Changes

=== Two colors ===

=== Two colors ===

Iapetus is best known for the surprisingly different colors of its leading and trailing hemispheres. Its leading hemisphere has an albedo of about 0.05, while the trailing hemisphere has an albedo as high as 0.6. The dark region is named Regio Cassini, in honor of the discoverer. The bright region is named Roncevaux Terra. The boundary between these two regions is sharp, but not perfectly so. In the border between the two regions, the dark material often covers only one side of a crater or fills the floor of another.<ref name=Arnett>Arnett, Bill. "[http://www.nineplanets.org/iapetus.html Entry for Iapetus]." ''The <s>Nine</s> 8 Planets'', May 13, 2005. Accessed June 16, 2008.</ref>

Iapetus is best known for the surprisingly different colors of its leading and trailing hemispheres. Its leading hemisphere has an albedo of about 0.05, while the trailing hemisphere has an albedo as high as 0.6. The dark region is named Regio Cassini, in honor of the discoverer, and the bright region is named Roncevaux Terra. The boundary between these two regions is sharp, but not perfectly so. In the border between the two regions, the dark material often covers only one side of a crater or fills the floor of another.<ref name=Arnett>Arnett, Bill. "[http://www.nineplanets.org/iapetus.html Entry for Iapetus]." ''The <s>Nine</s> 8 Planets'', May 13, 2005. Accessed June 16, 2008.</ref>

The origin of the dark material remains unsettled. Some astronomers speculate that the material came from [[Phoebe]], a member of the [[Norse group]] of moons. Yet the colors of Phoebe and the dark region of Iapetus are not alike.<ref name=Arnett/><ref name=Hamilton/>

The origin of the dark material remains unsettled. Some astronomers speculate that the material came from [[Phoebe]], a member of the [[Norse group]] of moons. Yet the colors of Phoebe and the dark region of Iapetus are not alike.<ref name=Arnett/><ref name=Hamilton/>