What Will Extraterrestrial Life Look Like?

Illustrator David Aguilar melds art and science to imagine how alien creatures might adapt to their environments

Alien Worlds
It is time that we drop Hollywood’s humanoid view of extraterrestrials. In reality, David Aguilar says, “We are going to find bizarre adaptations.” David Aguilar

Within the next 20 years, human beings could discover life on other planets.

It was this startling prediction—and the subsequent realization that kids sitting in elementary school classrooms today would be the first generation to know where exactly these extraterrestrials live—that stoked David Aguilar’s imagination.

In his latest children’s book, Alien Worlds, Aguilar presents eight worlds, all modeled after Earth-like planets and moons that actually exist in the Milky Way galaxy. Aguilar projects different temperature, gravity, light and water conditions onto these planets—all educated inferences based on the many stages Earth has gone through in its history. In “Ocean World,” for example, the planet’s surface is predominantly water, much like Earth was 450 million years ago, whereas the desert-like “Dying World,” with temperatures ranging from 85 to 140 degrees Fahrenheit, is a glimpse at what Earth could be like about one and a half billion years from now.

Then, Aguilar addresses the bigger question: what will the inhabitants of these worlds look like?

“The popular image is that they look like us. They look like humans: two arms, two legs, a nose, two eyes, two ears and something is just slightly different. They’ve got bumps on their nose or pointy ears or purple colored skin, and so consequently they are alien,” says Aguilar, the director of public affairs and science information at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts. He first got into children’s literature with his 2007 book Planets, Stars and Galaxies. “Sitting on my shelf next to my computer is an array of dog-eared books, that I had as a kid on space, robots and rockets submarines—nostalgic reminders of the exciting ideas that whisked my mind away to other places and other possibilities,” he says. “I want to open young minds out there to the wonders, beauty and sheer awesomeness of their universe.”

But, biologists might say that it is time that we drop Hollywood’s humanoid view of extraterrestrials. In reality, Aguilar says, “We are going to find bizarre adaptations.”

To illustrate Alien Worlds, Aguilar created models of marvelously imaginative aliens out of wood, plastic and clay. He photographed these models, and, then, in Photoshop, added colors, textures and other charismatic features.

Meet his cast of characters:


(David Aguilar)

In Aguilar’s fictional universe, a moon dubbed Chaos orbits Wakanda, a giant ice planet. The gravitational force between the two celestial bodies creates huge ocean tides on the moon. We’re talking mighty waves measuring more than 60 feet tall!

So, how does a marine creature protect itself—especially if, like a turtle, it needs to come ashore to lay its eggs?

“I thought of the airbags in a car,” says Aguilar. His beachrollers—crustacean-like critters—simply inflate an airbag around themselves. “Coming down those big waves, they roll right up to the beach, take care of whatever they are going to do, lay their eggs or reproduce, and then crawl back into the water and swim out.”


(David Aguilar)

Arclandia, a rocky water world where temperatures fluctuate from -25 to 45 degrees Fahrenheit, is much like Earth during its ice ages. On it, Aguilar imagines there being a seal-like creature, with a peculiar way of hunting.

“Instead of jumping down and biting something, it extends its very long tongue with fish hooks on it,” he explains. “It grabs an obaki [the red critter in its mouth, similar to an octopus] and reels it in just like somebody who went fishing for the day out on the ice.”

Two large lung sacs on the seapups’ blue bodies inflate and deflate to help them ascend and descend in the water. And, Aguilar says the “friendly beasts” like to tickle each other.


(David Aguilar)

Just two million miles away from Arclandia is its twin planet, Venera, covered in thick, steamy clouds. “If you can see 20 feet in front of you, it’s a clear day,” says Aguilar.

Given the haze, the illustrator dreams up 10-foot tall coneheads that navigate their world by emitting and receiving odors. “The idea that there could be creatures that communicate using odors instead of words is quite feasible,” says Aguilar. “Ants communicate with odors. When an ant lays odors down in a trail, all of the other ants can follow it.”

Cave Crawlers

cave crawler
(David Aguilar)

“One of the ways creatures will deal with extreme heat is to go underground,” says Aguilar. So, naturally, on Moros, his so-called “Dying World,” where temperatures reach 140 degrees Fahrenheit, cave crawlers burrow into subterranean tunnels. These cantaloupe-sized vermin have multiple eyes and spiky feelers that allow them to flourish in the dark or dimly lit caverns.


(David Aguilar)

“Imagine, if on Earth, one side was always facing the sun, so it was hot and desert-like, like the Middle East, and the opposite side was always facing away from the sun, so it was always in the dark, and it was like Antarctica,” says Aguilar. This is Yelrihs, or the “Infrared World.”

Most of the planet’s life forms inhabit the twilight zone—a temperate band running from the North to South Pole. And yet, strong winds blow in this ring, where warm and cool air from both sides of the planet converge.

Aguilar imagines giant windcatchers, with 30-foot wingspans, that float in the breeze for weeks at a time, descending only to lay their eggs in bodies of water. “It would be like having the most gorgeous kites flying in your sky,” he says.


(David Aguilar)

Scuba diving on Siluriana, Aguilar’s “Ocean World,” would be an incredible, and frightening, experience. The young planet—resembling Earth 450 million years ago—is almost completely covered in water, with just a few volcanoes and continents piercing the surface. And, the sea is full of ghastly predators.

An arrowhead, for example, is a formidable cross between a whale and a shark. Weighing in at 100 tons, the beast is shaped like an arrow, with a triangular head and a strong, slender body measuring about 70 feet. Its sharp teeth are 14 inches long.

Despite the arrowhead’s fangs, it is the mohawk, a spiky turtle-like creature, that will triumph in the clash, pictured here. The mohawk’s spines release a debilitating poison.


(David Aguilar)

A netseref sort of resembles a mushroom, except under its cap is a mass of tentacles.  The animal, about eight feet in height, is known to cling to rocks. It leaves its perch, however, to hunt, whipping its barbed tentacles at prey.

The red dwarf star that orbits Yelrihs beams infrared light onto the planet. Netserefs have eyes uniquely equipped for the conditions. “Everything that they see is in the infrared spectrum,” says Aguilar.  

The artist shows two little critters called preencatchers in this illustration, as the netseref would see them. In infrared, the preencatchers look like colorful heat maps.

“I wanted to introduce to kids that eyes, on different creatures, do not always see the same thing,” explains Aguilar. “We know now that dogs and we think cats see a lot of ultraviolet light.”


(David Aguilar)

Aguilar styled an alien he calls a temmet after an actual fossil of Hallucigenia, a small worm with spikes on its backs and tentacles for legs that lived on Earth during the Cambrian period, about 500 million years ago. “I love that body shape,” he says, “so I put it on a world that had less gravity. It was much larger in size.”

Temmets roam the cloudy planet Venera. The gentle giants have eight legs and long snouts, for sucking water from lakes. In place of eyes, which would be futile in the foggy conditions, temets use sonar for wayfinding. Their spikes emit acoustic signals that bounce off of their surroundings.

“They make great pets,” says Aguilar, playfully. “They will not retrieve a ball. That’s the only problem.”

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