A solar event on September 11, 2017 sparked a global aurora on the Red Planet more than 25 times brighter than any previously seen by NASA’s MAVEN (Mars Atmosphere and Volatile Evolution) spacecraft. The event also produced radiation levels on the Martian surface more than double any previously measured by NASA’s Curiosity rover.
The Sun is always emitting a continuous stream of charged particles, mainly electrons and protons.
Occasionally, eruptions called coronal mass ejections occur, with higher density, energy and speed of the ejected particles.
These events vary in strength. Strong ones cause dramatic aurora displays on Earth, and very strong ones can disrupt communications. Some coronal mass ejections, such as the September 11 event, are broad enough in extent to affect planets in quite different directions from the Sun.
“When a solar storm hits the Martian atmosphere, it can trigger auroras that light up the whole planet in UV light. The recent one lit up Mars like a light bulb,” said Dr. Sonal Jain, a member of MAVEN’s Imaging Ultraviolet Spectrograph instrument team and a researcher at the University of Colorado Boulder’s Laboratory for Atmospheric and Space Physics.
“An aurora on Mars can envelope the entire planet because Mars has no strong magnetic field like Earth’s to concentrate the aurora near polar regions.”
“The energetic particles from the Sun also can be absorbed by the upper atmosphere, increasing its temperature and causing it to swell up.”
These images show the sudden appearance of a bright aurora on Mars during a solar storm in September 2017. The purple-white color scheme shows the intensity of UV light seen on Mars’ night side before (left) and during (right) the event. A simulated image of Mars for the same time and orientation has been added, with the dayside crescent visible on the right. The auroral emission appears brightest at the edges of the planet where the line of sight passes along the length of the glowing atmosphere layer. The data are from observations by the Imaging Ultraviolet Spectrograph instrument (IUVS) on NASA’s MAVEN orbiter. Note that, unlike auroras on Earth, the Martian aurora is not concentrated at the planet’s polar regions. This is because Mars has no strong magnetic field like Earth’s to concentrate the aurora near the poles. Image credit: NASA / University of Colorado.
Strangely, the September 11 event occurred in conjunction with a spate of solar activity during what is usually a quiet period in the Sun’s 11-year sunspot and storm-activity cycle.
The event was big enough to be detected at Earth too, even though our planet was on the opposite side of the Sun from Mars.
“The current solar cycle has been an odd one, with less activity than usual during the peak, and now we have this large event as we’re approaching solar minimum,” Dr. Jain said.
“This is exactly the type of event both missions were designed to study, and it’s the biggest we’ve seen on the surface so far,” said Dr. Don Hassler, a researcher at the Southwest Research Institute and the principal investigator for Curiosity’s Radiation Assessment Detector.
“It will improve our understanding of how such solar events affect the Martian environment, from the top of the atmosphere all the way down to the surface.”
Source: Sci News
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