NASA should err on the side of caution in ensuring its first dedicated mission to Europa does not contaminate the icy moon of Jupiter with terrestrial organisms, a new report recommends.

The report, prepared by the National Research Council for NASA, recommends that the American space agency shoot for a less than one-in-10,000 chance of one of its spacecraft ferrying even a single organism to the ocean scientists believe lies beneath the jovian moons ice.

The panel split however, with majority and minority opinions, on what specific planetary protective measures are appropriate for a Europa-bound spacecraft.

A majority of the panel endorsed a more conservative approach that could add 10 percent to the missions $250 million price tag.

The two minority views argued either that current protection policy suffices or that there is a slim chance any terrestrial bug could reproduce and flourish even if the craft transported it to Europa's surface.

"Its one of the more likely places in our solar system where you might find life," said Andrew Cheng, another task-force member and the project scientist on the Near Earth Asteroid Rendezvous mission.

However, in designing spacecraft to venture to Europa, NASA wants to take pains to avoid contaminating the moon with earthly organisms, which could compromise future scientific studies or conceivably harm any europan life forms.

Complicating the matter are uncertainties about Europas environment -- including its elevated levels of natural radiation -- and how hospitable it would be to any terrestrial stowaways. Furthermore, recent studies have uncovered a multitude of organisms, called extremophiles, here on Earth that seem to thrive in the most adverse of environments.

Although the Europa Orbiter is, as its name suggests, an orbiting spacecraft, the gradual decay of its orbit means that it would one day impact the moons surface. (The same is the case with NASAs Galileo spacecraft, now in orbit around Jupiter. NASA will likely send that spacecraft crashing into Jupiter when its mission concludes to avoid the possibility it could hit Europa, even decades in the future.)

Without proper cleaning, the wreckage of a Europa Orbiter could contain a multitude of tiny terrestrial organisms that may conceivably contaminate not only the immediate crash zone but also the entire moon, if they were to come into contact with liquid water.

"The disagreement is really, How much is enough?" Cheng said of the disagreement over how clean the orbiter should be. "You dont want to impose such stringent requirements you cant go at all."

The majority view advocated de facto sterilization of the spacecraft, where it would be cleaned prior to launch with alcohol or some sort of sporicide, dry heat or perhaps hydrogen peroxide. The spacecrafts final sterilization would come about thanks to the extreme radiation environment that surrounds Jupiter.

John Rummel, NASAs planetary protection officer, said he sided with the majority view.

"I dont think any other choice is responsible," Rummel said. "In the history of human exploration, very little attention has been paid to this issue. Now we are in a position to do it and to do it effectively and to explore the solar system in a responsible manner."