Nasa is looking to appoint a new planetary protection officer (PPO), whose main job will be to safeguard the Earth from alien life.

According to the job opening posted on the US Office of Personnel Management website, the PPO will be responsible for avoiding ‘organic-constituent and biological contamination in human and robotic space exploration'.

Biological contamination could happen through two ways, namely through spacecraft returning to Earth and its biosphere, and vice-versa.

The advertisement was posted on 13 July but drew attention only after it was posted on social media.

"The PPO will be responsible for avoiding ‘organic-constituent and biological contamination in human and robotic space exploration'."

US citizens with a degree in physical science, engineering or mathematics can apply for the newly opened position, which offers an annual salary between $124,406 and $187,000 and requires frequent travel. The candidate would also need to have experience in 'space programmes of national significance'.

Applications for the three-year position will be accepted only until mid-August. The term of the job could be extended to another two years.

While the advertisement is unusual, the idea is not novel as the United Nations treaty on space exploration in 1967 urged nations undertaking space ventures to take precautions to protect the Earth from contaminants if found elsewhere.

Current PPO Catherine Conley said in 2014 that humans travelling to Mars could pollute the planet if they died there and it is essential that other planets remain in their natural state, reported Scientific American.