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- I'm taking this week off.
Standing in for me is Tom Carroll

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from the incredibly stylish Aspect Science

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who sent one of the best guest video
pitches I've had in a long while.

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And it said, "hi Tom, I've got 12 kilos
of Martian soil simulant

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"and I'm trying to grow a salad."

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- Can we grow crops in Martian soil?

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That's a question I asked
in a recent video of mine,

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and the answer actually
turned out to be: yeah.

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Or at least that it's probably possible
with a bit of tweaking of the soil

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and assuming you figured out

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where to get a good supply
of liquid water from,

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and that you're growing the crops
in a controlled indoor environment.

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What's pretty cool is that Martian soil
has actually been found to contain

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all of the nutrients
needed for a plant to grow.

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But how do we know this?

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I mean, unlike the moon,
no samples of Martian soil,

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which is technically called regolith,
have even been returned to Earth.

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Orbiters, landers, and rovers like those
of the Viking and Pathfinder Missions

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gave us our first understanding of
what Mars's surface was made of,

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and they led to NASA JPL developing

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the JSC Mars-1 Martian
soil simulant in 1998.

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The aim to closely mimic what was found
on the Martian surface.

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Simulants have a range of uses,
like testing out new tools,

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testing out new handling methods,

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and testing out ways to make
use of the material itself.

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But after a while some experiments
with the Martian soil simulants

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showed that they lacked certain
properties of Martian soil,

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which led to the development
of newer simulants.

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And which leads me to these boxes.

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Inside these boxes are 12 kilos

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of Mojave Martian Simulant, or MMS,

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provided by the Martian Garden in Texas.

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So having made a video previously about

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if it's even feasible to use
Martian soil to grow crops,

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the next logical step is to
try to actually grow something.

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So I'm going to try to grow a
Martian salad here on Earth.

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Now whilst I'm getting everything set up

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now would probably be a great time
to ask the question:

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how do they even create this stuff?

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Simulants are basically crushed
blends of Earth materials.

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So the whole process
really revolves around

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finding places on our planet
with a good supply of material

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that has similar
properties to Martian soil.

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The Martian surface is covered in soil
that has a key ingredient of basalt,

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which is a dark, iron-rich volcanic rock.

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The original Martian soil simulant

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used weathered volcanic ash from
an area near Mauna Kea in Hawaii.

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But this stuff, MMS, uses basalt rock

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that's found in an ancient volcano
in the western Mojave Desert,

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which has a very similar mineral makeup
to what's found on Mars.

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They take boulders and
rocks of this basalt,

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which are then crushed into
smaller and smaller particles,

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resulting in a range of sizes
from fine powder to gravel.

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It's then sifted multiple
times to separate it

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into coarse, fine, and
superfine grades of simulant.

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The simulant is missing
an important component

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of Martian soil, though,
toxic perchlorate compounds.

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Now on Mars these could be lethal to crops
and to the humans that eat those crops.

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But luckily for us there are
a range of different methods

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for getting rid of them.

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All right, now I've got
everything set up and ready to go.

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I've got two germination pod trays
split into four columns.

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Column one contains MMS
with a bit of fertiliser.

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Column two contains
MMS with nothing added.

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And for comparison we've got good old
Earth soil in column three.

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And column four contains nothing

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but a water-retaining sheet.

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I'm using four different varieties
of micro green plants,

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which are essentially just plants
that could be harvested really early on.

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I've got pea plants,
sunflowers, cress, and radish.

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And now it's really just a waiting game.

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But let's face it, even
if these things grow,

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they really wouldn't be keeping me full.

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If we're wanting to stay on Mars
for extended periods of time,

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we're going to need to figure out a way
to generate some high-calorie food,

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seeing as it will just be
too heavy to bring with us.

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Some researchers like Dr Weiger Wamelink

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of Wageningen University
have managed to use

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Martian soil simulant and grow
a heap of different vegetables,

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like tomatoes, carrots, and green beans.

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And after having a quick chat with him,
I found out that they've even managed

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to grow some proper potatoes.

