Apparent retrograde motion notable on Mars which has two natural satellites, Phobos and Deimos. Both moons orbit Mars in an eastward (prograde) direction, however Deimos has an orbital period of 1.23 Martian sidereal days, making it supersynchronous, whereas Phobos has an orbital period of 0.31 Martian sidereal days making it subsynchronous. Consequently, although both moons are travelling in an eastward (prograde) direction, they appear to be travelling in opposite directions when viewed from the surface of Mars due to their orbital periods in relation to the rotational period of the planet. All other planetary bodies in the Solar System also appear to periodically
Two Is Better Than One and join. A music video ecard was also released for the song. The single was sent to mainstream radio in the United States on October 19, 2009. FMQB Mainstream Releases "Two Is Better Than One" debuted at number 92 on the "Billboard" Hot 100. It fell off the following week but re-entered at number 79 and rose the following week to number 64. After a few weeks, the song then reached its peak at number 18 on the chart. It has since become Boys Like Girls' third top 40 on the Hot 100 as well as Swift's twenty-first entry in