Apollo 16 was the second of the Apollo type J missions, featuring the use of the Lunar Roving Vehicle, increased scientific capability, and lunar surface stays of three days. As Apollo 16 was the penultimate mission in the Apollo program and there was no new hardware or procedures to test on the lunar surface, the last two missions (the other being Apollo 17) presented opportunities for astronauts to clear up some uncertainties in understanding the Moon's properties. Although previous Apollo expeditions, including Apollo 14 and Apollo 15, obtained samples of pre-mare lunar material, before lava began to upwell from the Moon's interior and flood the low areas and basins, none had actually visited the lunar highlands.