As Nasa prepares to announce the "mystery" behind Mars is solved, ITV News looks back at the previous missions to Mars and what they revealed.
Dozens of missions have been launched to try and gather information about the Red Planet, but the most successful have been in the past 15 years.
Here are ten of the most significant developments in humans' efforts to uncover the secrets of Mars:
- The first close-up photograph of Mars was taken by Mariner 4 in 1965 after an eight month voyage. In the 22 pictures taken, impact craters touched with frost can be seen.
- Nasa’s two rovers, Spirit and Opportunity, were sent to Mars in 2004. Both have provided evidence that water once flowed on the Red Planet. Nasa’s Opportunity discovered rocks containing clay, supporting recent evidence that neutral-pH water could have existed on Mars.
- The Phoenix lander, which arrived on Mars in 2008, found water in the form of ice beneath the surface of the planet.
- The £1.6 billion Curiosity rover arrived in 2012 to search for signs of ancient habitable environments. It discovered a potentially habitable lake and groundwater system dating from about 3.7 billion years ago.
- It also detected surface methane in December 2014. This could point towards there being some kind of life on the planet - almost all the methane on Earth comes from life forms. But by itself, the findings are not enough to show evidence of life.curiousi
- Curiosity discovered in January 2015 that Ancient Mars could have the right chemistry to have supported living microbes. Carbon, hydrogen, oxygen, phosphorous and sulphur (all key ingredients necessary for life) were found by studying many rocks that formed in water.
- Data analysis from Curiosity suggested in 2013 that a catastrophic event destroyed the Red Planet’s atmosphere. About 3.5 billion years ago, Mars and Earth were much more similar, according to Nasa.
- A Colorado study in May 2015 found a mission to Mars would expose astronauts to dangerous levels of radiation, making a journey unlikely.
- Britain made a failed mission to Mars with Beagle 2. It was finally spotted in January 2015 after disappearing 12 yearsago without a trace. It was seen 5km from it’s original touchdown site by scientists operating a camera on Nasa’s Mars Reconnaissance Orbiter.