Three new studies conducted on the International Space Station show that microbes can survive interplanetary travel.

The study was based on spore-forming bacteria, which can survive harsh environments on earth. These bacteria could hitch a ride on spacecrafts and contaminate other planets, making the hunt for alien organisms difficult.  

The research on ISS shows that the current strategies used to lower the levels of microbes on spacecrafts might be inadequate and that tiny hitchhikers could colonize Mars.

Spores of Bacillus pumilus SAFR-032 are resistant to both UV radiation and hydrogen peroxide treatment. Under extreme conditions, microorganisms develop endospores. These spores help the organism resist the environmental assaults and protect its genetic material.

In one of the experiments, researchers exposed these spores to simulated Mars environment. The team found that these hardy bacteria survived for 30 minutes whereas other bacteria survived for just 30 seconds.

The team then exposed the spores to space conditions by keeping them on the European Technology Exposure Facility (EuTEF), a test facility attached to the ISS.

"After testing exposure to the simulated Mars environment, we wanted to see what would happen in real space, and EuTEF gave us the chance," said Kasthuri J. Venkateswaran, a researcher with the Biotechnology and Planetary Protection Group at NASA's Jet Propulsion Laboratory and a co-author on all three papers, according to a news release. "To our surprise, some of the spores survived for 18 months."

Researchers found that the spores that survived the space ordeal had higher levels of proteins with UV radiation resistance. These organisms, when revived on Earth, showed increased resistance to U.V radiation.

In the second study, spores of Bacillus pumilus SAFR-032 and Bacillus subtilis 168 were exposed to space radiation and temperature fluctuations in the EuTEF for 1.5 years. Some of the bacterial samples were also exposed to simulated Martian environment. However, when researchers filtered out the radiation, around 50 percent of these spores survived. The study shows that bacterial spores can hitch a ride to Mars if they are sheltered against the solar radiation.

The third study was conducted on organisms that live on rocks. These bacteria were kept in the EuTEF test facility for over 1.5 years. Researchers wanted to know whether space rocks could transport life from one planet to another, a theory known as lithopanspermia. The team selected organisms that are known to survive tough conditions on Earth. The duration of the study was short. However, researchers believe that the experiment results provide evidence that hardy organisms could survive in space for millions of years before landing on a planet.

All the three research papers are published in the Astrobiology Journal.