Despite a rigorous scrubbing before its launch, NASA's Mars rover Curiosity arrived at the Red Planet with plenty of bugs aboard: 377 strains of 65 Earthly bacteria species, an analysis shows.

After that cleaning and before it was blasted off on its journey to mars, scientists swabbed down the surface of the automobile-sized Curiosity to determine what bacteria might have evaded the spacecraft's "face wash."

Of the various bacteria identified in the first analysis conducted on the swabs, a few would likely have been able to survive the cosmic voyage to land with the rover in August 2012, researchers report in Nature News.

Mostly of them are from the genus Bacillus, and samples swabbed from the rover were subjected to a simulated trip to the Red Planet, undergoing drying, temperature extremes, changes in acidity and ultraviolet exposure, the researchers said.

Of the identified strains, almost 11 percent where able to survive at least some of those extreme laboratory conditions, suggesting they might still be alive on Mars, said scientists at the University of Idaho, where the voyage to Mars was recreated.

There have been concerns that the cleaning process on Curiosity before its launch was not as rigorous as guidelines call for, and the discovery of so many varieties of microorganisms seems to bear this out, the researchers said.

"When we embarked on these studies there wasn't anything known about the organisms in this collection," says UI microbiologist and lead study author Stephanie Smith.

Contamination of any spacecraft sent to worlds beyond Earth could compromise explorations there, the researchers said.

"This study will help gauge whether microorganisms from Earth pose a forward contamination risk that could impact future life detection and sample return missions," the authors wrote.

The study will help identify the hardiest of organisms that might be present on a spacecraft and could lead to development of cleaning and sterilization technologies to prevent such contamination.

Although some of the bacteria survived the experiments here on Earth, it cannot be known if they are still alive on Curiosity to possibly contaminate its science researches.

"We don't know yet if there's really a threat," says Smith. "Until we know, it's important to take a precautionary approach."

The University of Idaho researchers were joined in the study by scientists from NASA's Jet Propulsion Laboratory in Pasadena, California, Idaho State University, Colby College in Maine and the South Dakota School of Mines and Technology.

The study findings were presented at the annual meeting of the American Society of Microbiology in Boston.