In hindsight we know these quarantine measures were unnecessary - Neil, Buzz, Mike and all other other Apollo astronauts returned from the moon in perfectly good health, and the quarantine was eliminated after Apollo 14. But over lunch with my fellow SpaceX financial analysts a few weeks ago, I posed the question: "what do you think NASA would've done if the Apollo 11 crew came down with horrific symptoms from some mystery moon bug and died right there in quarantine? How in the world would NASA properly dispose of the remains while guaranteeing containment?" Who knows, maybe NASA would've dedicated a rocket launch just to blast the contaminated MQF back into space and away from everyone else! If you have any thoughts, share in the comments because I'm curious to know - I tried researching online but found nothing!

Apollo 12 crew in the MQF - check out Alan Bean (a Texas Longhorn just like me!) giving a Hook 'em Horns after returning from the moon! \m/

Though the moon landings are over (for now!), interplanetary contamination is still an important concern for our robotic probes. There are in fact two types: forward contamination, where we unwittingly transport Earth microbes on our spacecraft that contaminate other celestial bodies, and backward contamination, where hypothetical alien organisms are accidentally brought back to Earth. To prevent contamination, the Committee on Space Research (COSPAR) established by the 1967 Outer Space Treaty sets strict planetary protection guidelines. The stringency of the requirements range from Category I-V as follows, depending on the mission (there are in fact subcategories, click here for more detail):

• Category I: Destinations highly unlikely to harbor life (i.e. the Sun or Mercury)
• Category II: Destinations of interest in the evolution and search for life, but unlikely to be compromised by contamination (i.e. the Moon, Venus, comets)
• Category III: Flyby and orbiter missions to destinations of high interest in the evolution and search for life (i.e. Mars, Europa, Enceladus)
• Category IV: Landers to the same destinations as Category III
• Category V: Sample return missions from the same destinations as Category III & IV

Examples of precautions taken to meet these requirements include intense sterilization of spacecraft components prior to launch or contingency plans to safely dispose of the spacecraft, either due to malfunction or end of mission. Thus far no mission has fallen under Category V, but that will hopefully change in the next few decades as both robotic sample return and crewed missions to Mars take shape!

In an example of planetary protection, at the end of its mission the Cassini probe used the last of its fuel to intentionally crash into Saturn so that it wouldn't accidentally collide with Titan or some other potentially life-harboring moon

But to conclude and circle back to our original point about the horrors of an alien coronavirus - while these safeguards against backward contamination are undoubtedly prudent and necessary, the likelihood of an extraterrestrial pandemic exterminating humanity is exceedingly low. Infection occurs when a pathogen successfully binds to a cell's surface; the only reason bacteria and viruses infect humans is because we've coexisted and evolved together for billions of years. And even then, the likelihood of pathogenicity is minuscule - of the gazillions of known bacteria species, only a couple hundred happen to produce the proteins and other toxins capable of binding to our cells and making us sick. Alien organisms simply would not have this intimacy - their contagiousness and our immune systems would never do battle. Lucky for us, they'd simply be two microscopic ships passing in the night

Is this diagram unsettling? Really it should put you at ease - a nice reminder that Earth's pathogens are the only ones you'll ever have to fight!