NASA Mars rover Opportunity found that Mars had life friendly fresh water once. This was confirmed by the scientists at NASA on 23 January 2014. The discovery has reinforced the similar discoveries made by Curiosity on the other side of the planet Mars.
Opportunity had been analyzing water-bearing rocks at the rim of an ancient impact crater called Endeavour. Rather than the chemical fingerprints of acidic, salty water found at previous sites, Opportunity discovered telltale clays called smectites that form in Ph-neutral water.
The finding adds to an emerging picture of a planet Mars that spent its first billion years or so warmer than it is today, with pools of fresh water on its surface. Gradually, water activity declined and what did exist became acidic, scientific findings reveal, and then, beginning about 3 billion years ago, Mars dried up.
By studying rocks at various levels, scientists expect to not only get a better idea of how long the planet Mars was able to sustain life, but where conditions might be favourable to perverse key evidence, such as organic carbon.
NASA Mission on Mars
Opportunity, along with its now-defunct twin, Spirit, landed on Mars in 2003 for concurrent 90-day missions to look for clues of the past existence of water on planet Mars.
NASA in 2012 another Mars rover named Curiosity equipped with an onboard chemistry lab for follow-up investigations to determine that Mars had other ingredients essential for supporting life. Curiosity is exploring an area known as Gale Crater.