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- I'm taking this week off. Standing in for me is Tom Carroll
from the incredibly stylish Aspect Science
who sent one of the best guest video pitches I've had in a long while.
And it said, "hi Tom, I've got 12 kilos of Martian soil simulant
"and I'm trying to grow a salad."
- Can we grow crops in Martian soil?
That's a question I asked in a recent video of mine,
and the answer actually turned out to be: yeah.
Or at least that it's probably possible with a bit of tweaking of the soil
and assuming you figured out
where to get a good supply of liquid water from,
and that you're growing the crops in a controlled indoor environment.
What's pretty cool is that Martian soil has actually been found to contain
all of the nutrients needed for a plant to grow.
But how do we know this?
I mean, unlike the moon, no samples of Martian soil,
which is technically called regolith, have even been returned to Earth.
Orbiters, landers, and rovers like those of the Viking and Pathfinder Missions
gave us our first understanding of what Mars's surface was made of,
and they led to NASA JPL developing
the JSC Mars-1 Martian soil simulant in 1998.
The aim to closely mimic what was found on the Martian surface.
Simulants have a range of uses, like testing out new tools,
testing out new handling methods,
and testing out ways to make use of the material itself.
But after a while some experiments with the Martian soil simulants
showed that they lacked certain properties of Martian soil,
which led to the development of newer simulants.
And which leads me to these boxes.
Inside these boxes are 12 kilos
of Mojave Martian Simulant, or MMS,
provided by the Martian Garden in Texas.
So having made a video previously about
if it's even feasible to use Martian soil to grow crops,
the next logical step is to try to actually grow something.
So I'm going to try to grow a Martian salad here on Earth.
Now whilst I'm getting everything set up
now would probably be a great time to ask the question:
how do they even create this stuff?
Simulants are basically crushed blends of Earth materials.
So the whole process really revolves around
finding places on our planet with a good supply of material
that has similar properties to Martian soil.
The Martian surface is covered in soil that has a key ingredient of basalt,
which is a dark, iron-rich volcanic rock.
The original Martian soil simulant
used weathered volcanic ash from an area near Mauna Kea in Hawaii.
But this stuff, MMS, uses basalt rock
that's found in an ancient volcano in the western Mojave Desert,
which has a very similar mineral makeup to what's found on Mars.
They take boulders and rocks of this basalt,
which are then crushed into smaller and smaller particles,
resulting in a range of sizes from fine powder to gravel.
It's then sifted multiple times to separate it
into coarse, fine, and superfine grades of simulant.
The simulant is missing an important component
of Martian soil, though, toxic perchlorate compounds.
Now on Mars these could be lethal to crops and to the humans that eat those crops.
But luckily for us there are a range of different methods
for getting rid of them.
All right, now I've got everything set up and ready to go.
I've got two germination pod trays split into four columns.
Column one contains MMS with a bit of fertiliser.
Column two contains MMS with nothing added.
And for comparison we've got good old Earth soil in column three.
And column four contains nothing
but a water-retaining sheet.
I'm using four different varieties of micro green plants,
which are essentially just plants that could be harvested really early on.
I've got pea plants, sunflowers, cress, and radish.
And now it's really just a waiting game.
But let's face it, even if these things grow,
they really wouldn't be keeping me full.
If we're wanting to stay on Mars for extended periods of time,
we're going to need to figure out a way to generate some high-calorie food,
seeing as it will just be too heavy to bring with us.
Some researchers like Dr Weiger Wamelink
of Wageningen University have managed to use
Martian soil simulant and grow a heap of different vegetables,
like tomatoes, carrots, and green beans.
And after having a quick chat with him, I found out that they've even managed
to grow some proper potatoes.
I'm just growing micro greens because they're quick and they're easy
so if I screw up it'll be cheap and easy to try again.
But hopefully it will be good and they'll actually grow,
which it looks like they might.
It's a few days since planting the seeds now,
and look what we've got.
Everything has started to germinate,
and I can already taste the sweet, sweet salad of victory.
And what led to this stage is actually pretty fascinating.
The seeds I planted a few days back
were lying dormant, where their growth has stopped
and metabolism has almost completely stopped as well.
Seeds that are dormant stay that way
until conditions are right for them,
or they receive a specific environmental cue.
For instance, in areas where wildfires are common,
seeds can require intense heat or smoke,
which acts as a sign that other competing vegetation
has probably just been cleared by fire.
When germination begins they take in a large amount of water
in a process known as imbibition.
And the seeds expand and rupture their outer coats.
Metabolic changes inside the seed are triggered
and enzymes begin digesting food stores,
leading to the plant embryo resuming growth.
The embryonic root makes an appearance first to access water.
Then the shoot tip needs to break through and emerge from the soil.
Now different plants do this in different ways,
but once they do, the first true leaves can develop and start photosynthesizing,
allowing the plant to grow more and more.
And eventually, this will lead to a full grown plant.
But I'll be harvesting my micro greens at a much earlier stage than that.
At a stage that they're actually getting pretty close to now.
It's a few more days later
and now we've got shoots properly growing
and can start to see the differences in everything.
What's interesting is seeing that the seeds in the fertilised simulant
seemed to not be doing well at all.
Now there are a few reasons this could be happening,
but really what this probably means is that I screwed up
and used way too much fertiliser.
But what's really clear is that the plants in the Martian soil simulant are growing
a lot slower than the plants in the Earth soil.
And this is something I expected
and something that we would probably expect from real Martian soil.
You see, even though Martian soil has been found
to contain all the nutrients needed for a plant to grow,
some of them are probably not going to be very abundant,
or even in accessible forms.
So it'll have to be tweaked
by adding in micro and macroscopic organisms
and probably using some forms of fertiliser
to ensure proper nutrient availability and nutrient cycles.
This'll lead to long-term, sustainable use of soil.
And will lead to plants that are nice and healthy
when you're about to harvest them.
Which is what I'm about to do with my micro greens right now.
It's now 14 days since I planted all of these micro greens,
and here they are.
All right, so it might not look all that impressive,
but it's still time for me to make my Martian salad.
But wait, I've got to try and make this look good.
Okay, so it's not exactly the biggest feast,
but I'm actually pretty happy about this.
I mean, I grew this in a Martian soil simulant.
And now I'm about to taste it.
Hmmm, I mean it's pretty leafy...
with a little bit of pepper.
I probably wouldn't recommend it.
Now clearly this was not a real experiment,
and clearly I made some mistakes in my methods.
But there are some real scientists working hard
trying to make growing crops on Mars a reality.
A lot of these experiments are less about
"can we stick a seed into the Martian soil and just grow a plant"
and more about, "okay, what's our starting point
"and what do we need to tweak to make it better?"
Even though we might still be at least decades away
from even landing on Mars,
let alone settling on it for long periods of time,
research done now will make sure that we're as ready as we can be,
and it can even lead to better agricultural practices here on Earth.
So I'm probably going to try this whole experiment again,
but I think I'm going to try to grow something
maybe just a little bit bigger this time.
Tom, thank you so much for this opportunity.
I massively appreciate it.
And thank you for watching.
Now I'm going to get back to my absolute feast.
- Go and subscribe to Aspect Science! I'd recommend starting with his video
about what would happen if a micro meteorite
hit an Apollo astronaut on the moon.
I'm back next week and I'll see you then.


How To Grow A Martian Salad On Earth

林宜悉 2020 年 4 月 1 日 に公開
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