The pyramid-shaped glow of “zodiacal light” is caused by sunlight reflecting off interplanetary dust … [+]
Have you ever seen the Solar System glow? Look to the western sky an hour after sunset from a dark-sky destination and—only during late February and March—you’ll see a delicate triangular column of light extending up from the horizon.
It’s called “zodiacal light,” and for a long time it was thought to be the result of cosmic dust left in the Solar System by asteroids and comets.
Now a team of scientists have come up with a new theory; it’s Mars shedding dust into interplanetary space.
Detections of dust by NASA’s Juno spacecraft at Jupiter during its journey from Earth suggest that “zodiacal light” is actually “Mars light.”
Just published in the Journal of Geophysical Research: Planets, the paper containing these claims is based on data collected by four star trackers—cameras on Juno—that help its instruments remain accurate while studying Jupiter’s magnetic field.
The star trackers’ designer, John Leif Jørgensen—a professor at the Technical University of Denmark—programmed one of them to send back images of asteroids during its long journey to Jupiter from 2011 through 2016.
What he got were thousands of images containing streaks. “The images looked like someone was shaking a dusty tablecloth out their window,” said Jørgensen, who feared the spacecraft may have a leak.
However, what was actually happening was cosmic dusk hitting Juno’s solar panels at 10,000 miles/16,000 kilometers per hour.
Most of the dust streaks were occurring when Juno was between Earth and the main asteroid belt, which is found between Mars and Jupiter. The data also showed that dust detection cease past Mars—the dustiest planet in the Solar System. “The natural thought is that Mars is a source of this dust,” said Jørgensen.
What’s still a mystery is how all that dust escapes the red planet’s gravity.
The Martian dust cloud is kept within the inner Solar System by Jupiter’s gravitational influence, and it 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 Jørgensen.
Measuring the distribution of this dust cloud, the researchers found that it’s consistent with the variation of zodiacal light that has been observed from Earth.
It’s easy to see under certain conditions—and easiest at this time of year.
Detections of dust by NASA’s Juno spacecraft at Jupiter during its journey from Earth suggest that … [+]
Zodiacal light is the biggest object in the Solar System and it’s at its brightest and best around the equinoxes. It’s visible along the ecliptic, the apparent path the Sun takes through the sky.
Known as the “false dusk” in March, it’s also visible before dawn in the east during September when it’s called the “false dawn.”
To see it you need a very dark site and for there to be no clouds on the horizon. It’s visible for about 90 minutes.
It’s called “zodiacal light” because it’s always visible over the constellations of the zodiac. That still applies, but its newly-discovered origin means we should probably now call is something different—“Martian light.”
Wishing you clear skies and wide eyes.
I’m an experienced science, technology and travel journalist and stargazer writing about exploring the night sky, solar and lunar eclipses, moon-gazing, astro-travel,