Deimos and Phobos Interior Explorer that the moons of Mars may have formed after a huge collision with a protoplanet one third the mass of Mars that formed a ring around Mars. A third hypothesis is that they may have co-accreted with the parent planet. DePhine mission would explore the origin and the evolution of the two Martian satellites, by focusing on their interior structures and diversity. The mission would attempt to determine if Phobos and Deimos true siblings, originating from the same source and sharing the same formation scenario. It would also determine if both natural satellites are rubble piles or solid bodies, and
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