Dark lightning is also known as “terrestrial gamma-ray flashes.” Thunderstorms not only produce electricity through visible lightning—they also produce powerful flashes of radiation through silent dark lightning that’s nearly invisible. Gamma ray emissions are typically associated with nuclear explosions, supermassive black holes, and supernovas. So it was a surprise to find these emissions coming from thunderstorms.
While visible lightning moves from cloud to cloud or between cloud and ground in a bolt formation, dark lightning flies upward in all directions toward space, including into the airspace where commercial planes fly. If you’re a frequent flier, you may be getting blasted with radiation more often than you realize. We also know that dark lightning spews space with positrons, the antimatter equivalent of electrons.
Scientists believe your radiation dose from a hit of dark lightning is probably equivalent to having a CT scan, but they don’t know for sure. If you receive enough radiation one time or cumulatively, your body might be damaged by dark lightning. But you won’t suffer the noticeable harm that occurs with a direct hit by visible lightning.
The risk of being zapped by dark lightning is small because airline pilots try to avoid flying through thunderstorms. “Doses never seem to reach truly dangerous levels,” said physicist Joseph Dwyer. “The radiation from dark lightning is not something that people need to be frightened about, and it is not a reason to avoid flying. I would have no problem getting on a plane with my kids.” space travel space science earth science space station science space travel space science earth science space station
There’s a lot we don’t know about dark lightning. Although we believe it’s produced when high-energy electrons smash into air molecules during a thunderstorm, we don’t know exactly how visible lightning and dark lightning are related. We also aren’t sure how often dark lightning occurs or if anyone has ever been hit by it.
Mysterious Bright Spots On Ceres
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Previously, we told you that Feature 5, a bright spot on the surface of dwarf planet Ceres, might be a cryovolcano, a water-erupting volcano that may indicate an underground ocean. Now, newer pictures from NASA’s Dawn spacecraft are adding to the mystery.
First, we saw another bright spot, called “Feature 1,” on Ceres’s surface. But the two spots looked different when viewed in thermal images. Feature 1 showed up as a dark spot in infrared images, meaning it was cooler than the area surrounding it. However, Feature 5 didn’t appear at all in thermal images, so its temperature was the same as its surroundings. We don’t know what this means yet. It may be that the spots are made of different material or the ground surrounding them is different.
The next round of images only deepened the mystery. Instead of only two spots, we found that the spots are actually several separate bright points of various sizes that have a central cluster. The brightest spots are contained in a crater about 90 kilometers (55 mi) wide.
“The bright spots in this configuration make Ceres unique from anything we’ve seen before in the solar system,” said Christopher Russell, who leads the Dawn mission. “The science team is working to understand their source. Reflection from ice is the leading candidate in my mind, but the team continues to consider alternate possibilities, such as salt.”
Ceres is also missing the large surface craters that we expected to see. “When we compare the size of [Ceres’s] craters with those we see on [protoplanet] Vesta, we are missing several larger craters,” said Russell. “That’s something we’ve got to learn more about.”
However, Ceres shows more evidence of activity like landslides and flows on its surface than Vesta does. Ceres also has a steep mountain rising from a rather smooth surface.