Solar storm sparks global aurora, doubles radiation levels on Mars
An unexpectedly strong solar storm proved once again that the Sun, our closest star, is a remarkably powerful orb that exerts a huge influence over the bodies within the Solar System.
Last month’s increased solar activity came as a surprise to scientists as it occurred during the period of minimal activity in the Sun’s 11-year sunspot and solar-storm cycle. By all accounts, the Sun should be reaching its minimum activity level; instead, the solar storm, which peaked on September 11, 2017, produced a huge coronal mass ejection (CME), the likes of which haven’t been seen in more than 12 years, and the eighth largest since modern solar activity records began in 1996.
Sonal Jain of the University of Colorado Boulder’s Laboratory for Atmospheric and Space Physics, who is a member of NASA’s Mars Atmosphere and Volatile EvolutioN (MAVEN) mission’s Imaging Ultraviolet Spectrograph instrument team, said: “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.”
The impact of the storm was detected on Mars more than 140 million miles (228 million kilometers) away from the Sun. Multiple instruments in orbit and on the surface of Mars detected the event. MAVEN detected giant global auroras that encircled Mars for more than two days. The auroras created by the storm were twenty-five times brighter than anything previously seen by MAVEN since its arrival in Martian orbit in 2014.
On the Red Planet itself, the Radiation Assessment Detector (RAD) aboard the Curiosity rover, part of NASA’s Mars Science Laboratory (MSL), also detected the event. The RAD recorded radiation levels on the surface of the planet greater than twice what the highest previous radiation levels that the instrument had registered since Curiosity’s August 2012 landing on Mars. The increased radiation levels during the event lasted for more than two days.
Throughout MSL’s interplanetary spaceflight, from November 2011 to August 2012, Curiosity’s RAD monitored radiation levels inside spacecraft capsule in which the rover resided; the device has been regularly observing the radiation environment on the surface of Mars for more than five years.
MAVEN and Curiosity weren’t the only missions to detect the spike in activity. The Mars Odyssey, Mars Reconnaissance Orbiter, as well as the European Space Agency’s Mars Express spacecraft observed the storm around Mars.
“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 in Washington, D.C.
Understanding the impact of solar activity is crucial in the preparation for any human crewed missions that we may want to send to Mars, as well as for understanding the habitability when it comes to the search for life – whether current or in the past – at the fourth planet from the Sun. This kind of solar activity produces additional secondary particles that not only need to be monitored and better understood but also shielded against.
“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 spacewalk outside the International Space Station,” said RAD Principal Investigator Don Hassler of the Southwest Research Institute in Boulder, Colorado. “To protect our astronauts on Mars in the future, we need to continue to provide this type of space weather monitoring there.”
This event has shown clearly that increased solar activity has an intensely greater increase to radiation that penetrates through Mars’ atmosphere and down to the Mars’ surface.
LEFT: Energetic particles from a large solar storm in September 2017 were seen both in Mars orbit by NASA’s MAVEN orbiter, and on the surface of Mars by NASA’s Curiosity Mars rover. Image & Caption Credit: NASA / GSFC / JPL-Caltech / Univ. of Colorado / SwRI-Boulder / UC Berkeley. RIGHT: These profiles show the brightness of auroras in Mars’ atmosphere at different altitudes. The solid black profile on the right is from a September 2017 solar storm. Barely visible along the vertical axis is a dashed profile from the previous brightest aurora seen by MAVEN, in March 2015. Image & Caption Credit: NASA / GSFC / Univ. of Colorado
“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 Hassler. “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.”
Jain said: “When a solar storm hits the Martian atmosphere, it can trigger auroras that light up the whole planet in ultraviolet light. The recent one lit up Mars like a light bulb. An aurora on Mars can envelop 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.”
Analysis of the data is just beginning; however, MAVEN’s Principal Investigator Bruce Jakosky, of the University of Colorado Boulder, said: “We expect to get a better understanding of how the process operates in the upper atmosphere of Mars today, and [gain] a better understanding of how storms like this may have stripped away much of the Martian atmosphere in the past.”
It is thought that the loss of most of Mars’ original atmosphere to space may be linked to the planet’s change from a wet and warmer to a dry and colder planet several billion years ago.
The solar event that lit up Mars’ upper atmosphere was massive enough to also impact Earth far on the other side of the Sun from Mars. Thankfully, unlike Mars, Earth is protected by a strong magnetosphere. Even so, for several days, the Earth experienced intense auroras as far south as Oregon, Idaho, and Ohio, and HAM radio operators who were assisting with hurricane communications for Harvey and Irma also experienced problems with signal interference due to the massive solar activity.
A native of the Greater Los Angeles area, Ocean McIntyre's writing is focused primarily on science (STEM and STEAM) education and public outreach. McIntyre is a NASA/JPL Solar System Ambassador as well as holding memberships with The Planetary Society, Los Angeles Astronomical Society, and is a founding member of SafePlaceForSpace.org. McIntyre is currently studying astrophysics and planetary science with additional interests in astrobiology, cosmology and directed energy propulsion technology. With SpaceFlight Insider seeking to expand the amount of science articles it produces, McIntyre was a welcomed addition to our growing team.