Rishathra, actually.

Fuck reading just the one. Read the whole series. So very much worth it.

NASA is funny. They are always searching for signs of life, past or present, on planets in our system when they can send a lander of some sort. But, if there is a spot where there actually might be a chance of life existing, they avoid it because of the minuscule chance of some bacteria on any rover contaminating the area.

We’ll look for signs of life where it’s hard to find and avoid the areas where there might be a better chance of it.

Sometimes I think about how so many of us look up at the stars and wonder "if there really are aliens out there, why aren't they colonizing the galaxy as fast as possible, as any intelligent species would naturally do?" like it's the thing just anyone looking at the stars might think. we might be the horrifying biomechanical paperclip maximizer that the other aliens in the galaxy have to band together to defeat or face extermination.

Yep i would expect them to send the blankets down from orbit first.

intergalactic tour guide: now if you look to your left, you’ll see the natural habitats of the Xpheno217 species. This is the only location in the whole universe they can live. And to your right, a brand new residential community fit with Walmart and their very own Chick-fil-A.

I'm sorry. I can't let you do that.

This is an interesting idea. If neither biologies used the same fuel molecules then they wouldn't compete for resources, but perhaps they would compete for space? But then if both biologies were that different from each other would they be able to even live in the same environment?

Ah, drat! My one weakness! Claws! Oh, and teeth. So two weaknesses.

Oh, and spikes.

Oh, and fire.

Pointed rocks.

Long falls off of cliffs.

Ok, I have many weaknesses!

I heard on the radio that bacteria is what killed the Martians

I'm a microbiologist. I can speak from experience (my grad research required attempting this a few times) that entirely sterilizing anything of microbes is incredibly difficult regardless of technology level. They are tenacious little fuckers. I'll lay this out for anyone interested.

Gotta Kill 'Em All: Most microbes are fairly easy to kill using simple physical and/or chemical means. Some are more difficult, like spore formers, bacteria that produce little personal suspension pods when conditions are rough.

What matters is you start with huge quantities of microbes, they're everywhere, and you can't see them. All you need is one to survive to potentially reproduce into vast legions of descendants. Even NASA's protocol is about lowering the total number, thereby reducing, not eliminating, the probability of causing an issue. Miss the wrong microbe in the wrong environment and you've inoculated a planet.

Checking Your Work: How do you verify that you successfully sterilized your tool? You might say culturing - swab it and grow that on some type(s) of media. That's NASA's protocol! It's just not very effective.

Not all microbes grow on all media. There are an estimated one trillion microbial species on the planet and we only know how to culture less than about 0.5% of them. The rest are a mystery, largely uncharacterized*. Most sterility testing is for known microbes of consequence, not every microbe in existence.

Microbiology is very often a science of slapping your tool or workspace and exclaiming "good enough!", not absolute precision and 100% efficacy, both of which are practically required if you want to be sure you don't inadvertently pull a "smallpox blankets from space".

*Fun fact: Sometimes people get sick with something atypical, that doesn't get IDed through standard testing. I worked for a time identifying these pathogens via gene sequencing. There was a whole lot of "that's a new one" out there.

FTL travel implies a mastery over spacetime itself. After that, a practical time machine is a matter of engineering details.

We can be sure that we never get there because we are not flooded with tourists from the future. QED.