While millions of earthlings were understandably obsessed with the prospect of a nuclear war erupting between the U.S. and North Korea, an unexpectedly strong blast from the Sun hit Mars this month. The effects were observed by NASA missions in orbit and on the surface, according to an American Astronomical Society News release. MAVEN Program Scientist Elsa Talaat, program scientist at NASA Headquarters, Washington, stated:
"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."
She was referencing a major solar event on Sept. 11, 2017 which 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 produced radiation levels on the surface more than double any previously measured by the Mars Curiosity Rover's Radiation Assessment Detector, or RAD, since that mission's landing in 2012. The high readings lasted more than two days. Needless to say, any 'MARS One' explorers left on that world would likely have experienced the brunt of the radiation and perished on the Red Planet.
Oddly, the solar storm affecting Mars occurred in conjunction with a spate of solar activity during what is usually a quiet period in the Sun's 11-year sunspot 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. According to Sonal Jain of the University of Colorado -Boulder's Laboratory for Atmospheric and Space Physics, who is a member of MAVEN's Imaging Ultraviolet Spectrograph instrument team:
"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,"
This is an anomaly I referenced some two years ago, in conjunction with disruptions of the solar tachocline and possible resulting disruptions of the meriodonal flow - affecting the alpha-omega torsional oscillations that give rise to the cycles of the (Babcock model) solar dynamo.. RAD Principal Investigator Don Hassler of the Southwest Research Institute's Boulder, Colorado, office, noted:
"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. 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."
The critical aspect, of course, is to trace such events to the energetic phenomena on the Sun and particularly the phenomenon of the solar 11- and 22-year cycles. (Which we believe are tied to the behavior of the solar dynamo.)
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. These 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. According to the SRI's Hassle:
"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. To protect our astronauts on Mars in the future, we need to continue to provide this type of space weather monitoring there."
This is an important point, and I hasten to note the Mars One project ballyhooed the past several years has not as yet incorporated any space weather forecasts into its mission priorities. Indeed, the word out is there aren't even enough redundant systems - including in situ for protection on the planet - to ensure the survival of any potential crew. Given this it's still puzzling how so many thousands could have even signed up.
Let's be clear the Sun is always emitting a continuous stream of charged particles, mainly electrons and protons, which form the solar wind. Occasionally, eruptions called coronal mass ejections occur, with higher density, energy and speed of the ejected particles. As I have written in multiple previous posts these events vary in strength. Strong CMEs 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. Forecasting them has become a priority in space weather and space physics research.
Sonal 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 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."
The AAS report states that analysis of the Martian solar storm data is just beginning. According to MAVEN Principal Investigator Bruce Jakosky of the University of Colorado -Boulder:
"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."
What is even more critical for future Mars' exploration is predicting the occurrence of such storms to ensure any astronauts on the planet's surface have ample time to secure shelter - especially from the intense radiation of a major CME.