A Belfast scientist is to help NASA investigate whether microbes from Earth could contaminate Mars.
There has been increased exploration of the red planet over the last decade and NASA intends to put another lander (unmanned craft) on Mars in 2016.
Scientists are now examining which special regions of the planet could support bacteria from Earth.
Dr John Hallsworth is one of just 22 scientists on the Special Regions-Science Analysis Group (SR-SAG).
He is the only one of the group from Britain or Ireland.
He said there was currently no such thing as a sterile spacecraft and so any that landed on Mars could be a major source of microbial contaminants.
"There has been talk of establishing a human base on Mars and also interest in mining the planet for minerals," Dr Hallsworth said.
"It is therefore important to avoid chemical or microbial contamination of potential resources, such as Martian water or ice.
"No-one has yet proved that there is deep groundwater on Mars, but it is plausible as there is certainly surface ice and atmospheric water vapour, so we wouldn't want to contaminate it and make it unusable by the introduction of micro-organisms."