Mariner IV determined that Mars’ atmosphere is only 1 to 2 percent of the Earth’s in density. This may mean that future manned spacecraft to Mars must employ the same landing technique – retro rockets – as the ones which will be used by the Apollo lunar ship.
Artist’s drawing of interplanetary explorers maintaining contact through the use of small radio equipment. This particular transmitter is also designed to transmit data concerning the condition of the astronaut and the functioning of his suit.
Mars: Planet for Conquest by Erik Bergaust G.P Putnam’s Sons, 1967