The planet Mercury is regularly being showered by bits of an ancient comet , according to a new study published in the journalGeophysical Research Letters . The textile was left by comet Encke when it crossbreed the compass of the planet thousands of years ago .
Scientists have noticed how more calcium is resign by Mercury at sealed times of the year . The astronomers thought Encke ( which orbits the Sun every 3.3 years ) was responsible for it , but to prove it , they had to model how the dust was released throughout the comet ’s late story . They discovered that erstwhile stuff from the comet is located in almost the good placement around the electron orbit to explain the supernumerary atomic number 20 maintain .
As the comet ’s fragments seasonally rain on the major planet control surface , they vaporise rocks and release elements into Mercury ’s exosphere . An exosphere is basically a very thin standard pressure , an envelope of molecules surrounding a terrestrial body that are gravitationally bind to it , but they are so spread out that do n’t dissemble like a gasolene . Mercury is small , close to the Sun and very hot , so was n’t able to nurse onto a thick ambiance like ours ,
In the last 30 twelvemonth , scientists discovered that Mercury ’s exosphere contains atomic number 11 , K , atomic number 20 , and atomic number 12 , and proposed even encroachment as the mechanism to replenish the exosphere . Using theMESSENGER probe , scientists light upon that calcium seemed to be more abundant after Mercury ’s airless approach to the Sun ( perihelion ) , but they could not explain why .
Most of the impacts were thought to be acquire byzodiacal dust , fine material grow by comet and asteroid collisions , orbiting in the internal Solar System , because comet Encke ’s current path frustrate Mercury ’s domain a week after the planet ’s perihelion , suggest it was not the cause .
But the researchers wondered if the stream of particles from the comet might have shift over time , so they ran a complex computer simulation modelling how the comet ’s orbit has changed in the last 10,000 years , and examined the subtle interaction between the cometary rubble and sunlight . Using the model , the team picture that the calcium copiousness pinnacle matches with dust turf out by comet Encke between 10,000 and 20,000 age ago .
“ We already know that impacts were important in producing exospheres , ” Dr Rosemary Killen , one of the co - author of the study , said in astatement . “ What we did not know was the relative importance of comet watercourse over zodiacal dust . Apparently , comet streams can have a huge , but periodical , effect . ”
The team now require to explore if the comet detritus affects other elements in Mercury ’s exosphere .
