According to a newstudy, the planet Mercury experiences regular meteor showers atroughly the same time each year, as it moves through a trail of dustthrown off by the ancient comet Encke. The work was presentedat the annual Meeting of the Division of Planetary Sciences of theAmerican Astronomical Society at National Harbor, Maryland.
On any given night youstand a decent chance of catching sight of a meteor – one ofcountless tiny grains of dust that are thrown off in the wake of apassing comet, that burn up in our atmosphere, creating a visiblestreak of light that has given birth to the moniker, shooting star.
Earth is not the onlyplanet to be showered with extraterrestrial materials. In October2014, MAVEN recorded the effects of tons of comet material raining down on the Martian atmosphere from Siding Spring.
For planets likeEarth, that boast very thick atmospheres, the phenomenon isrelatively inconsequential, but for other bodies, like Mercury –which is shrouded by a tenuous cloud of atomic particles known as asurface boundary exosphere – the passing of a comet can have asignificant impact on atmospheric composition.
The recent studyfocused on an analysis of data collected by NASA's MErcury SurfaceSpace ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraftas it orbited the planet from March 2011 up to its demise in Aprilthis year. Over the course of its operational life, MESSENGER wasable to observe the interaction between dust particles thrown off bythe comet Encke, and the altering composition of the planet's fragilesurface boundary exosphere.
It was discovered thatthere was a clear pattern in Mercury's atmospheric calcium levelsthat repeated each year at around the same time. It was theorizedthat dust thrown off by Encke over thousands of years was strikingMercury as it swept through the comet's orbital path, throwing upcalcium from the planet's surface.
However, the timing ofthe closest point of interaction between the orbits of Mercury andEncke occurred roughly a week after the yearly calcium peak observedby MESSENGER. This meant that the comet's dust trail must havesomehow deviated from Encke's extremely stable orbital path, whichbrings it within 31 million miles (50 million km) of the Sun onceevery 3.3 years.
To solve the mystery, ateam of researchers ran complex computer simulations taking in toaccount the most accurate estimations of Encke's orbital path overthousands of years, and the behaviour of the dust stream this wouldhave created. From the simulations, it appears likely that thedeviation is likely the result of the subtle force exerted onparticles by sunlight from our star.
Based on this analysis,it is theorized that the dust particles currently striking Mercurymeasure around 1 mm in size, and where dispersed by Encke between 10– 20 thousand years ago. These particles would have been just theright size for the influence from the Sun to shift their orbit to thecorrect location to account for the calcium spikes.
The study of comets hasbeen a popular subject of late thanks to the incredible success ofESA's Rosetta mission, and research of the type outlined aboveprovides a wider viewing lens for some of the more subtle impactsthat the celestial wanderers have on the planets that make up oursolar system.
Source: NASA