5 Places in the Solar System Where Life Might Be Found

5. Mars

Mars has been home to extraterrestrial life in our imaginations since the earliest days of science fiction. Percival Lowell believed that the canali described by Schiaparelli were canals built by an advanced Martian civilization. H.G. Wells wrote of a Martian invasion of Victorian England.

Although the Viking landers showed us an apparently lifeless Martian surface, it is possible that Mars once supported life, and may yet do so. After all, it possesses a (thin) atmosphere, essential nutrients, and fairly abundant solar energy. There is evidence that water ice is abundant, and that liquid water once flowed across the surface. Might there be Martian microorganisms hiding beneath the surface, protected from the harsh chemicals and UV radiation?

4. Titan


After Mars, Saturn’s moon Titan may be one of the most popular places in the solar system for speculation about alien life over the past several decades. Observed by Pioneer 11 and Voyager 1 only as a hazy world surrounded by an opaque atmosphere, the Cassini probe and Huygens lander provided much more information about Titan.

Though too cold for liquid water, Titan’s surface is covered by lakes of hydrocarbons. Its atmosphere is mostly nitrogen, along with methane and other hydrocarbons. This has led astrobiologists to speculate about life forms not based on water, but instead using methane or ethane as a solvent.

3. Europa


This moon of Jupiter possesses a subsurface ocean, kept liquid by the heat from tidal forces exerted by Jupiter. This same tidal flexing could create undersea hydrothermal vents, and there is evidence to suggest that the ocean is in contact with a rocky surface. The presence of a liquid ocean, coupled with an energy source in the form of undersea vents, and a rocky undersea surface as a source of minerals, suggests that Europa is a place that could support life.

Proposals have been made for exploration of the Europan ocean, but the high-radiation environment around Jupiter, difficulties involved in boring down to the ocean, and concerns about contaminating the moon with Earth life have prevented such a mission so far.

2. Pluto


Yes, the poor non-planet at the edge of our solar system could potentially support life.

Pluto possesses a very thin atmosphere of nitrogen, methane, and carbon monoxide, and though it was once thought that the atmosphere would freeze when Pluto was farthest from the sun, scientists now believe that it remains gaseous throughout Pluto’s orbit.

Additionally, the New Horizons probe revealed the existence of tholins, a type of organic compound, on the surface of Pluto. If the extreme conditions of the surface make it uninhabitable, life might still exist deep beneath the surface, in a possible sub-surface ocean.

It should not be surprising, then, that science fiction writers have from time to time picked Pluto as a potentially life-supporting world.

Honorable Mentions

  1. Venus – Once imagined as a lush jungle world, we know now that our sister planet suffers from a stifling atmosphere with clouds of sulfuric acid and surface temperatures that can melt lead. Still, extremophiles do exist on Earth, and some speculate that life might survive high in the atmosphere of Venus.
  2. Ganymede – Another of Jupiter’s moons, Ganymede is suspected to harbor a subsurface ocean with more water than all of Earth’s oceans combined. Might something be swimming beneath the surface of this largest Galilean satellite?
  3. Jupiter – Hard as it might be to imagine life on a planet with no solid surface, Carl Sagan speculated that balloon-like organisms might float on the Jovian breezes, consuming microorganisms likewise swept around by the gale-force winds. Concept art was even created for his legendary Cosmos series.
  4. Earth. Ok, this one is a cheat. Not only does the third rock from the Sun support life, we’re also fairly certain that there’s intelligent life to be found here. Somewhere. If you’re searching for life in the solar system, Earth is your safest bet.

1. Enceladus


En-what? Enceladus, one of the larger moons of Saturn, is yet another world possessing a subsurface ocean. Observations by the Cassini spacecraft suggest a geologically active world, with geysers containing hydrocarbon compounds and indicating the presence of a high-pH ocean.

Though highly alkaline and buried deep within the moon, scientists speculate that this ocean may provide the energy sources and support the complex chemical reactions needed for life to form. Life on Enceladus may be powered by chemosynthesis, with hydrothermal vents being a source of chemical energy for the Enceladan microbes.

Incidentally, if you are ever uncertain about pronunciation, Space.com has a handy guide for pronouncing the names of all the planets and moons in our solar system. Yes, even the eighth planet…

Cosmic Trailblazers

Wrote this a while back based on a writing prompt from /r/writingprompts:

“Alexander Pope wrote, ‘Nature and nature’s laws lay hid in night. / God said, Let Newton be!'” As soon as I flicked the lighter, the spherical flame danced near my thumb. I touched it to the end of the rolled paper, then brought the other end to my lips and inhaled. “And all was light.”

