Analysis of solar activity and its implications for the future exploration of Mars
The Sun is about to reach peak activity this year, offering a rare opportunity to study how solar storms and radiation could affect future astronauts on the Red Planet.
In the coming weeks, two of NASA’s Martian probes will have an unprecedented opportunity to study how solar flares – giant explosions on the surface of the Sun – could affect robots and future astronauts on Mars.
This is because the Sun is entering a period of maximum activity called the solar maximum, a phenomenon that occurs approximately every 11 years. During solar maximum, the Sun is particularly prone to violent explosions in various forms – including solar flares and coronal mass ejections – that hurl radiation into deep space. When a series of these solar events occurs, it is called a solar storm.
The Earth’s magnetic field largely protects our planet from the effects of these storms. However, Mars lost its global magnetic field long ago, making the Red Planet more vulnerable to energetic particles from the Sun. How intense can solar activity get on Mars? Researchers hope that the current solar maximum will give them a chance to find out. Before sending humans to Mars, space agencies must determine, among many other details, what type of radiation protection astronauts would require.
“For humans and equipment on the Martian surface, we don’t yet have a clear understanding of the effect of radiation during solar activity,” said Shannon Curry of the University of Colorado Boulder’s Laboratory for Atmospheric and Space Physics. Curry is the principal investigator for NASA’s MAVEN (Mars Atmosphere and Volatile EvolutioN) orbiter, operated from NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “I would really like to see the ‘big event’ on Mars this year – a large event that we can study to better understand solar radiation before astronauts go to Mars.”
High and low altitude measurement
MAVEN observes radiation, solar particles and more from high above Mars. The planet’s thin atmosphere can affect the intensity of particles by the time they reach the surface, which is where NASA’s Curiosity rover comes in. Data from Curiosity’s Radiation Assessment Detector, or RAD, has helped scientists understand how radiation degrades carbon-based molecules on the surface, a process that could affect the preservation of signs of ancient microbial life . The instrument also gave NASA an idea of how much radiation shielding astronauts could expect by using caves, lava tubes or rock faces for protection.
When a solar event occurs, scientists observe both the amount of solar particles and their energy.
“You can have a million low-energy particles or 10 very high-energy particles,” said RAD principal investigator Don Hassler of the Southwest Research Institute’s Boulder, Colorado, office. “While MAVEN instruments are more sensitive to low-energy instruments, RAD is the only instrument capable of detecting high-energy instruments that can penetrate the atmosphere to the surface, where the astronauts would be ”.
When MAVEN detects a major solar flare, the orbiter team alerts the Curiosity team so they can monitor changes in the RAD data. The two missions can even assemble a time series that measures changes down to a half second as particles arrive in the Martian atmosphere, interact with it, and finally hit the surface.
The MAVEN mission also leads an early warning system that alerts other Martian mission teams when radiation levels begin to increase. The advisory allows missions to turn off instruments that may be vulnerable to solar flares, which can interfere with electronics and radio communication.
The loss of water
In addition to helping keep astronauts and spacecraft safe, studying the solar maximum could also provide insight into why Mars went from being a warm, humid Earth-like world billions of years ago to the frozen desert it is today.
The planet is at a point in its orbit where it is closest to the Sun, which warms the atmosphere. This can cause dust storms to cover the surface. Sometimes storms merge, becoming global.
While little water remains on Mars – mainly ice beneath the surface and at the poles – a certain amount still circulates as vapor in the atmosphere. Scientists wonder whether global dust storms help expel this water vapor, lifting it high above the planet, where the atmosphere is swept away during solar storms. One theory is that this process, repeated enough times over the eons, could explain how Mars went from having lakes and rivers to virtually no water today.
If a global dust storm were to occur at the same time as a solar storm, it would provide an opportunity to test that theory. Scientists are particularly excited because this particular solar maximum occurs at the beginning of the dustiest season on Mars, but they also know that a global dust storm is a rare event.
