Sciency Words: Planetary Protection

Today’s post is part of a special series that first appeared on Planet Pailly. Every week, we take a look at a new and interesting scientific term to help us all expand our scientific vocabularies together. Today’s term is:


I swear this isn’t science fiction. The Office of Planetary Protection is a real department at NASA which follows the guidelines set by COSPAR, an international council with jurisdiction over the safe and responsible exploration of space.

The three core tenets of planetary protection are:

  • Don’t contaminate other worlds (we don’t want to harm alien life, if it exists).
  • Seriously, don’t contaminate other worlds (it would suck if the “alien life” we discover on Mars turns out to be E. coli).
  • While you’re at it, don’t contaminate Earth either (have you seen theAndromeda Strain?).

Under COSPAR rules, different mission categories require different levels of planetary protection. Categories I, II, and III require only minimal precautions. Nobody cares if we contaminate Venus. Nothing lives on Venus (probably). Category VI covers missions on the surfaces of worlds that could theoretically support life, and category V is for sample return missions that could theoretically bring alien organisms back to Earth.

Until recently, planetary protection has been a fairly esoteric concern. But now we know there’s water on Mars, and scientists really, really want to get a closer look at that!


The Curiosity rover is currently located near a potential recurring slope line (RSL) site, meaning it’s only a few kilometers from what appears to be actively flowing water. But NASA won’t allow Curiosity to investigate.

First off, I should mention there is a logistical concern. Remember the slope part of recurring slope linea. The slope may be too steep for Curiosity to climb.

But the bigger issue is planetary protection (I mean, we could let Curiosity at least try to climb that hill). Under current planetary protection rules, the exploration of an RSL zone is a category IV mission. Specifically, it’s a category IVc. Curiosity is only rated for category IVb, because at the time of launch no one knew there was water on the surface of Mars. So there is a chance—a remote chance, but a chance nonetheless—that it is carrying live bacteria from Earth.

In my opinion, Curiosity should be allowed to investigate the RSL site anyway. It would be a miracle if any microorganism from Earth could survive on Mars. There’s too much radiation, and the water is brimming with toxic perchlorate salts. And the idea that organisms from cushy, comfortable Earth might outcompete native Martian life forms—life forms that are perfectly adapted to the harsh environment found on Mars—sounds 100% preposterous to me.


At the same time, I know any evidence of life Curiosity might find would be justifiably suspect. We could never rule out the possibility of a contaminated sample.

So what do you think? Should Curiosity keep its distance from potential RSLs, or are COSPAR and the Office of Planetary Protection being over-precautious?


The Office of Planetary Protection (official website).

COSPAR Planetary Protection Policy from COSPAR and the IAU.

Water on Mars: NASA Faces Contamination Dilemma over Future Investigations from The Guardian.

  • John H Reiher Jr

    So how do you sterilize a probe and make sure it stays sterilized? Especially against such sturdy critters like the Tardigrade?

    • Paulo R. Mendes

      Gamma rays?

      • John H Reiher Jr

        Well, according to the wiki page, they can take up to 1,000 times more radiation than most life. So we’d have to hit them with 5,000 to 6,000 Gy to kill them off. Sadly, electronics can only take 50 Gy before becoming damaged. We’d have to build the probe out of unique stuff to stand up to being sterilized.

        Luckily, the manufacturing process is such that I doubt the hardier life forms on earth would survive. I think. The entire manufacturing process would have to be in ultra sterile conditions to completely eliminate any threat of contamination.

        • Paulo R. Mendes

          Holy hell! are you sure that those Tardigrades are not related in any way with the aliens of Independence Day: Resurgence??? o.O’

          • yeah, the sturdiness pf tardigrades make cockroaches look easier to break than promises

    • you dont.

  • Leonardo Faria

    Lieutenant Ripley would say “Penicilline the entire site from orbit. It’s the only way to be sure”.

