When NASA posted a job description for its "planetary protection officer" role, the space agency was fishing for candidates with advanced degrees and experience working on interplanetary missions.

What it did not expect, however, was an earnest letter from nine-year-old Jack Davis: a fourth-grader who wrote the space agency asking if he could apply.

The new job opening, which Business Insider first publicized in a story on Tuesday, pays up to $187,000 and is for NASA's one and only full-time planetary protection officer — a role established in 1967.

The role is not only responsible for protecting alien worlds like Europa (an icy, ocean-hiding, and potentially habitable moon of Jupiter) from germs on human-launched spacecraft, but also defending the Earth from contamination by alien microbes.

But enamored by the possibilities, Davis — a self-described "Guardian of the Galaxy" — summoned the courage to write and address a letter to NASA on Thursday.

A nine-year-old's letter to NASA asking to apply to be a planetary protection officer. NASA

The full text of Davis' letter, which NASA posted in a press release on Friday, reads:

"Dear NASA,

My name is Jack Davis and I would like to apply for the planetary protection officer job. I may be nine but I think I would be fit for the job. One of the reasons is my sister says I am an alien. Also, I have seen almost all the space movies and alien movies I can see. I have also seen the show Marvel Agents of Shield and hope to see the movie Men in Black. I am great at vidieo [sic] games. I am young, so I can learn to think like an alien.

Sincerely,

Jack Davis

Guardian of the Galaxy

Fourth Grade"

The space agency could have easily dismissed the letter with a chuckle, but planetary science director Jim Green decided to type, sign, and mail a note back to Davis.

Here's a screenshot of Green's letter:

NASA's response to a nine-year-old's application to be a planetary protection officer. NASA

The full text reads:

"Dear Jack,

I hear you are a 'Guardian of the Galaxy' and that you're interested in being a NASA Plantary Protection Officer. That's great!

Our Plantary Protection Officer position is really cool and is very important work. It's about protecting Earth from tiny microbes when we bring back samples from the Moon, asteroids and Mars. It's also about protecting other planets and moons from our germs as we responsibly explore the Solar System.

We are always looking for bright future scientists and engineers to help us, so I hope you will study hard and do well in school. We hope to see you here at NASA one of these days!

Sincerely,

Dr. James L. Green

Director, Planetary Science Division"

The space agency didn't stop there, however.

Jonathan Rall — NASA's planetary research director — also rang up Davis "to congratulate him on his interest in the position," NASA said in the release.

"Although the Planetary Protection Officer position may not be in real-life what the title conjures up, it does play an important role in promoting the responsible exploration of our solar system by preventing microbial contamination of other planets and our own," NASA added.

NASA is accepting applications at USAJobs.gov from July 13 through August 14.

Read our full story about the gig here.