Jupiter may have ‘sprites’ or ‘elves’ in its atmosphere
This is the first time scientists have seen hints of these bright, fast flashes on another world Jupiter is the first planet other than Earth seen to host what appear to be atmospheric light shows called “sprites” or “elves.”
These two types of atmospheric glows form when lightning alters electric fields in the atmosphere above a storm. On Earth, these events cause high altitude nitrogen molecules to glow red for a moment. Sprites appear in the mesosphere, at heights of about 50 to 90 kilometers (31 to 56 miles). They can light up the sky for tens of kilometers (miles). Elves are far bigger. They can span hundreds of kilometers. They also form at greater heights — 75 to 105 km. That’s solidly within the lower thermosphere.
Scientists thought sprites and elves also might dance above other planets that crackle with lightning. But until now, no one had glimpsed these lights on another world.
NASA’s Juno spacecraft started orbiting Jupiter in 2016. Since then, Juno has seen 11 flashes of light on the gas giant that could be sprites or elves. These flares appeared above Jupiter’s water clouds, where most lightning forms. Juno saw several in regions known to be stormy.
Each flash lasted milliseconds. That’s about as long as sprites and elves last on Earth. And the flashes glowed in ultraviolet light. This is the wavelength band in which any sprites or elves on Jupiter would be expected to glow. It’s different from the red hues of sprites and elves on Earth. Why? Unlike Earth, Jupiter’s atmosphere is mostly hydrogen, not nitrogen.
Researchers reported the flashes online October 27 in the Journal of Geophysical Research: Planets.
Juno could confirm that these lights are sprites or elves with more observations, says Rohini Giles. She is a planetary scientist at the Southwest Research Institute in San Antonio, Texas. If Juno saw a lightning strike at the same place as one of these ultraviolet flashes, “that would prove it,” she says.
Juno may also reveal the size of those light shows if it manages a closer look at one of the flashes. Knowing how big they are could tell scientists which the lights are — sprites or elves. Or maybe even both.
Power Words
cloud: A plume of molecules or particles, such as water droplets, that move under the action of an outside force, such as wind, radiation or water currents. (in atmospheric science) A mass of airborne water droplets and ice crystals that travel as a plume, usually high in Earth’s atmosphere. Its movement is driven by winds.
electric field: A region around a charged particle or object within which a force would be exerted on other charged particles or objects.
gas giant: A giant planet that is made mostly of the gases helium and hydrogen. Jupiter and Saturn are gas giants.
hydrogen: The lightest element in the universe. As a gas, it is colorless, odorless and highly flammable. It’s an integral part of many fuels, fats and chemicals that make up living tissues. It’s made of a single proton (which serves as its nucleus) orbited by a single electron.
Jupiter: (in astronomy) The solar system’s largest planet, it has the shortest day length (10 hours). A gas giant, its low density indicates that this planet is composed of light elements, such as hydrogen and helium. This planet also releases more heat than it receives from the sun as gravity compresses its mass (and slowly shrinks the planet).
lightning: A flash of light triggered by the discharge of electricity that occurs between clouds or between a cloud and something on Earth’s surface. The electrical current can cause a flash heating of the air, which can create a sharp crack of thunder.
mesosphere: The highest part of Earth’s atmosphere where all of the gases are all still well-mixed, not merely layered on the basis of each gas’s mass. This layer is right above the stratosphere. It’s the uppermost layer of the atmosphere with enough gas to cause friction for incoming space rocks. That’s why this region is where most meteor’s burn up. It varies somewhat in height, but tends to span from 64 to 85 kilometers (31 to 53 miles) above Earth’s surface. The upper level of this part of the atmosphere is known as the mesopause, or Karman line.
thermosphere: An upper region of the atmosphere that extends from 85 to 600 kilometers (53 to 372 miles) above Earth’s surface. In the thermosphere, temperature increases with height because of the sun’s energy. It's upper boundary is known as the thermopause.
ultraviolet light: A type of electromagnetic radiation with a wavelength from 10 nanometers to 380 nanometers. The wavelengths are shorter than that of visible light but longer than X-rays.