Heliosphere Crucial to Future Moon/Mars Missions

As the space race continues to push the boundaries of outer space with missions to the Moon and Mars, it still remains a unclear how much risk the heliosphere, the magnetic layer that emanates out from the sun, poses to humankind.

"In order to get to Mars, spacecraft and humans will be immersed in the heliosphere and will have to contend with it," said Terry Onsager, program scientist at NASA headquarters. "That environment can be a harsh one, but one we're ready for."

For many years now, scientists have been mapping the heliosphere to find a way that will help future mission navigate safely. Once astronauts leave Earth’s magnetosphere, they are exposed to dangerous solar radiation, which can harm living tissue.

"Periodically, solar eruptions on the sun's surface can generate enormous increases in the energetic particle radiation environments, and when that occurs, systems need to be able to handle that," Onsager said.

Some scientific developments are being implemented: spacecraft are being built with warning systems and equipment that can withstand solar radiation and provide areas for the crew to hide in during solar storms.  

At the same time, NASA’s Solar Dynamics Observatory (SDO) continuously monitors the activity of the sun. Scientists take images that allow them to monitor the surface conditions to build forecast models for eruptions of solar energetic particles. Astronauts usually have 30 minutes once the eruption has begun to act, as that’s the time it takes the eruption to reach its peak.

Predicting the weather in space is not at all similar to predicting the weather on Earth. SDO and NASA heliophysics missions observe the sun around the clock. They build statistical correlation models to predict the possibility of a solar eruption.

"Forecasting space weather phenomena, whether at Earth or in deep space, is very, very complex," said Jingnan Guo, heliophysicist at Germany’s University of Kiel. "We have to consider scales from the sun-Earth distance—about 93 million miles, at which waves and erupted material propagate across space—to below a few meters, at which scale you see the turbulence and kinematics of the particles."

Scientists have a long road ahead: even the best predictive models are currently in the early stages of development. Multi-point observations are especially important to understanding how solar energetic particles travel through the solar system. Knowing exactly how radiation spreads will help keep astronauts on Moon and Mars missions safe.

"If you have just a single point observation, it's very hard to model or even, sometimes, interpret the data. If you have multiple points, than you can constrain your model and make sure the underlying theories are capable of reproducing that event," said Leila Mays, a space weather scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland.

While the round-the-clock studies will continue from instruments on the ground and on NASA’s spacecraft, it is expected that future missions will also supply scientists with information that will lead to better predictive models. One particle measurement instrument on the Curiosity Rover is currently measuring radiation on Mars; the Lunar Orbital Platform-Gateway, expected to launch in the next few years, will also be equipped to take radiation measurements.

"Future deep-space human exploration vehicles provide not only the ability to safeguard the crew onboard, but simultaneously do new scientific experiments," said Antti Pulkkinen, scientist at NASA's Goddard Space Flight Center. "They will serve this dual purpose."

The Moon’s atmosphere – the so-called exosphere, comprised of hydrogen, helium, neon and argon – is also of particular interest to scientists, as plenty of Moon missions are planned for humanity’s foreseeable future. The upper layer of the Moon’s exosphere is made up on the ionosphere, a thin layer created by sunlight.

"The ionosphere is a million times less dense than the ionosphere of Earth so it's really hard to directly measure those charged particles," said Jasper Halekas, ARTEMIS scientist at the University of Iowa in Iowa City. New Moon missions would provide more insight into both the ionosphere and the atmosphere, and help scientists understand the relationship and interaction between the atmospheres of the Earth and the Moon.

While scientists cannot foretell exactly what discoveries future Moon and Mars missions will bring, but they do know that heliophysics will play a significant role in protecting the astronauts and making those journeys possible.

Photo credit: NASA

Jessica Zeitz