Mariner 4 was the first spacecraft to flyby Mars and the first craft to transmit images of another planet back to Earth
Mariner 4 was the first spacecraft to fly over Mars and the first to take detailed images of the red planet.
The blurry images of craters and bare ground led scientists to believe that Mars looks a lot like the Moon. The photos also immediately made it clear that Mars is not a place for life.
Despite this, NASA sent new scouts to Mars because Mariner 4 had only been able to photograph a small portion of the surface. Subsequent missions showed that Mars is very different from the Moon, that there is an active weather system on Mars, and that the planet has been much wetter in the distant past.
March for Mariner's Visit 4
It's hard to say when the discussions about life on Mars got serious, but it must have been sometime in the late 1800s/early twentieth century when new observations by astronomers sparked a sharp rise in interest in the planet.
American astronomer Percival Lowell studied the planet from his observatory in Flagstaff for years. He made drawings and published them. The resolving power of telescopes was not that great at the time, but Lowell believed he saw channels on the planet that may have been created by intelligent beings.
When his observations became known to the general public, it led to a veritable Mars boom. Books, movies, and television programs about alien civilizations appeared.
On the way to Mars
NASA had its own reasons for going to Mars. The increasing interest in exobiology led people to want to study the possibilities of life on other worlds. At that time, the first discussions arose about avoiding contact in order not to disturb possible life through human research.
Scientists couldn't see a lot of detail through their telescopes. A more detailed picture was needed to make a judgment about the Martian environment before conclusions could be drawn. Initially, NASA wanted to place a lander on Mars, but that idea was abandoned in 1962 when it was discovered that the required Centaur rocket stage would not be ready for the mission planned in 1964.
It was still in the early days of space travel where something repeatedly went wrong. The United States and the Soviet Union tested new techniques on the assembly line. NASA decided to send two probes to Mars that would depart at about the same time: Mariner 3 and Mariner 4. This had worked before when Mariner 1 and Mariner 2 were sent to Venus. Mariner 1's mission failed but Mariner 2 achieved its goal.
Mariner 3 was launched on November 5, 1964. The scout reached space but then things went wrong. The mission was over before it had properly begun. All that remained was Mariner 4. The detected design errors in Mariner 3 were corrected in three weeks and mariner 4 was launched on 28 November 1964. The 260-kilogram spacecraft took more than seven months to reach the red planet.
Mariner 4 reached Mars on July 14, 1965 and had just under 25 minutes to make its observations. In that short time, 21 photos were taken and sent to Earth a day later. They were the first photos sent from another planet.
Mariner 4 flew at a distance of 10,000 to 17,000 kilometers above Mars. That distance was far too great to distinguish life as planets and animals, but small enough to confirm the existence of channels.
After the photos were sent back, it was found that there were no signs of canals or life. By today's standards, the images were out of focus but clear enough to show a heavily cratered surface. Scientists stated that Mars was more like the Moon than Earth.
So there were no channels to be seen, but a lot of craters that varied in size between 5 and 120 kilometers. Scientists suggested that these craters must be 2 to 5 billion years old, similar to the craters on the Moon. They also suggested that Mars' atmosphere would have to be very thin to keep the craters as they are visible all along.
The few photos of Mars did not show Earth features such as mountains and valleys. Later on, new space missions showed them and we were shown pictures of large volcanoes and of Valles Marineris. Valles Marineris is a huge valley that is many times larger than the Grand Canyon in the United States.
Responses to Mariner 4 Results
According to NASA, the results of the Mariner 4 forced exobiologists to accept that life on Mars is not very likely. That was a big disappointment to some and certainly to the general public. However, there was a great deal of uncertainty as only a small portion of the planet had been photographed and the Mariner 4's visit to Mars had lasted less than half an hour.
NASA continued to explore Mars. The next major mission to the red planet was the Mariner 9, which showed a much more varied planet.
The later Spirit, Opportunity and Curiosity rovers have found evidence of water in the distant past, and the observations of these Mars cars have greatly contributed to the images we have taken from space of the red planet.
We still don't know if there was ever life on Mars. The biggest lessons from Mariner 4 are that we shouldn't jump to conclusions. It will be some time before we definitively know whether life ever existed on the red planet.
First published: February 11, 2017
Source: space.com
Comments