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I'm just growing micro greens
because they're quick and they're easy

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so if I screw up it'll be
cheap and easy to try again.

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But hopefully it will be good
and they'll actually grow,

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which it looks like they might.

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It's a few days since
planting the seeds now,

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and look what we've got.

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Everything has started to germinate,

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and I can already taste the
sweet, sweet salad of victory.

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And what led to this stage is
actually pretty fascinating.

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The seeds I planted a few days back

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were lying dormant, where
their growth has stopped

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and metabolism has almost
completely stopped as well.

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Seeds that are dormant stay that way

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until conditions are right for them,

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or they receive a specific
environmental cue.

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For instance, in areas
where wildfires are common,

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seeds can require intense heat or smoke,

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which acts as a sign that
other competing vegetation

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has probably just been cleared by fire.

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When germination begins they
take in a large amount of water

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in a process known as imbibition.

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And the seeds expand and
rupture their outer coats.

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Metabolic changes inside
the seed are triggered

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and enzymes begin digesting food stores,

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leading to the plant
embryo resuming growth.

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The embryonic root makes
an appearance first to access water.

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Then the shoot tip needs to break through
and emerge from the soil.

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Now different plants do this
in different ways,

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but once they do, the first true leaves
can develop and start photosynthesizing,

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allowing the plant to grow more and more.

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And eventually, this will
lead to a full grown plant.

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But I'll be harvesting my micro greens
at a much earlier stage than that.

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At a stage that they're actually
getting pretty close to now.

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It's a few more days later

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and now we've got shoots properly growing

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and can start to see the
differences in everything.

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What's interesting is seeing that
the seeds in the fertilised simulant

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seemed to not be doing well at all.

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Now there are a few reasons
this could be happening,

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but really what this probably
means is that I screwed up

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and used way too much fertiliser.

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But what's really clear is that the plants
in the Martian soil simulant are growing

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a lot slower than the
plants in the Earth soil.

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And this is something I expected

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and something that we would probably
expect from real Martian soil.

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You see, even though Martian soil
has been found

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to contain all the
nutrients needed for a plant to grow,

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some of them are probably
not going to be very abundant,

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or even in accessible forms.

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So it'll have to be tweaked

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by adding in
micro and macroscopic organisms

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and probably using some
forms of fertiliser

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to ensure proper nutrient availability
and nutrient cycles.

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This'll lead to long-term,
sustainable use of soil.

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And will lead to plants
that are nice and healthy

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when you're about to harvest them.

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Which is what I'm about to do
with my micro greens right now.

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It's now 14 days since I planted
all of these micro greens,

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and here they are.

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All right, so it might not
look all that impressive,

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but it's still time for me
to make my Martian salad.

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But wait, I've got to try
and make this look good.

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Okay, so it's not exactly
the biggest feast,

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but I'm actually pretty happy about this.

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I mean, I grew this in
a Martian soil simulant.

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And now I'm about to taste it.

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Hmmm, I mean it's pretty leafy...

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with a little bit of pepper.

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I probably wouldn't recommend it.

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Now clearly this was
not a real experiment,

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and clearly I made some
mistakes in my methods.

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But there are some real
scientists working hard

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trying to make growing
crops on Mars a reality.

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A lot of these experiments are less about

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"can we stick a seed into the Martian soil
and just grow a plant"

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and more about,
"okay, what's our starting point

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"and what do we need to
tweak to make it better?"

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Even though we might still
be at least decades away

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from even landing on Mars,

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let alone settling on it for
long periods of time,

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research done now will make sure that
we're as ready as we can be,

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and it can even lead to better
agricultural practices here on Earth.

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So I'm probably going to try
this whole experiment again,

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but I think I'm going
to try to grow something

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maybe just a little bit bigger this time.

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Tom, thank you so much
for this opportunity.

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I massively appreciate it.

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And thank you for watching.

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Now I'm going to get back
to my absolute feast.

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- Go and subscribe to Aspect Science!
I'd recommend starting with his video

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about what would happen
if a micro meteorite

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hit an Apollo astronaut on the moon.

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I'm back next week and I'll see you then.