US space agency Nasa is to hold a 'major' press conference on Monday when it is expected to reveal a significant scientific breakthrough.

Speculation is mounting scientsits may reveal they have found liquid water on the planet. If this is the case it is bound to lead to growing optimism about life eventually being discovered.

The agency will gather experts at its HQC in Washington for a briefing where it promises to announce it has solved a 'huge mystery' surrounding the Red Planet.

Experts at this event include Jim Green, the director of planetary science at Nasa and Michael Meyer, lead scientist for the Mars Exploration Program.

One theory is they will announce microbial life on the planet but a more likely scenario is evidence of flowing water.

Those hopes have been given a boost by the attendance of scientist Lujendra Ojha, of the Georgia Institute of Technology in Atlanta, at the Nasa announcement.

He first came up with the theory that Mars has liquid salt water flowing through it during warmer months.