Microbes from Earth pose risk to a pristine Mars

A Belfast-based expert on extreme environments for microbes is helping the US space agency Nasa to study whether Mars could become contaminated with bacteria from Earth.

Space invaders was a popular arcade game but Nasa takes the business of invading microbes very seriously given the damage caused if bacteria from Earth managed to gain a foothold on the red planet.

This is not as far fetched as it might seem, said Dr John Hallsworth of the Queen's University Belfast School of Biological Sciences. He was one of just 22 experts - and the only one from Britain or Ireland - assembled from around the world to look at the risk of cross-planetary contamination.

Satellites and spacecraft are built in clean rooms to eliminate all bacteria but it just doesn’t work. “It is impossible to sterilise them, there are plenty of microbes on them,” he said. The question is if they got up there could they survive.

“We can only understand what living systems can do by understanding life on Earth,” he said.

Bacteria and other organisms have managed to colonise virtually every environment on earth, including the harshest of them. High temperature, low temperature, extreme drought, acid, caustic, earthly bacteria have survived them all.

Nasa brought the group together six months ago to help it identify "special regions" of Mars, places that based on what has been seen on Earth would offer a place where invading microbes could grow, he said. Any area defined as a biological hot spot by the "Special Regions - Science Analysis Group" becomes an exclusion zone for surface landers or manned spacecraft sent by Nasa, Dr Hallsworth said.

Nasa sees two key reasons for being cautious about its planetary protection policy, which assumes anything carried up from Earth could pose a threat, he said. One is the importance of retaining a pristine Martian environment, one untouched by invasive species.

“Say in the past there was life on Mars and there were bits of DNA or any kind of molecule left over we can find. If we contaminate it with present day life we contaminate these samples,” Dr Hallsworth said.

Then there is the possibility of sending humans to live on Mars. They will not need underground water or ice reserves to become infected with bacteria from Earth, he said.

The group considered ways a stowaway microbe might get a foothold. A lander typically fires rockets to slow its descent and this could melt ice crystals in the soil to provide warmth and moisture for the microbe.

The team also considered the crash landing of a lander that produces energy from heat released from radioactivity. It would provide a long term toasty environment, melting ice below the surface to provide a cosy home away from home for any lucky microbes with a one-way ticket to Mars.

The special regions are areas where this could happen spontaneously however, hence Nasa’s concerns. Once installed and reproducing successfully, evolution would take its course, allowing pioneer bacteria to spread out and colonise almost any environment available.

“The Earth isn’t a closed system and microbes move about,” Dr Hallsworth said. The same could hold true for Mars if earthly space invaders managed to land.