The first measurements of Mercury planet's movements from a spacecraft orbiting the planet reveal new information about the make up of solar system's innermost world and its interactions with other planets.
Mercury does not rotate on its axis smoothly. but it experiences regular fluctuations in speed over an 88-day cycle which is a year on the planet. These fluctuations are caused by the planet's interactions with the Sun as it moves around it. The gravitational pull of Sun speeds up or slows down the Mercury's rotation depending on where the oblong shaped planet is on its elliptical orbit.
The new study details new measurements of Mercury's movements taken by the MESSENGER Spacecraft, which orbited the planet for more than four years before its propellant was exhausted and it purposefully crash landed on Mercury in April, 2015. The new measurements from the spacecraft show that Mercury is spinning on its axis about 9 seconds faster than scientists had previously calculated, It is not a huge difference but it is un expected.
The previous studies showed that Mercury rotates 3 times on its axis for every two revolutions around the Sun indicating that Sun was influencing the Mercury's spin. The new study shows that Mercury has a more complex rotational behavior.
The scientists think that the rotational speed could come from Jupiter's large gravity field tugging on Mercury's orbit, changing the planet's distance to the Sun and its influence on its spin. The authors of the new study propose that Jupiter, which travels around the sun roughly once every 12 years, has superimposed a 12-year, long-term libration on top of Mercury’s 88-day libration. This long-term libration could be causing the slight increase in speed observed during the time period of the new study and also cause a slow-down in Mercury’s spin at other times, according to the study’s authors.
Mercury does not rotate on its axis smoothly. but it experiences regular fluctuations in speed over an 88-day cycle which is a year on the planet. These fluctuations are caused by the planet's interactions with the Sun as it moves around it. The gravitational pull of Sun speeds up or slows down the Mercury's rotation depending on where the oblong shaped planet is on its elliptical orbit.
The new study details new measurements of Mercury's movements taken by the MESSENGER Spacecraft, which orbited the planet for more than four years before its propellant was exhausted and it purposefully crash landed on Mercury in April, 2015. The new measurements from the spacecraft show that Mercury is spinning on its axis about 9 seconds faster than scientists had previously calculated, It is not a huge difference but it is un expected.
The previous studies showed that Mercury rotates 3 times on its axis for every two revolutions around the Sun indicating that Sun was influencing the Mercury's spin. The new study shows that Mercury has a more complex rotational behavior.
The scientists think that the rotational speed could come from Jupiter's large gravity field tugging on Mercury's orbit, changing the planet's distance to the Sun and its influence on its spin. The authors of the new study propose that Jupiter, which travels around the sun roughly once every 12 years, has superimposed a 12-year, long-term libration on top of Mercury’s 88-day libration. This long-term libration could be causing the slight increase in speed observed during the time period of the new study and also cause a slow-down in Mercury’s spin at other times, according to the study’s authors.
Margot said the influence of Jupiter on Mercury is only one possible explanation for the new observations and additional measurements could unveil additional influences on the planet. The European Space Agency’s BepiColombo mission to Mercury launching in 2017 may be able to answer some of these questions, according to the study’s authors.
“It’s still a bit of a puzzle,” Margot said.
