[Music] Last time we met, you and I
were wondering if there might be creatures on other worlds,
parts of otherworldly 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 planets...
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 to the 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? [Music] 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! [Music] 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. 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 reasons,
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. How? 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 its 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 worlds
could create an environment that's able to support alien creatures. Just like how Earth plants support us. [Music] 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. [Music]
