Mars has fascinated mankind for centuries with its occasional brilliant appearance in the night sky as a ruddy star. It is the only planet where a solid surface can be clearly seen with a telescope and changes in its polar ice caps, clouds, dust storms, and dusky surface features can be observed. These changes have made Mars known for its seasons like Earth and generated the thought that life could exist. Over a century ago canals were seen on Mars and the theory was that a dying civilization built them to irrigate their crops. The canals were an optical illusion but intelligent life on Mars was so well ingrained in the minds of Earthlings that a radio broadcast of Martians attacking Earth called "War of the Worlds" in 1938 was taken seriously by many and caused panic. Ideas die hard, but the Space Age delivered a fatal blow, at least briefly.
Mariner 4 was the first spacecraft ever to fly past Mars on July 14, 1965 and revealed a dry, cratered, desolate world as dead as the Moon. Gone was the romance of canals and Martians. Mars was a lifeless dust bowl, but Mariner 9 arrived on November 14, 1971 and went into orbit during a historic, global dust storm. As soon as the dust settled, a living planet was revealed to the surprise of everyone. Mars has towering volcanoes higher than any on Earth and a canyon so long that it spans the entire length of the United States. Dried-up drainage channels were seen and there was evidence that water may have at one time existed on Mars. Where there was water, there may have been life, so Vikings 1 & 2 landed on Mars during the summer of 1976. Unfortunately neither lander found any evidence of life, past or present. A new era in the exploration of Mars began on July 4, 1997 when Pathfinder landed with the Sojourner Rover. From that point forward, Mars was invaded by Earthlings - well, actually their machines. Mars Global Surveyor, Odyssey, Mars Express, the Spirit and Opportunity rovers, Mars Reconnaissance Orbiter, Phoenix, and the mighty Curiosity Rover have been or are currently busy exploring and discovering. It does not stop here as the aggressive exploration is going to continue well into the 2020s.
First up is the recent arrival of MAVEN, the Mars Atmospheric and Volatile Evolution Mission that was approved on September 15, 2008. This robust orbiter costs $485 million and its goal is to literally skim, like a surfer, the upper atmosphere of Mars to determine how the atmosphere evolves and how it is being lost. It will collect data and focus on how volatiles such as carbon dioxide, nitrogen, and water are being lost over time, the state of the atmosphere and ionosphere and its interactions with the solar wind, the current escape rates of specific gases to space and its cause, and determine the ratio of stable isotopes in the Martian atmosphere. Scientists will be able to extrapolate the data to see how much atmosphere has been lost. MAVEN will also try and determine the source of the fleeting gas, methane. It is not stable and can only be produced by either volcanoes or life. MAVEN may also act as a relay satellite for landers and rovers for years to come. India's Mars Orbiter Mission has also just arrived and will study the surface features, morphology, mineralogy, and the atmosphere.
Next up is the ExoMars Orbiter/EDM Mission, better known as the Trace Gas Orbiter (TGO) that is being developed by the European Space Agency (ESA). It is a joint project with Russia (Roscosmos) providing the rocket to launch it on January 7, 2016. The main objectives of this mission are to search for evidence of methane and other trace atmospheric gases that could be signatures for evidence of active biological or geological processes and to test key technologies for future missions to Mars. The Entry, Descent, and Landing Demonstration Module (EDM) will separate from the orbiter prior to arrival and land on Mars. It will demonstrate the entry, landing, and communication technologies for future landers and rovers. The spacecraft will arrive at Mars on October 19, 2016 and will perform detailed observations of the Martian atmosphere, searching for evidence of gases of possible biological importance such as methane and its byproducts, the location and source of it and other trace gases. The Trace Gas Orbiter will also act as a relay satellite for future landers and rovers.
InSight is a NASA mission that was approved on August 20, 2012 and is a stationary lander that cannot rove. Its primary mission is to use sophisticated instruments to probe deep beneath the surface of Mars and measure seismic activity, heat flow, and the wobble of Mars on its axis. Mars is smaller than Earth and has less geological activity with no plate tectonics, although it has towering volcanoes that have long since been inactive. No other mission has looked beneath the surface so InSight will have much to reveal. This mission is budgeted at $425 million, will launch on March 8, 2016 and land on September 20, 2016. Landing will occur in a volcanic lowland called Elysium Planitia. It is expected to operate for at least two years.
ESA follows up with its first rover mission to Mars under its ExoMars program. This is another joint mission with Roscosmos where Russia will provide the rocket to launch it and the landing platform. ESA is developing the rover and will operate it. It will use a rocket-powered descent using the Russian landing platform and will egress from it after landing. It will land at a site with a high potential for finding well-preserved organic material. It will determine the physical and chemical properties of the samples, mainly from underground. It may have a better chance of finding a record of past or present biological activities since the atmosphere is too thin to protect the surface from harmful radiation, but anything beneath the surface is better protected. A drill will penetrate to a depth of up to six feet and an onboard laboratory will analyze the sample. The rover will use solar panels to power it for at least two years and will be equipped with cameras - a fully dedicated exobiology rover. It is scheduled for launch in April 2018 and will land during January 2019. The landing site has not been selected.
The last of the approved missions is another Curiosity-class rover that was approved on December 4, 2012. NASA will launch it during late July-early August 2020 and it will land during March 2021. This mission will cost $1.5 billion and is $1 billion less than Curiosity because it will use existing tried-and-true hardware and technology from the Curiosity design. This will keep the cost down and the rover will also use a sky crane for landing. The site selection might be one that was turned down for the original Curiosity mission. The rover will be almost like Curiosity, especially in size and shape, but may include the capability to cache samples for a future sample return mission. The rover will also run on nuclear power, so it will hopefully last the entire decade, which could lead up to the long-awaited sample return mission. Unlike Curiosity, the cost of this rover must be kept within budget or it will be canceled.
Mars has been the focus of attention for exploration and rightly so. It is the only planet benign enough where life may have existed and for astronauts to explore and colonize. In spite of its attraction there are many scientists upset over the favoritism towards Mars while there are so many other exciting and important places to explore. The underground ocean and geysers of Europa, Titan's methane-ethane seas, and the geysers on Enceladus and Triton all command follow-up missions. Venus is crucial for our understanding on global warming and climate change, but it is totally ignored. Uranus and Neptune are totally forgotten as orbiter missions are planned and scrapped almost yearly. Sadly, funding is limited in a world of faltering economies and tight budgets, but at least the future exploration of Mars remains healthy, for now.