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So we know what life needs here to work, and we've talked a little about what life COULD look like on other planets. But what about plant life? What could plant life look like on other planets? In this episode of Crash Course Kids, Sabrina chats to us just about that.

///Standards Used in This Video///
5-PS3-1. Use models to describe that energy in animals’ food (used for body repair, growth, motion, and to maintain body warmth) was once energy from the sun.

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Producer & Editor: Nicholas Jenkins
Cinematographer & Director: Michael Aranda
Host: Sabrina Cruz
Script Supervisor: Mickie Halpern
Writer: Allyson Shaw
Executive Producers: John & Hank Green
Consultant: Shelby Alinsky
Script Editor: Blake de Pastino

Thought Cafe Team:
Stephanie Bailis
Cody Brown
Suzanna Brusikiewicz
Jonathan Corbiere
Nick Counter
Kelsey Heinrichs
Jack Kenedy
Corey MacDonald
Tyler Sammy
Nikkie Stinchcombe
James Tuer
Adam Winnik

S: Last time we met, you and I were wondering if there might be creatures on other worlds, parts of other worldly food webs, looking up at the sky and wondering if they were alone in the universe, too.

But, what about plants?

I mean, alien plants aren't out there wondering about anything. Probably. But I wonder if plants here on Earth have plant-like buddies somewhere out there.

Plants on other plants... it's not that big of a stretch. Why?

Food webs, dude. On Earth, plants form the base of the food web. Animals can't exist without them, after all, plants take light energy and turn it into chemical energy. And when animal eat the plants, or eat the animal that ate the plants, they're consuming that energy.

So, plants are vital tot he survival of almost everything on Earth. That means that if you can believe there are creatures on other worlds, you might as well believe there are plants out there, too.

But, how could plants exist on other plants?

(Big question)

Well, think about what plants need on Earth to survive:

First, they need energy from light. Around here they get that from the sun, but on other plants outside our solar system, they could get it from their planets near a star. Alien plants could then use that starlight to power photosynthesis, the system Earth plants use to create sugar from light.

But, they need a few other resources for photosynthesis, too. Like, water and air. Specifically, they need a gas called: carbon dioxide, and a little bit of oxygen to help them use the energy that they make from photosynthesis.

Plus, plants need nutrients to make the chlorophyll they have in their leaves, which they use to carry out photosynthesis. And they usually get these nutrients from the soil.

But if you're a plant you can get by without soil, remember? In an earlier episode we talked about hydroponics, which is a way to grow plants without dirt. Instead, the plants get the resources they need from the water and the air.

So, we know what plants need: Light, water, gases, and nutrients. Now let's check out some potential alien plants!


Let's start with a neighbor. Could plants grow on a planet like Mars?

Mars gets a lot of light from the sun, that's crucial! We've met the plant's first need.

And NASA has recently reported that Mars likely has liquid water flowing on the surface from time to time, too. Great! Another plant need met.there

Martian soil is also good for plants. It contains many nutrients that plants need, like oxygen, hydrogen, carbon, nitrogen, and potassium. Looking good.

What about those gases? Mars has a lot of carbon dioxide, which is great, because that's an essential ingredient that plants need to grow.

But hold up. There are some other major issues on Mars that plants would have to overcome. For one thing, Mars has a very thin atmosphere, about a hundred times less dense than Earth's. And it's very, very cold.

For these and other reason, we haven't found any plants there. But, plants growing in distant galaxies might be perfectly adapted to environments that are totally different from either Earth or Mars.


Well, maybe they have different tricks for capturing light, for example. On Earth, plants appear green because they absorb all the other colors from the light that comes from the sun.

But, what if an alien plant was on a planet orbiting a different star? Not a medium yellow sun, but a small red dwarf? Plants there could look red, blue, yellow, purple, or even greyish-black, in order to best absorb the light from that kind of star.

Now, what if that planet was way too close to the star? Well, maybe it's plants would thrive under rocks or in shadows. To protect themselves from too much light.

What about plants on a planet with low gravity? In that case, maybe plants could float like hot air balloons, far above the surface, high-flying hydroponic plants.

So, conceivably, plants could be adapted to all kinds of alien environments. And like all living things, they would affect the environments they live in.

On Earth, when plants photosynthesize, they produce oxygen. THat's right, plants are not only the base of our food chain, they also provide the life-giving oxygen we need to breathe.

So, plants on other world could create an environment that's able to support alien creatures. Just like how Earth plants support us.


We know what plants on Earth need, so we think that plants could possibly change and adapt to get similar things, depending on the special conditions of other worlds.

And I mean, without plants, how would aliens be able to eat salad? ..... These are the kinds of things I wonder about (and that's why we love you, Sabrina!)