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 the top 40. It is also the group's biggest hit to date. By December 2011, "Two Is Better Than One" had sold 1,508,000 copies in the U.S. alone, outselling even other big Taylor Swift hits such as "Tim McGraw" and "Fifteen". As of November 2017, the song has sold 1.7 million copies in the United States. With both related artists receiving acclaim, the song became Boys Like Girls' second consecutive top 40 single on the "Billboard" Hot 100. Also, it gave Swift her twenty-first top 40 song on that chart. For the week of January 9, 2010, the song became