  • John H Reiher Jr

    Decided what does NASA consider a sterile environment. To reduce the chance of contamination, they have several procedures and protocols for every stage of probe construction. Their website lists what they consider the minimum for their purposes.

  • you wouldnt mind if I made a request would you? I’m writing a steampunk story set far in the future in which humans have migrated to cities above the clouds, however, I need an explanation for how crops grow, how people are able to breathe (pressurised complexes are too sterile for the kind of story I’m trying to make) and why there arent massive epidemics of cancerous tumours from the continuous exposure to radiation

    • Kirov

      Floating cities dedicated to agriculture? And just how high up are they? Oxygen masks should be fine as long as its not too high. I’m not sure about the radiation though. Is it absolutely necessary that there aren’t outbreaks of cancer? Its not like it would kill people right away before anything interesting happened, and it could add to a gritty steampunk atmosphere.

      • assuming that not much changes when it comes to where our clouds happen to be, I’d say about an average of 30000 feet, of course, it’s meant to be soft sf, based more on the characters than the science, but I still want some semblence of reality to be there, I suppose that the outbreaks of cancer could be called something like “the sun plague” or something along those lines, but mainly, the story is going to be episodical (kind of) and about a crew that have been forced out of their city, due to a war that was sparked when a spy was caught stealing plans for aeroplanes (the idea is that humans have regressed back into airships, so, whoever gets planes first rules the world, especially considering that air travel would naturally be the main mode of transportation)

        • Kirov

 This article has a handy graphic chart that I’ve used before. It may or may not suite your needs, as there are a lot of other factors that could come into play, especially with sci fi, but it worked for me. Sounds like you’re cooking up some good ideas, good luck!

          • thanks kirov, I promise to give you one of the first drafts of part (or “episode”) one

          • okay Kirov, I have almost all of my pilot done and all but the last paragraph has been edited by a good friend of mine, so, without further ado:

            The Flight of the Golden Zephyr

            Suspended above the endless expanse of smog and cloud dubbed the Sea of Wind. A city was suspended, a beacon of golden light stood, or, more appropriately, floated, in the pale half-light of the moon. At the very centre of this city, on the uppermost section of an enormous tower if one was to look very closely, they would notice a shadow clambering inside from the rooftop…

            Aaron slipped noiselessly onto the carpeted floor, removed a black facemask and crept slowly toward a table positioned in the centre of the room. On it, bathed in the orange glow of a single guttering candle; a parchment with carefully drawn, labelled images had been placed. Aaron pulled off a black glove and touched the ink images, smiled when they didn’t smudge, rolled up the parchment, and felt the cold, sharp blade press against his neck ‘Bugger…’

            That was three days ago, and, as is customary with these situations, relations had become exponentially worse between the Aetherial Empire and the Republic of Solexia. A spy had been sent to retrieve schematics for a powerful war machine which, in the hands of the Solexians, would surely mean the destruction of the empire. Unfortunately, the spy was caught, and now, a diplomat had to be sent to smooth things over. For Lawrence Colbert, this meant a long, uncomfortable journey by airship across the sea of winds, followed by negotiations that will undoubtedly fail, and, once again, result in another long, uncomfortable journey back. At least, under normal circumstances, but Lawrence definitely didn’t expect to be travelling in this.

            The hull was made of varnished mahogany, with wooden railings trimmed tastefully with brass, plated onto the wooden hull in golden lettering, the name of the ship was displayed proudly “the Golden Zephyr”

            ‘Pretty impressive, isn’t she?’ The voice belonged to a black haired young man in a crimson coat and brass goggles. ‘She certainly is a sight to behold’ said Lawrence ‘I suppose I should get my things on board’ he continued, gesturing to a brown leather travelling trunk. ‘Ah’ said the young man, understanding beginning to dawn,

            ‘You’re the diplomat aren’t you?’ Lawrence smiled

            ‘Yes, yes I am’ he began

            ‘I’m sorry but I’m afraid I haven’t caught your name, you wouldn’t mine me asking would you?’ the boy grinned.

