Wow, this is so cool.

What are you looking at, Sam?

Take a look!These are pictures from Perseverance, the Mars rover.

This is what the surface of Mars looks like.

I wonder what it would be like to visit and see it myself.

I’d have the coolest spacesuit, and I could see Martian rocks, and eat Martian snacks.

That sounds like a really fun adventure!

You’d need to bring your own snacks though, there’s no food on Mars.

Couldn’t we just grow some food at a Mars farm?

Then we’d have plenty of snacks.

Maybe someday!

Some scientists are already thinking about how we could do just that.

But growing plants for food on Mars has some big challenges that we’ll need to think through.

Let’s think about what plants need to grow.

Can you think of anything, Sam?

Hm, I know that plants need light.

Yes!

From the pictures that Perseverance sent, it looks like there are some sunny days on Mars.

However, the sunlight that reaches Mars is so powerful, it could actually be dangerous to living plants.

Wait, how does that work?

How can sunlight be dangerous to plants if they need light to grow?

Well, it’s like how sunlight is good for people,

but if we are out in the sunlight too long, we can get sunburned.

Plants can also get hurt if they get too much sunlight.

Here on Earth, we have a bit of protection from direct sunlight:

we have a thick atmosphere.

The atmosphere is a thick layer of air that surrounds the planet, kind of like a blanket of air wrapped around the Earth.

Even though air is clear, there are lots of tiny things, like dust and bits of water, floating around in it.

Some of those bits can soak up part of the sunlight before the light reaches us here on Earth.

This protects people and plants from how powerful the sunlight is, even on a bright, sunny day.

But what about on Mars? Doesn’t it have an atmosphere, too?

It does, but the atmosphere around Mars doesn’t have as much air in it.

Mars’s atmosphere is more like a thin sheet of air, instead of our thick blanket of air.

With less air to block the sunlight, the atmosphere can’t protect the surface of the planet from the sun’s full strength.

If we wanted to grow plants there, we would need to build something to shade the plants from the harsh sunlight,

but still give them the light they need to grow.

Like a giant umbrella, or maybe a special greenhouse that would protect the plants.

Good idea!

Now, what other kinds of things do plants need?

I know they definitely need water.

That’s right!

Do you see any place where we could get water on Mars?

Hmm….it looks really dry on Mars.

I don’t see any oceans, or lakes, or rivers.

That’s right.

Here on Earth, we have liquid water all over the surface of the planet.

There is some water on the surface of Mars, but most of it looks pretty different.

Can you see it?

Oh, is that ice?

I know about this one! Ice is the same thing as water.

It’s just water that has gotten so cold, it freezes into a solid, called ice.

Great observation, ice is solid water.

It must be really cold there, if the water is all frozen as ice.

It’s super cold.

On average, the surface of Mars is about negative 60 degrees Celsius, or negative 80 degrees Fahrenheit.

That’s way colder than the inside of a kitchen freezer!

That’s way too cold to grow plants!

Any liquid water we tried to give them would freeze into ice.

Why is it so cold there?

Well, remember how Mars has a different atmosphere than Earth?

The atmosphere on Earth protects us from how strong the sun’s light can be,

but it also helps keep the warmth from what sunlight comes through close to the Earth.

It really is like a thick blanket.

It keeps some of the light out, but it keeps warmth in.

But Mars has a thin atmosphere.

Exactly.

Because Mars’s atmosphere is more like a thin sheet,

light goes through pretty easily, and it doesn’t keep warmth in as well.

So because Mars has a thin atmosphere, it’s really cold there all the time?

Wow!

We’d have to find a way to melt the ice into liquid water for the plants.

If we grow the plants in a greenhouse, we’ll have to heat that greenhouse really well, so the plants and the water don’t freeze.

This sounds like a really tricky challenge.

It is tricky.

The Earth is really special, and we’ve never grown plants on another planet, so we have to think through every step,

and make sure that the plants get the light, water, and other things they need.

But people are really good at solving puzzles and problems, so maybe someday, we’ll be able to grow food right on Mars!

Yeah!

We’ll keep trying new ideas until we find an answer!

And in the meantime, I think it’s time for some Earth snacks.

That sounds like a great idea.

What do you think it would be like to grow food on another planet?

What sort of structure would you build to help protect plants on Mars?

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See ya!