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Large Solar Storm Sparks Global Aurora, Doubles Radiation Levels at Mars

For immediate release

San Antonio — An unexpectedly strong blast from the Sun hit Mars this month and was observed by NASA missions in orbit and on the surface. The Mars Science Laboratory’s Radiation Assessment Detector, led by Southwest Research Institute (SwRI), and the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft, led by the University of Colorado Boulder, both detected unparalleled effects at the Red Planet.

“NASA’s distributed set of science missions is in the right place to detect activity on the Sun and examine the effects of such solar events at Mars as never possible before,” said MAVEN Program Scientist Elsayed Talaat, program scientist at NASA Headquarters, Washington, for MAVEN.

The solar event on Sept. 11, 2017, sparked a global aurora at Mars more than 25 times brighter than any previously seen by the MAVEN orbiter, which has been studying the Martian atmosphere’s interaction with the solar wind since 2014.

It also produced radiation levels on the surface more than double any previously measured by the Curiosity rover’s Radiation Assessment Detector, or RAD, since that mission’s landing in 2012. The high readings lasted more than two days.

“When a solar storm hits the Martian atmosphere, it can trigger auroras that light up the whole planet in ultraviolet light,” said Sonal Jain of the University of Colorado Boulder Laboratory for Atmospheric and Space Physics, who is a member of MAVEN's Imaging Ultraviolet Spectrograph instrument team. “The recent one lit up Mars like a light bulb.”

Strangely, it 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. This event was big enough to be detected at Earth too, even though Earth 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,” said Jain.

“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 RAD Principal Investigator Don Hassler of SwRI. “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.”

RAD monitored radiation levels inside the encapsulated spacecraft that carried Curiosity from Earth to Mars in 2011 and 2012 and has been steadily monitoring the radiation environment at Mars’ surface for more than five years.

RAD findings strengthen understanding of radiation’s impact on Mars habitability, a key objective of the Curiosity mission. NASA is also using RAD findings for planning the safety of human-crew missions to Mars. Highly energetic solar events can significantly increase the radiation that penetrates through the atmosphere to the Mars surface. The increased radiation also interacts with the atmosphere to produce additional, secondary particles, which need to be understood and shielded against to ensure the safety of future human explorers.

“If you were outdoors on a Mars walk and learned that an event like this was imminent, you would definitely want to take shelter, just as you would if you were on a space walk outside the International Space Station,” Hassler said. “To protect our astronauts on Mars in the future, we need to continue to provide this type of space weather monitoring there.”

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 this month’s event, are broad enough in extent to affect planets in quite different directions from the Sun.

“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,” Jain said. “The energetic particles from the Sun also can be absorbed by the upper atmosphere, increasing its temperature and causing it to swell up.”

Analysis of the data is just beginning. “We expect to get a better understanding of how the process operates in the upper atmosphere of Mars today, and a better understanding of how storms like this may have stripped away much of the Martian atmosphere in the past,” said MAVEN Principal Investigator Bruce Jakosky of the University of Colorado Boulder. The loss of most of Mars’ original atmosphere to space is linked to the planet’s change from wet to dry, long ago.

Besides the observations by instruments on MAVEN and Curiosity, effects of the Sept. 11, 2017, event were also detected by instruments on NASA’s Mars Odyssey orbiter and Mars Reconnaissance Orbiter and by the European Space Agency’s Mars Express orbiter.

NASA’s Goddard Space Flight Center, Greenbelt, Maryland, manages the MAVEN mission for the principal investigator at the University of Colorado. NASA’s Jet Propulsion Laboratory, Pasadena, California, manages the Curiosity mission for NASA’s Science Mission Directorate, Washington. RAD is supported by NASA’s Human Exploration and Operations Mission Directorate, Washington, under JPL subcontract to Southwest Research Institute, San Antonio, and by Germany’s national space agency (DLR) under contract with Christian-Albrechts-Universitat, Kiel, Germany.

For more information, contact Deb Schmid, (210) 522-2254, Communications Department, Southwest Research Institute, PO Drawer 28510, San Antonio, TX 78228-0510.

Media Resources

Media Title: 
Maven Mars images
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MAVEN images show the sudden appearance of a bright aurora on Mars during a solar storm in September 2017
These MAVEN 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 ultraviolet light seen on Mars' night side before (left) and during (right) the event. SwRI’s Radiation Assessment Detector confirmed the data on the surface from aboard NASA’s Curiosity rover.
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Image courtesy of NASA/Univ. of Colorado
Media Title: 
Mars radiation dose rate
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Radiation Assessment Monitor chart shows a spike in the radiation dose on the Martian surface
During a massive solar storm in September, SwRI’s Radiation Assessment Monitor instrument on NASA’s Curiosity rover measured a spike in the radiation dose on the Martian surface. Surface radiation more than doubled, reaching almost 600 micrograys, which measure absorbed radiation dosage.
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Image courtesy of NASA/JPL-Caltech/Univ. of Colorado/SwRI-Boulder/UC Berkeley