Mercury and Mars: The Unlikely Twins

Team Exploriments has created an app for iPad that deals with Newton's Law of Universal Gravitation. It facilitates an understanding of the concepts and formulae that underlie gravitation. You can now explore gravitation the Exploriments way - by using the power of simulation.

While working on this app we noticed something interesting - to one decimal place, Mercury and Mars have the same value for acceleration due to gravity - 3.7 m/s! In a solar system with planets of wildly differing sizes, densities and masses, this is a striking coincidence. Interestingly, a recent
theory posits that Mercury and Mars were created from the leftovers of an early violent interaction between Earth and Venus. So far, there is no science that connects their g values to them being joined at the hip at birth - but feel free to air your views.

What are the implications of having the same value of "g"? 

For one thing, objects would weigh the same on both planets and would fall at the same rate.
Applying Newton's Law leads us to a more involved conclusion, as shown in this short worksheet:

mercury = G x Mmercury/(Rmercury)2 = gmars = Mmars/(Rmars)2 = 3.7

mercury/(Rmercury)2 = Mmars/(Rmars)2

The M/R
2 ratio of both the planets is the same. You can do the exercise of plugging in the known values of Mars and Mercury to verify this simple, yet interesting fact that makes these two planets unlikely twins. Are you aware of other surprising coincidences linking Mars and Mercury, or other gravitation factoids that you would like to share?

1 comment:

  1. This is just freaky coincidence. Shouldn't read too much into it. Know a coincidence when you see one.