Did You Know?
The first spacecraft to visit Mars was Mariner 4 in 1965.
Mariner 4 was the first spacecraft to fly by Mars, and the first to return close-up images of the Red Planet.
Its blurry views of craters and bare ground led some scientists to think that Mars is similar to the moon. It squashed some views that Mars was a haven for life.
Nevertheless, NASA continued to send spacecraft to Mars because Mariner 4 only took pictures of part of the surface. Later missions showed that Mars is actually quite different from the moon, with an active weather system and a much wetter past.
NASA had its own reasons for going to the Red Planet. The nascent field of exobiology was examining the possibilities of life on other worlds. (And just as vehemently, scientists began invoking their concerns about hurting or disturbing that life through human exploration.)
But scientists could only see so much detail through a telescope. A close-up view would be required to see what the Martian environment was like, before drawing conclusions. NASA originally wanted to have a lander on the planet, but scaled that back in 1962 when planners determined a Centaur rocket stage would not be ready for the planned 1964 mission.
This was the early days of space exploration, with a high rate of failure as NASA and the Soviet Union each tested new technology. As such, NASA elected to send two spacecraft to Mars around the same time – Mariner 3 and Mariner 4. This success had worked previously with Mariner 1 and Mariner 2's voyages to Venus; while Mariner 1 failed, Mariner 2 successfully sent back information.
Mariner 3 launched Nov. 5, 1964. It made it into space successfully, but a fairing intended to protect the spacecraft during launch jammed instead of coming off as planned. This doomed the spacecraft before the mission could get started.
This left only Mariner 4 to carry out the mission. NASA and its contractors hastily redesigned the nose fairing in the three weeks before its launch, and cheered its success when the spacecraft successfully headed for Mars on Nov. 28. The 574-pound (260 kilogram) spacecraft spent more than seven months cruising to the Red Planet.
Mariner 4 spent just 25 minutes doing observations of Mars as it cruised by on July 14, 1965. In that brief time, it took 21 full pictures that it beamed back to Earth the next day. The spacecraft's views would be the first ones beamed back from another planet.
From 6,200 miles to 10,500 miles (10,000 to 17,000 kilometers) up, Mariner 4 was too far away to see life such as plants or animals, NASA cautioned. Still, it would perhaps be close enough to figure out if there were canals or not.