At 3.32pm on Monday August 6, over a hundred people in the Museum’s Coles Theatre erupted in cheers as word came through on the live feed that we were watching from the mission control room at NASA’s Jet Propulsion Laboratory (JPL) in California that NASA’s latest Mars explorer, the Curiosity rover, had landed safely.
During our public program for the landing, I was surprised to discover how many visitors thought that Curiosity was the first spacecraft to land on Mars. In fact, this rover is only the latest in a series of Mars landing programs, stretching back 40 years, so I think that before writing more about Curiosity and the Mars Science Laboratory program, it would be timely to devote this blog post to a little bit of history about Mars landing missions.
It was 1971, when the Soviet Union’s Mars 3 made the first successful touchdown on the Martian surface (after the failure of its twin Mars 2). Unfortunately for Mars 3, it landed in the middle of a raging dust storm, which was probably responsible for it ceasing to transmit after about 15 seconds, with only part of an image sent back to Earth. The demise of the lander meant that the tiny PROP-M rover it carried, which would have been the first mobile Mars explorer, was not deployed.
The Museum’s collection includes a 1:2 scale model of the Mars 3 spacecraft, which was formerly on display in the Space: beyond this world exhibition. Originally on loan from the USSR Academy of Sciences, this model was purchased by the museum in 1995, along with a number of other examples of Soviet space hardware. The model shows Mars 3 in its interplanetary cruise configuration with the lander tucked under the conical atmospheric entry heatshield at the top of the orbiter.
NASA’s first Mars landing program was Viking, which successfully landed the twin Viking 1 and 2 spacecraft in July and September, respectively, 1976. As landers, rather than rovers, the Viking could only explore the environment of their immediate surroundings, so NASA targeted them for different parts of Mars to sample two different surface environments. Viking 1 sent back the first colour images from the Martian surface and the two spacecraft provided a wealth of images and scientific data from the planet until they ceased to operate in the early 1980s. Both Viking landers carried a biology experiment to look for evidence of possible microbial life on Mars, but the results of this experiment were controversial: many scientists believed that the reactions observed were due to chemical processes in the Martian soil, while others maintain even today that they were the result of biological processes.
It was more than 20 years before another spacecraft landed on Mars. In 1997 NASA’s Mars Pathfinder mission used the airbag landing technique to deliver the first rover to operate on the Martian surface, Sojourner. The first landing mission to occur in the age of the internet, Pathfinder’s live landing broadcast was viewed by approximately 40 million people (including here at the Powerhouse Museum in our first internet-based public program), making it one of the biggest internet events of the day. Although only planned to last for about a month, the Pathfinder lander operated for almost three months, while the Sojourner rover, small by comparison with Curiosity, operated for 83 Martian days, sending back 550 photographs and analysing the chemical properties of rocks and soils at 16 locations near the lander.
The Mars Pathfinder program marked the beginnings of a renewed interest in Mars by NASA, sparked by the discovery of what was thought to be a microbial fossil inside a meteorite from Mars found in Antarctica, known as AH 84001 Since water is necessary for life, and since life is found in even the most extreme watery environments on Earth, the search for life (past or present) on Mars has focussed on looking for environments in which liquid water persisted long enough for microbial life to evolve.
The scientific goal of NASA’s Mars Exploration Rover program, which landed the twin rovers Spirit and Opportunity on Mars in January 2004, was to geologically characterize rocks and soils over as wide an area as possible of the Martian surface, seeking clues to past water activity. Landing on opposite sides the planet, these two sophisticated solar-powered robotic explorers long outlived their initial 90 Martian day primary mission. Spirit, the first to land, covered almost 8 km of travel before becoming stuck in soft soil in May 2009. It continued to function as a stationary science research platform until March 2010, when the onset of Martian winter at its location caused it to shut down for lack of power. Attempts to contact Spirit with the onset of spring were not successful and the spacecraft’s mission was declared ended in May 2011.
Opportunity, however, still continues to explore, having covered more than 34.5km. It traversed from Eagle crater, where it landed, to Victoria crater and arrived at Endeavour crater, named for Captain Cook’s ship, in August 2011. As it continues to explore this region, its data will no doubt complement the finds made by Curiosity in Gale crater.
The most recent successful Mars landing mission prior to Curiosity, was NASA’s Phoenix lander (a follow-on to the failed Mars Polar Lander mission of 1999), which touched down in Mars’ northern polar region in May 2008, to examine the soil and atmospheric conditions at the boundary of the polar ice cap. Phoenix found ice just below the surface of the soil, and more importantly, evidence of perchlorate (ClO4). This chemical can be used for rocket fuel and as a source of oxygen for future colonists: under certain conditions it can also inhibit life. It is possible that perchlorate in the soil at the Viking landing sites may have been responsible for the reactions detected by the life experiments. Operating until November 2008, Phoenix’ mission ended when the onset of winter rendered its solar panels unable to function.
So from the forgoing, it’s clear that, while Curiosity may not be the first spacecraft to land on Mars, it represents the latest step in a succession of increasingly sophisticated robotic explorers. There will be more blog posts about the Curiosity rover in coming weeks as its mission of exploration gets under way in earnest after its ‘shakedown’ period.