Forty-eight hours until my next duty shift. With only one week until the SpaceX ship “Ghost of Christmas Future” made its historic landing, I was beginning my final scheduled weekend break. Two days with no landing simulations, no laboratory activities, no maintenance duty. Just me, myself, and I.

And my roommate. In the hammock nearby, he chuckled and stretched out. Most of his free time was spent staring out the porthole, watching Mars grow ever larger. “Care for a hit, Carl?” I offered, but he held up his palm and shook his head. “You know I can’t,” he said sadly.

I shrugged and took another puff. “You know we’re naming our colony after you?”

“Sagan City,” he nodded, still staring out the porthole. “It must’ve bruised your CEO’s ego considerably not to name it Muskopolis.”

“Elon Musk himself allowed us to vote. The scientists were adamant.” Smoke poured from my lips as I spoke, curling in unusual ways as my breath yielded to the air currents from the ventilation system. I closed my eyes for a moment. There was something about microgravity that made mary jane extraordinary. “You’re not pleased? It’s quite an honor.”

“Newton would be pleased,” Carl answered. “I might’ve preferred something more whimsical, like ‘Helium’.”

I imagined stepping out of the “Ghost of Christmas Future” airlock, my boots printing the Adidas logo into the Martian regolith, and there in the distance, Dejah Thoris, princess of Mars, beckoning me forth. “You’d have my vote, but you’d be the minority. I think ‘Bradbury’ was the runner-up.”

“Yes, he told me so.” Carl also closed his eyes. His spectral chest rose and fell in imitation of breathing. His face grew melancholy, as though recalling the experiences of his youth.

“I don’t get it, Carl. You’ve been dead all these years. A ghost. You can’t eat or drink. I’ve never seen you sleep. You obviously can’t blaze, and I’m guessing you can’t get laid, either…”

He nodded wearily.

“So why do you stick around? Why do any of you ghosts stay?”

You could say that “Ghost of Christmas Future” was haunted by its past. Percival Lowell. Angeline Stickney Hall. Robert Goddard. Neil Armstrong. To most of the crew, this would be a metaphor for “standing on the shoulders of giants,” as Isaac Newton likes to say. But luck made me one of the point-zero-zero-one percent of humans who is psi-sensitive, and to me, ghosts were as real as farts in an elevator on Taco Tuesday, and often equally unpleasant.

Not the scientist ghosts, mind you. Notwithstanding the unpleasant supernatural chills, pre-mouthwash-era halitosis, and constantly having to lie to the ship psychiatrist, it was amazing to work shoulder-to-spectral-shoulder with the greatest intellects in human history. To be tutored in physics by Albert Einstein. To hear Isaac Asimov opine about our onboard computer AI. Enrico Fermi himself saved my bacon during an incident with a portable nuclear reactor.

But by my estimates, the ghostly population outnumbered the living, breathing crew by more than 50:1. And most weren’t cool like Carl Sagan. There were mindless thrill-seekers hoping to find a bigger rush in death than they did in life. Trekkies from the Original Series days, sixty years ago, who died with their Spock ears on. And at least one prattling geologist from Saint Thomas Francis University who probably bored himself to death. Looky-loos of all sorts.

“No one was as surprised as I to learn that ghosts exist,” Carl explained. “In the thirty-two years I’ve been dead, most of the ghosts I’ve met eventually grow bored, and decide to move beyond.”

“And you?”

“Just because ghosts exist, we cannot presume that there is a ‘beyond’. It’s possible that all these ghosts are simply giving up their existence. Not moving into a heaven or a hell… Just oblivion.”

“And that doesn’t appeal to you?”

Carl thought for a moment. Stars twinkled in his eyes. “When there’s still so much out there to see and discover?” He shook his head and gestured out the porthole. “Someday, perhaps. But not in my lifetime. Not in a hundred lifetimes. Perhaps… not even in billions and billions of lifetimes.”

“Ha, you finally said it!” I threw my spent butt at him in my excitement. It passed through him and bounced off the wall. Ashes scattered in all directions. I drifted over to corral the debris into the ventilation filter. Nothing in the room was flammable, but I wanted no evidence of contraband floating around.

After a while, I positioned myself near the porthole, a few feet from Carl. My velcro shoes gripped the floor, and I swayed in the draft from the air duct. We stared at the red orb, the harbinger of war, our future home. “Carl, dude…” I said, enthralled by the view. “Mars is so big!”


Resonant Cavity Thrusters

EmDrive. Q drive. Cannae drive. All of these are a class of devices known as resonant cavity thrusters, and for the past few years they’ve been popping up in the media from time to time.

