atmospheric and Space Physics (LASP) at CU Boulder. The team presented its results Dec. 12 at the American Geophysical Union meeting in San Francisco.

At Earth, aurora are commonly seen as colorful displays of light in the night sky near the polar regions, where they are also known as the northern and southern lights. However, the proton aurora on Mars happen during the day and give off ultraviolet light, so it is invisible to the human eye but detectable to the Imaging UltraViolet Spectrograph (IUVS) instrument on the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft.

“At first, we believed that these events were rather rare because we weren’t looking at the right times and places,” said Mike Chaffin, research scientist at CU Boulder’s LASP and a coauthor of the study. “But after a closer look, we found that proton aurora are occurring far more often in dayside southern summer observations than we initially expected.”

Conceptual image depicting the early Martian environment (right) – believed to contain liquid water and a thicker atmosphere – versus the cold, dry environment seen at Mars today (left). Credits: NASA’s Goddard Space Flight Center

MAVEN’s mission is to investigate how the Red Planet lost much of its atmosphere and water, transforming its climate from one that might have supported life to one that is cold, dry, and inhospitable. Since the proton aurora is generated indirectly by hydrogen derived from Martian water that’s in the process of being lost to space, this aurora could be used to help track ongoing Martian water loss.

“In this new study using MAVEN/IUVS data from multiple Mars years, the team has found that periods of increased atmospheric escape correspond with increases in proton aurora occurrence and intensity,” Hughes said. “Perhaps one day, when interplanetary travel becomes commonplace, travelers arriving at Mars during southern summer will have front-row seats to observe Martian proton aurora majestically dancing across the dayside of the planet (while wearing ultraviolet-sensitive goggles, of course).”

MAVEN researchers have also reported on the existence of discrete and diffuse aurora on Mars, which occur on the planet’s nightside.

The team has found proton aurora in about 14% of their dayside observations, which increases to more than 80% of the time when only dayside southern summer observations are considered. “By comparison, IUVS has detected diffuse aurora on Mars in a few percent of orbits with favorable geometry, and discrete aurora detections are rarer still in the dataset,” said Nick Schneider, a coauthor of the new study and lead of the IUVS team at LASP.

Credits: NASA/MAVEN/Goddard Space Flight Center/Dan Gallagher

Proton aurora form when solar wind protons (which are hydrogen atoms stripped of their lone electrons by intense heat) interact with the upper atmosphere on the dayside of Mars.

As they approach Mars, the protons coming in with the solar wind transform into neutral atoms by stealing electrons from hydrogen atoms in the outer edge of the Martian hydrogen corona, a huge cloud of hydrogen surrounding the planet. When those high-speed incoming atoms hit the atmosphere, some of their energy is emitted as ultraviolet light.

This research was funded by the MAVEN mission. MAVEN’s principal investigator is based at LASP, and NASA Goddard manages the MAVEN project. NASA is exploring our Solar System and beyond, uncovering worlds, stars, and cosmic mysteries near and far with our powerful fleet of space and ground-based missions.

This story was written by Daniel Strain and originally appeared in CU Boulder Today.