Last week, as the sun crackled with flare activity and launched a succession of coronal mass ejections, it wasn't only Earth that felt the sun's wrath.
Currently gliding its way toward Mars, NASA's Mars Science Laboratory detected the sun's temper tantrum — radiation carried by the CME that was launched Jan. 22 washed over the robot.
Wrapped up snugly inside its "cruise phase" capsule, the rover — nicknamed "Curiosity" — wasn't sleeping, however. One of her 11 instruments was switched on to measure the radiation environment of interplanetary space.
The Radiation Assessment Detector, or RAD, is a coffee can-sized detector that will collect radiation data on the Martian surface after Curiosity lands Aug. 6. This information will then be used by NASA to better understand how to protect future Mars astronauts from this potentially deadly hazard.
But during the journey to Mars, spaceships are bathed in high-energy particles constantly streaming from the sun. And during times of increased solar activity, solar flares and CMEs can intensify the radiation dose, boosting the risk of damage to sensitive electronics and biology. The RAD's work has already begun.
"We only have a few hours of data downloaded from the RAD so far, but we clearly see the event," said RAD principal investigator Don Hassler of the Southwest Research Institute in San Antonio, Texas. "This (solar particle event) encounter is particularly exciting in light of the alignment between the Earth, MSL and Mars right now and for the next few months. It will be very interesting to compare the RAD data, collected from inside the capsule, with the data from other spacecraft."
Indeed, solar physicists and space weather scientists will be very interested in the RAD measurements. During solar storms, the more spacecraft measuring the radiation being kicked off from the sun, the better. Understanding the nature of CMEs as they travel through space can improve space weather models and help us predict the impact of future CMEs on Earth and assets in deep space.
"RAD was designed to characterize radiation levels on the surface of Mars, but an important secondary objective is measuring the radiation during the almost nine-month journey through interplanetary space to prepare for future human exploration," Hassler said. "Not only will this give us insight into the physics of these giant clouds, but like an astronaut, RAD is tucked inside the MSL 'spacecraft. Measurements from RAD will give us insight about the shielding provided by spacecraft for future manned missions in deep space."
According to the NOAA's Space Weather Prediction Center, this most recent solar radiation storm was the largest since the Halloween Storms of 2003. So it seems Curiosity was in the right place at the right time, beginning its mission not on the surface of Mars, but in radioactive interplanetary space.
Image: The sun kicks off a CME into interplanetary space. (Credit: NASA/SDO).