            ‘Lucas’ he said

            ‘But most people here just call me captain.’

            Aaron Berkeley stared upwards at the ceiling, the warm orange glow of the sunrise shining on his face from the tiny barred window at the top of the wall. ‘WAKEY WAKEY YOU MISERABLE LITTLE BASTARDS!’ the voice of the guard boomed through the stone walls of the prison cells as he bashed a metal ladle against the irons bars of the cells, stopping at Aaron’s cell. Before the guard could react, a hand shot out of the cell, grabbed him by the collar, twisted him the other way and slammed his back against the door, changing its grip so that the guard was now being held against the bars by an arm outstretched across his chest and holding onto his shoulder. This was soon followed by a second hand taking hold of the guards head and jerking it violently to the left, creating an unmistakable snapping sound that echoed throughout the halls. The corpse of the jailor fell to the ground, his neck limp and his eyes glazed over.

            No-one had noticed the pale blonde man clad in a black suit step out of the prison. The guards were too busy searching for the escaped prisoner, and you can get into a lot of trouble if you disturb an important looking man like that…

            The rather unlikely group of travelling companions were sat at the captains desk, which, by the looks of things, had paperwork organised in the “availably surface” method of storage, mountainous stacks of paper had been cleared, and the waste-paper basket was noticeably more full, all that had survived the dreadful scourge of paperwork was two ornate sheets of paper, with dotted lines for signage.

            ‘Well’ Lucas, began, his deep blue, and above all piercing blue eyes greatly contrasting with the pale, youthful visage.

            ‘Spymaster… Helena?’ the slim, red haired woman sat beside Lawrence nodded softly, not a single muscle seemed to move on her face

            ‘And sir Lawrence Colbert, Duke of Zephyr?’

            ‘Yes’ Lawrence replied.

            ‘Okay, Helena, I’ll just need you to sign here.’ Lucas pushed one of the sheets toward the silent woman who, if Lawrence was one to judge, absolutely terrified him.

            ‘and, you, your grace, will need to sign this one, just so everything’s on record’ His Grace, Duke of Zephyr snapped a silver pen with golden scrollwork decorations out of his pocket and scribbled a signature down onto the contract, taking care not to read a single word of the contract, lest the Latin conjure up memories of school.

            ‘Wonderful’ Lucas said, in a state of anti-wonderment

            ‘I’ll just show you to your staterooms shall I?’

            • oh, by the way, a lot of those new paragraphs are actually new lines of dialogue, Microsoft Word is a finicky little bastard

            • Kirov

              Great start! I’m looking forward to seeing some more submitted to the site. I would recommend going over it again with a fine-tooth comb for grammar, and as far as the story, I think you could make it even better by expanding on the scenes you currently have. I also tend to like setting up my stories by explaining how the world you’ve created works, but that’s my personal preference. Some readers don’t like reading about the worldbuilding and just prefer the story. But awesome work!

            • thanks, as I’ve said, it’s still in the early development stages, so far I haven’t even got the call to adventure yet, but I am working on it!

            • oh, by the way, I actually did a bit of research, it turns out that what I am writing is more of an edisonade/steampunk fusion due to the travelling element, by the way, I need suggestions for how pilots navigate across an almost landmark-proof landscape

            • Kirov

              If instruments are a thing in your universe, pilots (at least in the military) are tested on whether they can fly without visibility, using airspeed, direction, timer, and a map. Given that you have airships, any sort of sea based navigation should work just as well in the upper atmosphere: compasses, sextants, and positions of celestial bodies.

            • hmm, I suppose that could work at one point I had an idea for a submergible airship that goes down below the clouds to get it’s bearings, that of course lead to the idea of “sub-aether” military ships, but that conflicted with a future part of the plot