[Illustration: 89. An Apollo lunar sample return container. In this view, the rock box contains sample material and core tubes.] Apollo Command Module: Skylab 4 [Illustration: 90. _Skylab 4_ Command Module is hoisted aboard the U.S.S. _New Orleans_ after completing 1214 orbits.] The _Skylab 4_ command module ferried the crew of the last Skylab mission—astronauts Gerald P. Carr, Edward G. Gibson, and William R. Pogue. The _Skylab 4_ crew lived in the Skylab for 84 days, from November 16, 1973, to February 8, 1974. In flight, the Apollo command module operated with a service module—an equipment section, 7.4 meters (24 feet) long and 4 meters (13 feet) in diameter—attached to the command module. The service module provided electrical power, oxygen, and water for the command module for most of a typical flight. In addition, the service module contained the 9300-kilogram (20,500-pound) thrust Service Propulsion System, an engine capable of being throttled and restarted. During Apollo lunar flights, the engine provided thrust for mid-course trajectory changes and boosted the command/service module combination out of lunar orbit and back to Earth. The service module was jettisoned just before reentry into the earth’s atmosphere. During reentry, the command module’s exterior was subjected to temperatures of around 2800°C (5000°F). The command module is covered with an ablative heat shield composed of a phenolic epoxy resin in a fiberglass honeycomb structure. As friction with the earth’s atmosphere caused the heat shield to char and vaporize, the heat was carried away from the spacecraft. The heat shield varies in thickness from 7 centimeters (2.75 inches) at the base to .6 centimeter (.25 inch) at the forward section. Total weight of the heat shield is about 1400 kilograms (3000 pounds). The prime contractor for the Apollo Command Module was North American Rockwell Corporation. The command module is from the National Aeronautics and Space Administration. Diameter 3.9 m. (12 ft., 10 in.) max. Length 3.2 m. (10 ft., 7 in.) Moon Rocks [Illustration: 91. A sample of vesicular basalt, produced by lunar volcanism 3.7 billion years ago, in the Lunar Receiving Laboratory. Devices record size and orientation of the rock. The cavities in this sample were formed by gases escaping from the still-molten rock. This sample is 13.5 centimeters (5.5 inches) long. A fragment of this lunar rock is on display in the “Apollo to the Moon” gallery.] During the six Apollo program moon landings, astronauts collected and returned to Earth samples of the lunar surface. The samples were collected both from the flat maria regions—great basins created by ancient meteoric impacts and later filled with lava from the moon’s interior—and from the highland regions.