Investigating Mercury's Dust Ring

To begin with Mercury, researchers Guillermo Stenborg and Russell Howard sought to locate a theorized dust-free zone near the Sun, where high temperatures could vaporize dust. Utilizing data from NASA’s STEREO (Solar and Terrestrial Relations Observatory) satellite, they meticulously analyzed images captured by the satellite to identify dust surrounding the Sun. This research aimed to better understand the environment the Parker Solar Probe would encounter during its seven-year mission to sample the solar corona. (The Parker Solar Probe is indeed fascinating.)

“We’re not really dust people,” remarked Howard, the lead scientist for the cameras on both STEREO and the Parker Solar Probe. “The dust near the Sun appears in our observations, but generally, we’ve disregarded it.”

While developing a model to identify dust-free zones in the images, the team observed some areas of the dust cloud were notably brighter. Specifically, they detected a ring around the Sun that was approximately five percent brighter, coinciding with Mercury’s orbit. Previously, it was believed that Mercury's proximity to the Sun and its small size would prevent it from capturing a dust ring.

The Venusian Dust Cloud and Hidden Asteroids

Information related to Venus suggests the presence of previously undetected asteroids in its orbit. Similar to Earth, Venus also resides in a substantial dust ring; however, the dust surrounding Earth has a well-known origin—asteroids from the outer asteroid belt.

Interestingly, around five percent of the asteroids identified on Earth originate from a single source: Vesta. While it may seem improbable for asteroids located between Mars and Jupiter to end up on Earth, they do so surprisingly often. Our knowledge about Vesta, in fact, is significantly derived from the numerous fragments found on our planet's surface. There’s a three-step process that facilitates the transfer of material from a massive impact on Vesta, which occurred less than a billion years ago, into orbits that eventually intersect with our own.

In this instance, researchers identified an orbital dust ring around Venus, akin to Earth’s. However, they struggled to devise a model that could account for such a ring's existence. It appears that Jupiter does not seed asteroids into Venus’s orbit in the same manner; the inner planets' orbital insertion becomes increasingly challenging due to the speed requirements. Additionally, getting close to the Sun adds further complications.

This video explains the unique discovery of unusual rings around Mercury and Venus.

Asteroids in a 1:1 Orbital Resonance

If Venus hasn't drawn material from the asteroid belt, where do these asteroids originate? Astronomers propose that a small group of asteroids exists in a 1:1 orbital ratio with Venus, positioned on the far side of its orbit at any given moment. Such asteroids could have easily evaded detection. Observing the inner solar system proves challenging due to our limited view, as we are looking near the Sun.

This video showcases the accidental discovery of a dust ring around Venus by the Parker Solar Probe.

While the total amount of dust in Venus's orbit is minimal—if consolidated into a single rock, it would form an asteroid slightly over two miles wide—researchers theorize that a small group of asteroids in the correct resonance orbit could have persisted since the solar system's formation, contributing to the dust cloud with primordial elements.

Although such asteroids could theoretically result from planetary collisions, their hypothesized location in a 1:1 orbital resonance on the opposite side of Venus's orbit makes this unlikely. Any debris propelled into space by a significant impact—similar to what may have formed Earth’s Moon—would likely have fallen back to Venus or been drawn into the Sun. Furthermore, Venus's dense atmosphere significantly decelerates incoming or outgoing materials.

Now Explore: The Final Stunning Panorama from Opportunity on Mars, Potential for 50 Billion Rogue Planets in Our Galaxy, and New Studies Indicating Our Galaxy Weighs 1.5 Trillion Solar Masses.

Originally published at www.extremetech.com on March 15, 2019.