This is a concept image of an astronaut preparing to take samples from a captured asteroid. The sun is in the background; NASA wants to know more about electrical activity generated by the interaction of solar wind and radiation with asteroids.
Space may appear empty - a soundless vacuum, but it's not an absolute void. It flows with electric activity that is not visible to our eyes. NASA is developing plans to send humans to an asteroid, and wants to know more about the electrical environment explorers will encounter there.
A solar wind
blown from the surface of the sun at about a million miles per hour flows around all solar system objects, forming swirling eddies and vortices in its wake. Magnetic fields carried by the solar wind warp, twist, and snap as they slam into the magnetic fields around other objects in our solar system, blasting particles to millions of miles per hour and sending electric currents surging in magnetic storms that, around Earth, can damage sensitive technology like satellites and power grids.
On airless objects like moons and asteroids, sunlight ejects negatively charged electrons from matter, giving sunlit areas a strong positive electric charge. The solar wind is an electrically conducting gas called plasma where matter has been torn apart into electrons, which are relatively light, and positively charged ions, which are thousands of times more massive. While areas in sunlight can charge positive, areas in shadow get a strong negative charge when electrons in the solar wind rush in ahead of heavier ions to fill voids created as the solar wind flows by.
The surface of Earth is shielded from the direct effects of this activity by our planet's magnetic field, but airless objects without strong repelling magnetic fields, like small asteroids, have no protection from electrical activity in space.
NASA-sponsored researchers funded by the Solar System Exploration Research Virtual Institute (SSERVI) (formerly the NASA Lunar Science Institute (NLSI)) have developed a new computer model that can predict and visualize the interaction between the solar wind, solar radiation, and the surface of asteroids in unprecedented detail.
"Our model is the first to provide detailed, two-dimensional views of the complex interaction between solar activity and small objects like asteroids, using an adaptive computational technique that makes these simulations highly efficient," said Michael Zimmerman, project lead at the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland.