The Juno spacecraft reveals origin of zodiacal light

Today’s Video of the Day from NASA Goddard describes a breakthrough discovery on the origin of zodiacal light, a faint band of light that can be seen in the night sky. The light is visible in the west after twilight and in the east just before dawn. 

Zodiacal light is produced by sunlight reflecting off cosmic dust that is orbiting the Sun. It has been assumed that the cosmic dust was carried into the inner solar system by comets and asteroids, but new observations suggest that the dust may originate on Mars. 

The new theory has emerged after dust particles slammed into the Juno spacecraft during its journey from Earth to Jupiter. According to NASA Goddard, the impacts provided important clues to the origin and orbital evolution of the dust, explaining some mysterious variations of the zodiacal light.

John Leif Jørgensen, a professor at the Technical University of Denmark, designed four onboard cameras – or star trackers – for the Juno spacecraft. In an attempt to survey the sky for asteroids, Professor Jørgensen programned a camera to capture objects that appeared in multiple consecutive images but were not in the catalog of known celestial objects.

The camera abruptly began beaming down thousands of images of unidentifiable objects, which appeared as streaks and then quickly disappeared.

“We were looking at the images and saying, ‘What could this be?’” said Professor Jørgensen.

The Juno scientists considered many potential causes, including the possibility that the camera had caught a leaking fuel tank on Juno. “We thought, ‘Something is really wrong.’ The images looked like someone was shaking a dusty tablecloth out their window,” said Professor Jørgensen. 

When the researchers calculated the size and velocity of the objects in the images, they discovered that dust grains had smashed into Juno at speeds of about 10,000 miles per hour, chipping off tiny fragments of the spacecraft.

“Even though we’re talking about objects with only a tiny bit of mass, they pack a mean punch,” said Jack Connerney, the mission’s deputy principal investigator.

“Each piece of debris we tracked records the impact of an interplanetary dust particle, allowing us to compile a distribution of dust along Juno’s path.”

Further investigation showed that the majority of dust impacts were recorded between Earth and the asteroid belt, with gaps related to the influence of Jupiter’s gravity. The experts determined that the dust cloud ends at Earth because our planet’s gravity sucks up all the dust that gets near it. “That’s the dust we see as zodiacal light,” said Professor Jørgensen.

The outer edge of the dust cloud ends just beyond Mars, which suggests that this dusty planet is the source of zodiacal light. While the Juno scientists cannot yet explain how the dust escaped Martian gravity, they hope that other experts may help to provide them with insight. 

Video Credit: NASA Goddard 

–—

By Chrissy Sexton, Earth.com Staff Writer