NASA’s MESSENGER orbiter, the first spacecraft to orbit planet Mercury, revealed that comet Encke periodically hits the planet with a meteor shower. On Earth, comet Encke also produces multiple meteor shower events every year such as Northern Taurids in late October (aka Halloween Fireballs).
The MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) orbiter found that regular meteor showers occurred within planet Mercury’s exosphere by analyzing a very thin halo of gases surrounding the planet.
Rosemary Killen, one of the findings’ authors and planetary scientist at a NASA’s flight center in Maryland, said that a possible discovery of a meteor shower at Mercury was both exciting and important since the dust and plasma exosphere around Mercury was relatively unexplored.
Meteor showers emerge when a planet’s atmosphere gets in contact with an asteroid’s debris field or a comet’s tail or trail of cosmic debris. Comet tails are made of cosmic debris such as dust, small pieces of ice and rock that are pushed away from the sun by solar radiation. The larger pieces of this debris get caught in the comet’s orbit as debris fields, where many tiny meteoroids are forming and later drop onto planets.
Earth also gets a lot of meteor showers during a year. In summer, comet Swift–Tuttle’s debris field creates the Perseids in the Northern hemisphere, while in December an asteroid delights us with Geminidis meteor shower. Comet Encke has several debris fields across the solar system so on Earth it creates the Taurids meteor shower both in summer and late fall.
MESSENGER data showed that during the past nine years the spacecraft has been orbiting Mercury several surges of calcium occurred repeatedly in Mercury’s exosphere each season. Scientists say that these surges of calcium represent footprints of meteor showers regularly hitting the planet. MESSENGER detected the invisible calcium surges with its Mercury Atmospheric and Surface Composition Spectrometer.
Scientists also say that periodic meteoroid and interplanetary dust showers renew the gases in Mercury’s outer atmosphere by releasing small particles of calcium on impact with its surface. The process is called vaporization. However, NASA experts suggest that interplanetary dust and meteoroids hitting the planet are not enough to account for periodic spikes in calcium levels. There’s an additional source – the meteor showers on Mercury that are caused by a comet’s cosmic debris field. The only comet to hold such a debris field was comet Encke.
Joseph Hahn, a planetary scientist and coauthor of the findings, said that if the above mentioned theory proved right, Mercury was a giant dust collector that got a “steady siege” both from interplanetary dust and comet Encke’s debris trail.
Image Source: Windows to the Universe