May 30,2015 – On May 30, 1971, an Atlas-Centaur vehicle carrying the Mariner 9 spacecraft lifted off from Cape Kennedy’s Launch Complex 36B. Later that year, Mariner 9, which carried an instrument built by the Laboratory for Atmospheric and Space Physics (LASP) in Boulder, would become the first spacecraft to orbit another planet.
Mariner 8 and 9 were designed as complementary missions in NASA’s Mariner series of the 1960s and early 1970s. Both were designed to be the first Mars orbiters, marking a transition in our exploration of the red planet from flying by the planet to spending time in orbit around it.
Mariner 8 was to launch first, but on May 8, 1971, 365 seconds after launch, Mariner 8’s Centaur main engine shut down and the upper stage of the rocket, along with Mariner 8, fell into the Atlantic ocean about 560 km north of Puerto Rico.
Mariner 9 then combined the mission objectives of both Mariner 8 (mapping 70% of the Martian surface) and Mariner 9 (a study of temporal changes in the Martian atmosphere and on the Martian surface). For the survey portion of the mission, the planetary surface was to be mapped with the same resolution as planned for the original mission, although the resolution of pictures of the polar regions would be decreased due to the increased slant range. The variable features experiments were changed from studies of six given areas every five days to studies of smaller regions every 17 days.
Mariner 9 launched 11 days after the U.S.S.R.’s Mars 2, but actually arrived at Mars thirteen days earlier than the Soviet spacecraft. After a journey of more than 600 kilometers, Mariner 9 arrived in Mars orbit on November 14, 1971, becoming the first human-made object to enter orbit around a planet other than Earth.
Mariner 9 was designed to provide the most complete view of Mars ever obtained. Atmospheric structure, composition, density, and pressure were to be analyzed again using techniques similar to those used on previous Mariner Mars missions. Mission goals were to map over 70% of the Martian surface with resolutions ranging from 1 km per pixel to as good as 100 m per pixel during successive Mars orbits from an altitude of about 1,500 km. The spacecraft would also look for signs of volcanic activity denoted by heat anomalies on the surface using infrared radiometry. Mars’ two moons, Phobos and Deimos, were also to be analyzed by Mariner 9.
LASP provided the Ultraviolet Spectrometer (UVS) for the mission, as well as the Ultraviolet Spectrometer Principal Investigator, Charles A. Barth, and Co-Investigators, Charles Hord and Ian Stewart.
The UVS was designed to received UV radiation from the surface and atmosphere of Mars, scan selected bands of this radiation, and provide an intensity value as a function of wavelengths on the basis of scan-cycle time. The scientific objectives of the experiment fell into two broad categories: UV cartography and UV aeronomy.
When Mariner 9 arrived at Mars, there was a huge dust storm obscuring the entire planet. The dust storm had started on September 22, 1971, but quickly grew into one of the largest global storms ever observed on Mars.
Ground controllers sent commands to the spacecraft to wait until the storm had abated and the surface was clearly visible before compiling its global mosaic of high-quality images of the Martian surface.
The storm persisted for a month, but after the dust cleared, Mariner 9 revealed a very different planet than expected – one that boasted gigantic volcanoes and a grand canyon stretching 4,800 kilometers (3,000 miles) across its surface. More surprisingly, the remains of ancient riverbeds were carved in the landscape of this seemingly dry and dusty planet.
Mariner 9 exceeded its primary photographic requirements by photo-mapping more than 80 percent of the planet’s surface at a resolution of 1 to 2 km. The dedicated imaging mission began in late November, but because of the dust storm, photos taken prior to about mid-January 1972 did not show great detail. Once the dust had subsided, Mariner 9 began to return spectacular photos of the deeply pitted Martian landscape. The spacecraft also provided the first closeup pictures of the two small, irregular Martian moons.
By February 1972, the spacecraft had identified about twenty volcanoes, one of which, later named Olympus Mons, dwarfed any similar feature on Earth. Olympus Mons, part of Nix Olympica — a “great volcanic pile” possible formed by the eruption of hot magma from the planet’s interior – is 25 kilometers high and has a base with a diameter of 600 kilometers.
The spacecraft also gathered data on the atmospheric composition, density, pressure, and temperature and also the surface composition, temperature, gravity, and topography of Mars. A total of 54 billion bits of scientific data were returned.
The vast amount of incoming data countered the notion that Mars was geologically inert. Some of the observed features included ancient river beds, craters, massive extinct volcanoes, canyons, layer polar deposits, evidence of wind-driven deposition and erosion of sediments, weather fronts, ice clouds, localized dust storms, morning fogs and more. With evidence of flow features, there was some speculation on the possibility of water having existed on the surface during an earlier period, but the spacecraft data could not provide any conclusive proof.
The results of the Mariner 9 mission paved the way for the Viking program. Confirmation of the atmospheric pressure allowed engineers to design the Viking landers for a safe descent and the images and data retrieved fueled the fire for further Mars exploration. Mariner 9 pictures were later used to select landing sites for the two Viking missions.
After depleting its supply of altitude control gas, Mariner 9 completed its final transmission and was turned off on October 27, 1972. Mariner 9 was left in an orbit which should not decay for at least 50 years, after which the spacecraft will enter the martian atmosphere.