Mars has auroras, but they do not behave like the ones on Earth. NASA's MAVEN spacecraft has found that the Red Planet hosts two distinct types of these light shows, and neither one is driven by a global magnetic field the way Earth's northern and southern lights are.
A proton aurora that glows every day
The first type is called a proton aurora. On Earth, proton auroras are rare and faint. On Mars, they happen constantly. MAVEN data show that during the day, a steady stream of protons from the Sun slams into the hydrogen gas surrounding Mars. This collision produces ultraviolet light. The glow is invisible to the human eye but detectable by instruments on the spacecraft. It appears on the dayside of the planet, not at the poles.
A second aurora that reaches deep into the atmosphere
The second type is a diffuse aurora. It appears when solar storms send a burst of energetic particles toward Mars. Because Mars lacks a global magnetic field, those particles can travel straight down into the atmosphere, reaching altitudes as low as 60 kilometers. On Earth, the magnetic field deflects most of those particles away from the surface. On Mars, the particles hit the air directly and create a widespread, faint glow across the entire planet.
MAVEN has been orbiting Mars since 2014. The mission is run by NASA from the United States. Its goal is to study how the Martian atmosphere escapes into space. The discovery of these two aurora types came from analyzing data collected over several years. Scientists at the University of Colorado Boulder and other institutions worked on the findings.
Local interest on Mars is obviously nonexistent, but for planetary scientists, the auroras matter because they reveal how the Sun interacts with the Martian atmosphere. The proton aurora shows that hydrogen gas is present high above the planet. The diffuse aurora shows that solar particles can penetrate deeper than expected. Both processes affect how the atmosphere erodes over time.
These auroras are not just pretty lights. They are evidence of the forces that have stripped away much of Mars' atmosphere over billions of years. Understanding them helps scientists piece together why Mars changed from a warm, wet world into the cold desert it is today.
