If 100 years of science fiction horror movies have taught us anything,
it’s that we really shouldn’t go around touching alien goo.
However, with NASA’s Perseverance Rover actively searching for Martian Microbes to yeet back home,
just how are we going to protect our planet? Until recently, NASA’s main focus has been on
stopping Earth life from contaminating the planets that we’re trying to study. You can
imagine how the people would react if scientists announced we’d discovered Alien Life on Mars,
only for us to later realise it was actually some Earth bacteria which had hitched a ride on one of
the sensors. Even worse, what if that bacteria were to wipe out the local Martian inhabitants?
Stopping snakes from taking up residence inside our spacecraft’s engine
is relatively easy. Much harder to do is to stop spores and microbes from doing the same thing.
Every cubic metre of air has about 100 thousand different living organisms
and in every cubic metre of soil that number goes up to about ten billion.
Most of these can’t survive outside their natural habitat, and even fewer in the radiation-soaked
vacuum of space. But there are some, such as tardigrades, which most definitely can.
In order to reduce the amount of Earth life that our rover is exposed to,
we construct it inside a positive pressure clean room. This works by pumping in clean filtered
air which then pushes out any contaminants and stops new ones from getting back inside.
Engineers will then bake components of the rover at upto 200 degrees centigrade
and clean others using hydrogen peroxide. While none of these techniques are perfect,
together they make the Perseverance rover one of the cleanest things we’ve ever sent to space.
So, it appears as if Mars is pretty safe, but what about the Earth when we send things back?
This is what’s known as back contamination. I haven’t come to Secret Garden just for the
cool looking backdrop, this once pristine piece of Australian bushland has today been infested
with ipomoea indica which escaped from a local residence’s garden sometime in the 1970s. We don’t
have a great track record for keeping living things out of where we don’t want them to be.
In recent weeks Perth was put under lockdown due a case of coronavirus escaping from strict
hotel quarantine. Invasive species will routinely break through Australia’s strict biosecurity rules
and decimate the local ecosystems. Of all the places we’ve visited in the solar
system, the Jerezo Crater which Perseverance is now calling home, is perhaps the most likely place
to find alien life. Given that we obviously want to take some samples and send them back to Earth,
what steps is NASA taking to ensure that these aliens don’t break out of quarantine?
A spaceship going from Mars to Earth needs to be just as sterile as one going the other way.
We could set up a cleanroom on Mars but this would be very difficult to do
and extremely expensive, so a better option is to split the fleet into two divisions;
one for Mars and the other Earth, with a transfer of cargo occurring somewhere around the Moon.
We need to be sure that the cargo itself isn’t also going to infect the planet. If our samples
are of a geologic nature then great! Blast it with gamma rays to ensure that nothing living still
remains and send it directly to whatever lab you want. If, on the other hand, it is a biologically
interesting sample then sterilising it would go against the whole point of collecting the
sample in the first place, so we need a different option. Here is one suggested by a NASA thinktank.
We start out with what I like to call a Russian Nesting Doll approach. We have our sample and
put it inside a sterilized container. These are what the ones on the Perseverance rover look like.
Next, with this container and a bunch of other containers also containing samples, we put them
inside a larger container and send that one into space. From here we have our transfer of cargo,
putting it inside a large box. This ensures that nothing that’s been in contact with Mars is also
going to get in contact with the Earth. We send this large box down to the surface of our planet
and put it inside an even larger box. We take this box and transport it to a
biosafety level four facility. This would be specially-designed to contain our samples. We
put the samples inside a positive pressure room; stopping any Earth-life from getting in. Next,
around that, we have a negative pressure wall which takes out any contaminants. Finally,
we have where our scientists are operating. It’s another positive pressure room - stopping any
Martians from getting out. We can manipulate our samples by using some specially-designed gloves.
Even with all of this paraphernalia, ultimately something is going to escape.
So what happens next? In “The War of the Worlds”
our Martian invaders are ultimately stopped by the presence of some airborne Earth bacteria
to which they have no resistance. In other stories we have humans being infected by alien lifeforms.
Both of these circumstances are highly unlikely. Infectious diseases are highly specialised for the
specific organism which they tend to infect. While we have cases of diseases jumping from
animal to human, such as with AIDS, bubonic plague, and COVID, these are almost always
from warm blooded mammals to which we are genetically similar. I’m not going to get
dieback from this bush for instance because we are just so genetically different. Now remember,
we did share a common ancestor about 1.6 billion years ago; alien’s wouldn’t have that advantage.
It would be almost impossible for something to jump across that huge gulf in biology.
Ok, so we don’t need to worry about small aliens. What about very large ones with big pointy teeth?
Unfortunately nothing but Sigourney Weaver in a mech suit can stop a very hungry alien from
physically eating you, but on the plus side our Xenomorph is going to starve to death anyway.
It's like how I could eat this handful of sand,
but it's not going to give me any sort of nutritional benefit. Let me explain.
All life on Earth is built with proteins; long complex molecules which provide the structure and
function of the body’s cells, tissues and organs. When you consume something, you can’t just absorb
its proteins, but instead need to break them down into their constituent amino acids. We do this
by using enzymes. Like with a lock and key, each enzyme corresponds to a specific protein. If you
don’t have the right enzyme for the job then that protein is going to go straight through your body.
300 million years ago a plant comes along and invents lignin. This protein is strong, hard,
can be used to transport water, and suddenly we have woody trees growing everywhere. Unfortunately
for the bacteria and fungi of the time, they just didn’t have the right sort of enzymes to
break down these lignin proteins. So, when a tree died it would just stay there; not rotting away or
decaying at all. Over time, these trees piled up and up and up; eventually being crushed down to
form the majority of the world’s coal reserves. While eventually, about 60 million years later,
a bacterium did come along and crack the code for producing just the right sort of enzyme
by that point the damage had been done. Alien lifeforms would be at a similar
disadvantage, maybe even more-so not having had any experience at all to the proteins we have here
on Earth. However, give them a few million years of evolution, or six months in a chemistry lab,
then they may just be able to crack the code. While it's unlikely that alien life could survive
here on Earth, let alone infect or eat us, if we’ve learned anything from exploring our own
planet it’s that life will always surprise you. Probably best to not take any chances.
If an alien lifeform did manage to make its way to the surface then perhaps it could carve out
it’s own ecological niche, outcompeting the local organisms and eventually taking over the planet.
In fact, there is nothing to suggest that this hasn’t happened already and that all life on Earth
is just the descendents that took a ride to Earth on a meteor, crash landing billions of years ago.
When the first humans step foot on Mars perhaps we will really be returning home.
Until then, this has been James Dingley from the Atomic Frontier. Keep Looking Up.