Apollo 15 plant growth experiment, 1971. Germ-free plants growing in lunar material brought back from the Moon by the Apollo 15 mission. The plants are lettuce (left), tomato (centre left and centre right) and citrus (right). This type of testing was a unique effort at the Manned Spacecraft Center (MSC) to grow germ-free plants. The experiments were carried out by NASA and the US Department of Agriculture's Forest Service. The aim was to establish the exact mineral needs of the plants. The Apollo 15 mission to the Moon took place from 26 July to 7 August 1971. Photographed in October 1971.