This post was inspired by recent media stories about UFOs (now rebranded as UAPs by the Very Serious People) and an episode of Neil Degrasse Tyson's Cosmos: Possible Worlds I watched on a Delta flight. Also this might look like a post about ETs but it's actually about institutional epistemic bias.

Preventing Alien Invasions

One of the job titles at NASA is "Planetary Protection Officer."

Image by Randall Munroe

The job description does not include fighting off aliens with high-concept science-fiction weapons^[1]. The primary responsibility is to prevent Earth's scientific equipment from contaminating other heavenly bodies with microbial life or organic molecules. This is good science: If we find any evidence of life or its chemical precursors in space, we want to be sure that we aren't actually "discovering" stowaways from Earth brought by our own probes. It's also good conservationism: NASA has no desire to mess with possible ecosystems on other planets by introducing new species. The possibility of biological hitchhikers returning through Earth via sample return missions and then harming us is comparatively remote, but appropriate precautions are also taken for these types of missions.

From the NASA webpage about Planetary Protection:

Planetary Protection requirements for each mission and target body are determined based on the scientific advice of the Space Studies Board and on NASA or international policy guidelines. Each mission is categorized according to the type of encounter it will have (e.g., flyby, orbiter or lander) and the nature of its destination (e.g., a planet, moon, comet or asteroid). If the target body has the potential to provide clues about life or prebiotic chemical evolution, a spacecraft going there must meet a higher level of cleanliness and some operating restrictions will be imposed. Spacecraft going to target bodies with the potential to support Earth life must undergo stringent cleaning and sterilization processes and greater operating restrictions.

The episode of Cosmos that I watched mentioned this classification system and piqued my interest, so I read the page. There are five categories. Below are layperson-accessible summaries (based on my understanding) and examples of destination planets that would place missions in a particular category (taken directly from NASA).

• Category I: Missions to bodies absolutely not interesting in terms of possible life or even prebiotic chemistry. Examples: most asteroids and hellish environments like Io.
• Category II: Missions to bodies that could tell us something about chemical evolution or life's origins, but where the mission is not likely to compromise future study. Examples: Venus, Earth's moon, comets, gas giant planets and most of their moons.
  • A special category II* is used for missions to icy satellites where we are concerned about polluting possible liquid-water environments.
• Category III: Applies to fly-by and orbiter missions, where accidentally crashing into the object of study could introduce contaminants and poses a risk to the integrity of future work. Examples: fly-bys of Europa and Enceladus, moons of Jupiter and Saturn respectively that are of particular interest to astrobiologists as possible locations where life could arise.
• Category IV: Same as category III, but for landers and probes that are intentionally brought into physical contact with their targets. So far it seems only Mars missions have fallen in this category, but if anyone were to plan a landing on Enceladus or Europa I think it would be a category IV.
  • There are a few sub-categories for this depending on what kind of experiments are planned or if they travel to "Martian Special Regions" where Martian life is most likely to be and/or Earth life is likely to survive.
• Category V: Category IV-type missions which in addition intend to return to Earth with samples for study. Category V missions can be restricted or unrestricted, referring to how much we have to worry about bringing alien microbes home. Examples: Venus (unrestricted), Mars/Europa/Enceladus (restricted).

What these Categories Mean

From what I can tell, NASA thinks about objects in the solar system in essentially three levels of "interesting", where "interesting" here means "containing extinct or extant life or prebiotic chemistry or evidence thereof."

• Almost definitely not interesting (Category I)
• Very unlikely to be interesting (Category II)
• Possibly interesting (Category III, IV, V)

I first Noticed I Was Confused when Neil Degrasse Tyson's narration of Cosmos explained that Mars, Europa, and Enceladus where all in the "Possibly interesting" grouping. I had two points of confusion.

Confusion 1: Where are the "Interesting" and "Very Interesting" bodies?

The short answer is that, in our solar system at least, they don't exist (other than Earth, which is left out of the categories for obvious reasons). I consider this a deficiency of the classification system: Suppose we landed on Europa tomorrow, drilled under the ice, and discovered a society of tentacled creatures holding a banner that said "Welcome Earthlings!" In this case it would be absolutely critical not to introduce new and potentially harmful life to Europa, but we wouldn't have a new category to distinguish the appropriate amount of caution. We could simply make one, of course, so this doesn't bother me as much as the next confusion. Still, if I were making the categories used by planetary protection, there would be some level for bodies that we definitely know or strongly suspect have extant life, so that we are extremely careful to not to allow contamination in either direction.

Confusion 2: Why is Mars on the same level as Europa and Enceladus?

Previous study of Europa and Enceladus have convinced NASA that both contain large, subs-surface bodies of liquid water, and likely also have hydrothermal vents. Mars, from what we know, most likely has neither (though could have in its past). I'm no astrobiologist, but since hydrothermal vents have been described as ideal conditions for the origin of life, and liquid water is critical for all forms of life as we know it, I consider the origin and present existence of life in our solar system to be much more likely on either of these moons than on Mars. So wouldn't it be appropriate to be more cautious for (as of now hypothetical) missions to Europa and Enceladus?

I'll admit the answer to this question could plausibly be "no." I see two ways this is possible:

1. I could be wrong about Mars being less interesting. (Update: A comment from JPL employee noborny provides an argument why this is the case)
2. It could be the case that my intuition about the relative probabilities of extant life on Europa/Enceladus vs Mars is correct, but the planetary protection measures appropriate for both destinations are the same.

What I think is more likely though, knowing about other evidence that NASA doesn't consider alien life seriously^[2], and how looking for alien life is associated with low status, is that institutional culture at NASA discourages voicing confusions like mine. If you're behaving as if you expect to find alien life, you're clearly not a serious scientist.

But by default, if you are not expecting to find something, you must expect to not find it. I am thus concerned that NASA, or perhaps the space-exploration-and-scientific-industrial-complex more generally, is and will be resistant to accept evidence of extraterrestrial life. For an organization supposed to be oriented toward discovery, this is not a good bias to have.