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The Possibility of Extraterrestrial Life

From Star Wars to Guardians of the Galaxy, it’s clear that alien life fascinates us. Exobiology is the study of all things related to extraterrestrial life. When it comes down to the science of it, there are three questions we should ask ourselves.
  • What are the chances that alien life exists?
  • Would extraterrestrial life look like the life on Earth?
  • Where should we look for extraterrestrial life?
A 3D illustration of little green aliens.

The Drake Equation 


What Is It?

The Drake equation calculates the number of intelligent alien civilizations in the universe. Frank Drake presented the equation in 1961, and it’s been blowing minds ever since.
N = R* ∗ fp∗ ne∗ fl∗ fi∗ fc∗ L
The equation is simple but weird. It’s simple because there are only seven variables. It’s weird because most of the variables are very hard to determine. For example, fl is the fraction of planets that develop life, a number that is way beyond our knowledge. You can see how this equation frustrates exobiologists. 
If you’re interested, you can read more about what the variables mean here.

Can We Use The Equation?

Though we can’t use it yet, the Drake equation is handy in other ways. It brought more attention to the field of exobiology. This increased the number of minds working together to find extraterrestrial life. It also inspired many to find new factors that we should think about in our search.

What Kind of Life Might We Find?

Although it’s possible that there is a planet of aliens made of cheese, it’s unlikely. For this reason, exobiologists turn to Earth to determine what we should be looking for out in space. 
Of all the beings that roam our planet, we have one major thing in common. The molecules that make up our DNA are carbon-based. But, being carbon-based doesn’t mean that we’re going to find aliens that look like life as we know it. 

Simple Extraterrestrial Life

Our first encounter with extraterrestrial life could be through a microscope. Microorganisms are the most prevalent form of life on Earth. For this reason, microorganisms are more prevalent than complex life in our Universe.

An image of protozoa, single-cell organisms.

An illustration of single-celled organisms. They are likely the most common form of life in the Universe.

Complex Extraterrestrial Life

Though they may not be little green people, the life will look alive. I know that sounds silly, but it’s true. The life we find won’t be gas or rocks, they’ll have characteristics of living things. They’ll move, adapt, replenish energy, and reproduce like the life here on Earth. 

Where are People Looking?

Within our Solar System, the places of interest are one of Jupiter’s moons and two of Saturn’s moons. Outside of our Solar System, the top two exoplanets of interest are Kepler 186f and Kepler 442b.

Europa – Jupiter’s Moon

Europa is exciting because it shows signs of heat and liquid water. The surface is water ice and almost completely free of impact craters. This suggests that there are tectonic plates resurfacing the moon. These plates would be a source of energy to heat up the water and sustain life.
An image of Europa.

A photo of Jupiter’s moon Europa taken by the Galileo spacecraft.

Titan – Saturn’s Moon

Titan has a thick atmosphere and lakes and oceans of methane or ethane. The methane lakes could act like water to the life that forms there. Instead of oxygen and carbon dioxide, it would take in hydrogen gas and expel methane gas. Both of those gases are abundant in the atmosphere. Exobiologists believe that life sustains the moon’s atmosphere. 

An image of Titan.

A photo of Saturn’s moon Titan taken by the Cassini spacecraft.

Enceladus – Saturn’s Moon

Though small, Enceladus has a salty ocean under its icy crust. Scientists have seen water vapor containing organic molecules break through the surface. This is evidence for an underground water cycle warmed by the moon’s radioactivity. This cycle could sustain microbial life.
A photo of Saturn's moon Enceladus taken by the Cassini spacecraft.

A photo of Saturn’s moon Enceladus taken by the Cassini spacecraft.

Kepler 186f – Exoplanet

550 lightyears from Earth is a rocky planet of about the same size orbiting in the habitable zone of its star. We don’t know much about the planet, but we do know its temperature is above 32 degrees Fahrenheit. 

Kepler 442b – Exoplanet

1,120 light years from us is another rocky planet larger than Earth. This planet also orbits around its star in the habitable zone. Because its star is weaker than ours, its habitable zone is in a closer orbit. This close orbit means its rotation is much slower than Earths, making the days very long.   

Other Great Resources:

Britannica Kids Article on Alien Life: https://kids.britannica.com/students/article/extraterrestrial-life/274243

Life on Other Planets – Crash Course Kids: Watch Here

Life on Extrasolar Planets – ESA: https://www.esa.int/esaKIDSen/SEMXWOSTGOF_LifeinSpace_0.html

Overview of the Search for Extraterrestrial Life: https://www.factmonster.com/dk/encyclopedia/science/extraterrestrial-life


Written by: Sabryne Fattouh