What’s the big idea?

Take an ordinary household magnetron (you’ll find one in every microwave oven). Use it to pump microwave radiation into a resonant chamber of a certain shape (a metal box that’s wide at one end and narrow at the other.)

Turn it on and voilà: even though nothing is emitted from the system, you’ll detect a very small anomalous force pushing the chamber.

Continue reading “Resonant Cavity Thrusters”


It was too late to turn back — for all of them. Three weary explorers stared out the porthole as the spacecraft A Shot in the Dark hurtled toward Comet 266P/Christensen.

“Collision course set,” announced Michelson as the main rocket engine died. “That’s the last of our fuel.”

Dr. Grigori stared out at the stars.

“What should we tell Earth?” Dr. Markova asked.

Michelson shrugged. A world now plagued by climate shifts, mass extinction, and natural disasters too numerous to list needed hope, not more bad news.

It had started decades prior. A mysterious radio signal from the stars. “Wow!” writ large in the margin by a grad student. Astronomers worldwide tuned to 1420 MHz, but heard only silence. For decades they wondered: was the Signal merely radio noise, or the first evidence humankind is not alone?

The mystery deepened: the Signal returned, and Comet 266P/Christensen was pinpointed as its source, but against expectations, the Signal showed hints of advanced intelligence. So billions of dollars in venture capital funded A Shot in the Dark — a one-way mission of discovery. Investors dreamed of alien technologies to save the world and pad their bank accounts. If successful, the crew would be hailed (whenever future investments could fund a rescue mission) as heroes by a world desperate for hope.

But just before arrival, Dr. Grigori made a horrifying discovery. “The Signal is not from the Comet; the comet’s halo merely reflects and amplifies it.”

“From where?” Michelson asked.

“Are you familiar with the Gaia Hypothesis?” asked Markova. “That Earth is essentially a single, unified organism?”

“Decades of pollution,” muttered Grigori. “Neglect. Abuse.”

Markova looked grim as the Signal played over the speakers. “This Signal,” she explained, “is the death rattle of Planet Earth.”

Written for Cracked Flash Fiction, Year 1 Week 38, where the prompt was the first sentence of the story. This story references the famous Wow! Signal, along with recent (at the time) articles suggesting that the signal may have originated from two comets.

X One

Nearing the end of the A-to-Z challenge! X is for xenon, a noble gas and element 54 on the periodic table. Among its many uses, Xenon is sometimes used as the propellant for ion drives. Ion drives are low-thrust, but have high specific impulse, and are thus useful in deep space probes, where total delta-v is more important than quick acceleration.

Target acquired. It’s an Earth-built vessel known as an XF-314, manned, hiding in the shadow of a nearby asteroid. To my optical sensors it’s invisible, but nothing could conceal the heat signature from its engines. Another human pilot is about to make a run at the quarantine zone.

I ramp up the charge on my ion drive, aiming the stream of xenon ions to accelerate me into an intercept course. In space, slow and steady wins the race.

As soon as he sees me — I’ve decided this human pilot is a he — he begins his evasive manuevers. Jinking left and right, he dives the XF-314 toward the asteroid, then climbs out again in a waste of precious delta-v. Despite his overdramatic piloting, his accelerations are unimpressive. I could outmaneuver him easily, reaching accelerations that would crush his fragile body. Never send meat to do a drone’s job.

Rather than attempt to match his frantic evasions, though, I simply keep matching his average velocity. He fires a burst from his turret cannon, but within nanoseconds I realize that his desperate shots will miss me by several hundred kilometers. Human brains are notoriously bad at numerical calculations, and shockingly poor at strategizing in three dimensions. It’s a consequence of having evolved on a two-dimensional surface, with sky above and soil below.

If I could feel human emotions, I would feel sorry for the humans. Squishy, short-lived meat-beings, forced into quarantine in the inner solar system. But history has shown that humans cannot peacefully coexist with us drones, thus necessitating their forced isolation from drone civilization.

Soon I can predict his maneuvers with 95% confidence, so I lob some shot — just a cluster of iron slag pellets — into his path. Less than a thousand seconds later, his XF-314 collides with the cloud of projectiles at a relative velocity of a thousand meters per second, shredding the cockpit. His pseudorandom jinking maneuvers cease: the XF-314 assumes an even more predictable Newtonian trajectory around the asteroid. Target neutralized.

