Moons of Mars binary asteroid that separated under tidal forces. Phobos could be a second-generation Solar System object that coalesced in orbit after Mars formed, rather than forming concurrently out of the same birth cloud as Mars. Another hypothesis is that Mars was once surrounded by many Phobos- and Deimos-sized bodies, perhaps ejected into orbit around it by a collision with a large planetesimal. The high porosity of the interior of Phobos (based on the density of 1.88 g/cm, voids are estimated to comprise 25 to 35 percent of Phobos' volume) is inconsistent with an asteroidal origin. Observations of Phobos in the thermal
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