Astrophysicists from the Naval Research Laboratory in Washington, D.C. accidentally came upon the observable trail of cosmic dust forming a ring nearly 15 million km wide around Mercury while trying to develop new techniques to research solar activity for forecasting purposes.
While similar rings of space dust have long been known to exist around Earth and Venus, it was previously assumed that Mercury did not have one.
"People thought that Mercury, unlike Earth or Venus, is too small and too close to the Sun to capture a dust ring," study coauthor Dr. Russell Howard explained. "They expected that the solar wind and magnetic forces from the Sun would blow any excess dust at Mercury's orbit away," he noted.
Using NASA's Solar and Terrestrial Relations Observatory (STEREO) satellite and the Parker Solar Probe, what they found was an increased level of brightness circling Mercury, calculating an excess concentration of dust of about 3-5 percent at the ring's center.
"It wasn't an isolated thing," Dr. Howard emphasized. "All around the Sun, regardless of the spacecraft's position, we could see the same five percent increase in dust brightness, or density. That said something was there, and it's something that extends all around the Sun," he noted.
The astrophysicists' findings have important implications for traditional conceptions of the effects of gravity in the solar system, not to mention the ability of ancient space dust of the same kind as that which formed Earth to 'survive' so close to the Sun.
Dr. Mark Kushner, an astrophysicist from the Goddard Space Flight Center and coauthor of a separate study hypothesizing that a group of never-before-seen asteroids co-orbiting Venus was causing a similar ring of space dust to form around that planet, said the space dust research was "exciting," since it was based on new information that was "right in our neighbourhood."
"It's not every day you get to discover something new in the inner solar system," he said.here and here.
Ultimately, NASA observes that coming to a more precise understanding of the physics governing ancient dust rings like those around Mercury and Venus in our solar system can be extrapolated for use in the study of distant solar systems, their hidden planets, and even their orbital properties.