Split Decision

Day nineteen of the A-to-Z challenge. S is for spacesuit, a special suit designed to keep astronauts alive in space. This story is a continuation of Countdown to the Comet and Killing Blow, regarding an antimatter comet threatening to destroy Earth, and a secret conspiracy to stop it.

Against the backdrop of stars, Comet Spencer Jones glowed like the surface of the Sun. Giordano knew this was an illusion: her spacesuit HUD interfaced with the shipboard computer to project a false-color image. Though the comet shone brightly in gamma frequencies, it was dark as the black sands of Maui in visible light. She tried to focus on calibrating the railgun, rather than the eerie glow that constantly hovered in her peripheral vision.

“Your heart rate is increasing once more,” her mission commander’s dull voice came through the headset. “One-hundred-and-sixty-five bee-pee-em. Elapsed time is now seventy-five minutes.”

“Roger that, Commander,” responded Giordano, trying to hide her exasperation. “Everything under control.” After passing six months in the claustrophobic (but efficient) Japanese-built habitation module with her two shipmates, Giordano needed some space. Now during this spacewalk, she found that even infinite space was not big enough for her to escape Commander Shergill.
Continue reading “Split Decision”


Day 17 of the A-to-Z Challenge. Q is for Quaoar, an object in the outer solar system. Discovered in 2002 and named after a deity from Tongva mythology, Quaoar arrived on the astronomical scene during a period of turmoil. You see, it was not alone…


In 1992 (right around the time I was in grade school, possibly learning the mnemonic “My Very Educated Mother Just Showed Us Nine Planets”), astronomers discovered an object that received the provisional name 1992 QB1. This object turned out to be the first Trans-Neptunian object discovered since Pluto (and its moon Charon).

This prompted a renewed effort to locate similar objects, which came to be known as cubewanos (QB1-ohs). It turns out, there are a lot of similar objects in the outer solar system. In 2000, astronomers discovered the object that was eventually named Varuna. Less than two years later, Quaoar was discovered, and it was pretty big. Bigger than QB1.

Many other Trans-Neptunian Objects were found during the first few years of the 21st century. Some of them rival Pluto in size — and the discoverers naturally wanted their discoveries classified as planets. “I discovered a planet” is an impressive quote: it fits on a business card or a t-shirt, and it’s a real hit as a pick-up line.

Were Quaoar, Ixion, Sedna, Haumea, Makemake, and the other objects on the growing list of Trans-Neptunian Objects really planets? No one could say, because the International Astronomical Union had never officially defined the word planet.

Then in 2005, the same group that discovered Quaoar discovered another object — and it was as big as Pluto, or bigger. Obviously, if Pluto is a planet, then the new object must also be a planet, right? (This object received the rather fitting name of Eris — the goddess of discord, who causes arguments.)

A similar crisis had arisen two centuries earlier: astronomers discovered Ceres, and decided it was a planet… then discovered Pallas, Juno, Vesta, etc. The solution then was to create a new classification: these objects would be known as minor planets, though most people just call them asteroids.

In 2006, the IAU decided to resolve the issue with a similar cop-out solution, creating a definition for planet that deliberately excluded these new objects — along with Pluto — but then creating a new classification of dwarf planet. Pluto and Eris (along with Ceres) were specifically called out as dwarf planets.

(As a consolation to Pluto, the IAU also created the classification of plutoid, which at the time they vaguely defined as anything kinda like Pluto.)

After the IAU vote, our solar system was one planet lighter, and astronomers were free to continue discovering inconveniently large objects without fretting over whether they were planets.

But really, Quaoar doesn’t care about the arguments, the disputes over definitions, or the glory of planethood. Quaoar doesn’t care whether we call it a planet, dwarf planet, Trans-Neptunian Object, cubewano, or late for dinner. Quaoar just is.

And 1992 QB1? It’s still just called QB1.

O’Neill Cylinder

For day fifteen of the A-to-Z challenge, I thought I would take a brief break from fiction and take a look at a type of space station. O is for O’Neill Cylinder, which some may know it as “Island Three,” where Island One and Island Two are the comparatively much smaller Stanford Torus and Bernal Sphere.

Interior of an O’Neill Cylinder. Public domain photo from Wikimedia.

Proposed by physicist Gerard O’Neill, the design was for two side-by-side counter-rotating cylinders, each five miles in diameter and twenty miles in length, connected by a support structure.

Each cylinder would consist of six alternating strips of “sky” (transparent windows and mirrors to allow sunlight into the cylinder) and “land,” providing a habitable surface area of over 100,000 acres. Maneuvering would be handled without thrusters, by taking advantage of the angular momentum of the cylinders.

Variants of the O’Neill Cylinder have been seen fairly often in science fiction.

