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Our solar system is filled with asteroid dust and comets in ruins, but only some planets are honored with a grainy ring to call. Venus and the Earth both have this pleasure, escorted around the Sun by a band of cosmic matter.
Mercury's little planet, on the other hand, was once considered alone. Pressed against the only source of heat in the solar system, scientists have not even imagined that dust can survive here. But it turned out that we were wrong.
A new study has now identified a vast trail of fine cosmic dust in the orbit of Mercury, forming a ring nearly 15 million kilometers wide.
Without our knowledge, it seems that Mercury has waded in this sea of ancient material, three times larger than his, probably for billions of years.
"People thought that Mercury, unlike Earth or Venus, is too small and too close to the Sun to capture a ring of dust," said co-author Guillermo Stenborg, a solar scientist at the Naval Research Laboratory.
"They expected the solar wind and the magnetic forces of the Sun to chase excess dust out of Mercury's orbit."
In truth, Stenborg and his colleague Russell Howard, a scientist specializing in the field of solar energy working in the same laboratory, discovered their discovery by accident. The team was really looking for holes in the dust, near the sun, where the material should have been sprayed and swept.
It's a bit like looking through a splashed window of rain and trying to find out if it's still raining outside.
With all the dust obscuring our immediate vision, scientists could not find a dust-free space between us and the Sun. From where we sit, it just looks like there is dust everywhere.
The only clues we actually have are the different types of light we see coming back to us. When sunlight bounces off the dust particles in space, it creates a force 100 times brighter than the coronal lumen itself.
Most of the time, scientists reject this data to be able to devote themselves solely to the study of the crown, but this time, the researchers kept it on a whim.
Using images of the interplanetary space of NASA's STEREO satellite, the team built a model that separates the two types of light, calculating the amount of dust actually present.
What they have noticed is an increased brilliance that goes around the Mercury orbit, which implies "a dust density in excess of about 3 to 5% in the center of the ring".
"It was not an isolated thing," explains Howard. "All around the Sun, regardless of the position of the spacecraft, we could see the same 5% increase in brightness or density of dust." That said, there was something there and it's something that extends all around the Sun. "
The results pushed our understanding to the brink. Because if Mercury really navigates in the cosmic dust, this material must be able to get much closer to the Sun than we ever thought possible.
This gives scientists important clues about the composition and origin of the dust itself.
Looking for rings of dust in our solar system is not so different from that of reading dark circles in the forests. Composed of old debris from 4.6 billion years ago, dust clouds in orbit could help us explain what happened since the formation of our solar system.
In fact, scientists believe that all the planets in our system, including the Earth, began as mere grains of dust before being collected by gravity and other forces.
"In order to model and accurately read the dust rings around other stars, we must first understand the physics of dust in our own garden," said Kuchner.
The huge ring of dust that co-orbits Venus is a good start. This month alone, a new newspaper claims to have discovered the true source of Venus' huge ring of dust, made up of grains no bigger than coarse sandpaper.
Using dozens of modeling tools and simulations, the researchers believe that the dust comes from a group of asteroids never seen and co-orbiting the planet.
In addition, the authors argue that this population of ruined asteroids has been feeding the Venus dust core since the childhood of the solar system.
"It's not every day that we discover something new in the internal solar system," says Marc Kuchner, author of the study on Venus and Astrophysicist at Goddard's Space Flight Center. The NASA.
"It's just in our neighborhood."
Both the first and second studies were published in the Letters from the Astrophysical Journal.
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