The Mariner Missions: Venus, Mars, and Mercury

Date: March 16, 1975 A.D.
Author: NASA Scientist

Dear Journal,
     "Mariner 10 has orbited Mercury for the third and final time," were the words from the space center.

     It had been more than a dozen years since Mariner 1 had first set out, only to be purposely destroyed because it veered off course. It's brother Mariner 2 would soon follow and encounter more success. Mariner 2 became the first spacecraft to visit another planet. The excitement that we might find life on Venus was overbearing. The planet had a thick layer of clouds shrouding it in mystery. And there was a theory that the sun had been cooling for thousands of years and as it did, every planet in the world had an era where life rose due to the planet having a habitable temperature. Venus might be just entering this life era. We were curious about what aquatic or amphibious life exited on this enigmatic world.
     Mariner 2 and later Mariner 5 would later cool our speculation. Venus was detected to be very inhospitable to life. This morning and evening star had an average temperature of eight hundred degrees Fahrenheit due to a greenhouse effect caused by the cloud layer. In addition, the atmospheric pressure was about ninety times as great as Earth's. Although life seemed improbable, the mission to Venus was a significant development in itself for journeys are built upon previous expeditions.
When Mariners 6 and 7 zoomed to within nearly two thousand miles of Mars, we were disappointed by the moon-like surface. Where were the canals of Percival Lowell? Then Mariner 9 arrived at the Red Planet. At first, the planet was veiled by a dust storm and the probe was unable to see anything. The storm cleared to reveal gigantic volcanoes hundreds of miles wide, canyons, and other features suggesting that water had existed on the planet at some time. And where there was water, there was a higher possibility of life.
     Finally, Mariner 10 built upon the successes of previous Mariners 2 and 4 and went to Venus again. This trip wasn't like the previous ones however. Mariner 10 flew to Venus and took three thousand pictures, including several interesting features such as a "eye of Venus" where the sun's heats almost always falls directly overhead. Mariner 10 then used Venus's gravity to propel it towards Mercury, where it would orbit three times. At Mercury, Mariner 10 found a planet heavily cratered like the moon, measured a temperature that ranged from eight hundred degrees to negative three hundred degrees Fahrenheit, and detected a weak magnetic field. 
     The inner planets have now been traveled to. The next goal is to journey to the outer planets. NASA is planning a mission called Voyager to flyby Jupiter and Saturn. I can't wait.
     Someday, humans will set foot on another planet after robotic probes have created a good map of the solar system. Instead of Lewis and Clark, we will remember probes like Mariner and Voyager.