Babylon 5
“Humans and aliens wrapped in two million, five hundred thousand tons of spinning metal… all alone in the night.” – From the Babylon 5 season 1 opening monologue

“The mass of Rama was at least ten trillion tons; to any spaceman, that was not only awe-inspiring but also a terrifying thought.” – Rendezvous with Rama, Arthur C. Clarke

Brian Versteed provides the Kalpana One space settlement concept. While it’s closer in size and design to a Stanford Torus, there’s some rather nice artwork of the concept.

Orion’s Arm has a page with concept art for a McKendree Cylinder. An enormously scaled-up version of an O’Neill Cylinder, a McKendree Cylinder can have as much land area as a small continent.

Making Out in the Main Belt

Halfway through the A-to-Z challenge! M is for mothership, a large ship that carries smaller ships. Flying saucers and bug-eyed monsters are not necessarily involved, though they certainly make things more fun.

Through the porthole, the stars spun in slow, lazy circles. Jako tried to ignore them, and the queasy sensation of microgravity. Instead he focused his attention on his wristpad display, frantically manipulating figures in a spreadsheet.

“How can you do homework at a time like this?” This tied the record for longest sentence Liarna had spoken to him in their high school career. Jako chuckled; all it took for a girl to talk to him was to be trapped in a cramped sardine can in the middle of the Main Belt. He wondered what it would take for him to get a date for senior prom.

“It’s not funny, Jako! Someone’s going to come looking for us, right?” Their escape capsule was speeding away from the mothership, in orbit of minor planet 535 Montague, at a velocity of thousands of meters per second. It would take days for a search and rescue team to find them.

“Someone will come looking for us. It’ll just take longer for them to find us than to catch your delinquent boyfriend.”

“What’s so bad about Dynnon?”

Jako stopped swiping at his wrist display and looked her squarely in her gray eyes. “He and his jock friends stuffed me into an escape capsule and launched it?”

“I’m sorry,” she said. “I tried to stop them.”

“I know. Thanks.” Jako returned to his calculations.

“It’s so hot in here. Worst field trip ever.” She unbuttoned her top button, then noticed his focus on his wristpad. “Seriously?! How can you be doing homework?”

“Titan was the worst field trip ever.” Which teacher had thought that taking a class of giggling high school freshmen to a moon with a methane atmosphere was a good idea? “And this is not homework,” Jako explained. “I’m calculating how long the air will last us in here.”

Liarna’s face paled. “Are we going to die?”

“Someday. But life expectancy for a girl your age is a hundred and forty-eight. Life support in this escape pod should easily last two weeks. We’ll be picked up long before then.”

Liarna tugged at her collar. “Then why is it so hot?”

With his fist, Jako bumped a large green pushbutton on a nearby control panel. The iris-style hatch above them opened, and air rushed outward. Liarna gasped, but quickly regained her composure and peered up through the hatch.

“Inflatable habitat,” explained Jako. “It provides a little more breathing room.”

Liarna tentatively stood up, gripping the handholds to position herself in zero-g. With a gentle push, she floated through the hatch, into the inflated space. The walls were transparent plastic, but only the two dozen brightest stars were easily visible through its slightly reflective surface. “Wow,” she said. “Great view. You should come up here.”

With a shrug, Jako turned off his wrist display and floated off to join her. She pointed out a bright blue star. “Isn’t that Earth?”

Jako blinked. “Yes. How’d you know?”

“I do have interests other than my delinquent boyfriend,” she said, rolling her eyes at him. “You’re too quick to stereotype people. I’m not a ditzy blonde, and Dynnon isn’t a meathead jock. Did you know he’s into romance poetry?” She tapped her own wristpad, then showed Jako a file from her private folder.

Jako stared at the display in disbelief. “Until this moment, I never would’ve believed Dynnon could write a sonnet.”

“Would you believe he’s not even my boyfriend? He’s dating his teammate Mato.” She paused uncomfortably, as though she had spilled a secret. “Don’t tell anyone. His parents are really old-fashioned. They would never understand him dating an android.”

He nodded, holding a finger to his lips. “Your secret is safe with me.”

The two of them floated in the center of the ellipsoidal inflated habitat, adrift in a sea of stars. “We’re pretty far from Montague by now. It might be days before they find us.”

“Two or three days, maybe,” Jako shrugged. “The mothership can detect us easily; it just takes a long time to catch us at this velocity.”

Liarna rested her head on his shoulder. Jako’s heart skipped a beat as she leaned into his ear and whispered, “Would you like to help me with my physics homework?”