Researchers found Mercury, the closest planet to the Sun, experiences periodic meteor showers.
A team of scientists made the discovery by looking at a thin halo of gas that makes up the super-hot planet's exosphere. The findings were made using NASA's MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) spacecraft.
"The possible discovery of a meteor shower at Mercury is really exciting and especially important because the plasma and dust environment around Mercury is relatively unexplored," said Rosemary Killen, a planetary scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland, and lead author of the study, available online in Icarus.
Meteor showers occur when a planet passes through rocky debris left behind by a comet or asteroid. These bits of rocks and dust are pushed away from the Sun by solar radiation. Earth experiences multiple meteor showers per year, and this new research suggests Mercury may see similar events.
Measurements taken by MESSENGER's Mercury Atmospheric and Surface Composition Spectrometer found surges of calcium in mercury's exosphere over the first nine years since the craft started its orbit, this suggests the presence of a meteor shower. The spike is believed to occur when a shower of dust particles hit the planet and knock calcium particles free from the surface.
"If our scenario is correct, Mercury is a giant dust collector," said Joseph Hahn, a planetary dynamist in the Austin, Texas, office of the Space Science Institute and coauthor of the study. "The planet is under steady siege from interplanetary dust and then regularly passes through this other dust storm, which we think is from comet Encke."
The team created detailed computer simulations to test whether or not the calcium spikes were caused be comet Encke , but found the data was a bit off from what was expected. The researchers believe this is due to the gravitational pulls of Jupiter and other planets.
"The variation of Mercury's calcium exosphere with the planet's position in its orbit has been known for several years from MESSENGER observations, but the proposal that the source of this variation is a meteor shower associated with a specific comet is novel," concluded MESSENGER Principal Investigator Sean Solomon, of the Lamont-Doherty Earth Observatory at Columbia University in New York. "This study should provide a basis for searches for further evidence of the influence of meteor showers on the interaction of Mercury with its solar-system environment."
