The word "Martian" usually triggers a very specific image. You probably think of a spindly green guy with huge black eyes or maybe those tripod war machines from H.G. Wells. But if you ask a planetary scientist at NASA’s Jet Propulsion Laboratory what a Martian is, they won’t talk about sci-fi. They’ll talk about perchlorate salts, methane spikes, and ancient riverbeds.
Basically, a Martian is any hypothetical inhabitant of the planet Mars. That definition is simple. The reality? It’s complicated. It has evolved from 19th-century "canals" to the grueling search for single-celled organisms buried under a frozen desert. We haven't found one yet. Not a single cell. But the search for what a Martian actually is has become the most expensive and sophisticated scavenger hunt in human history.
The Canal Myth and the Birth of the "Little Green Men"
It started with a mistranslation. In 1877, Italian astronomer Giovanni Schiaparelli observed grooves on the Martian surface. He called them canali. In Italian, that just means channels or grooves. However, the English-speaking world jumped on the word "canals."
Canals imply engineers.
Percival Lowell, a wealthy businessman with a telescope and an obsession, took this and ran with it. He spent years mapping what he thought was a massive irrigation system built by a dying civilization. He published books that convinced the public Mars was inhabited by an advanced race of Martians trying to save their drying planet. It was total fiction, but it set the stage for how we viewed our neighbor for nearly a century.
By the time Orson Welles broadcasted The War of the Worlds on the radio in 1938, the idea of a Martian was synonymous with an invader. People genuinely panicked. They thought the Martians were landing in New Jersey. This era gave us the pop-culture Martian: a being of superior intellect but cold, calculating intent.
What Science Says a Martian Actually Looks Like
Once we actually got close to the Red Planet, the fantasy crumbled. In 1965, Mariner 4 flew by and sent back grainy, black-and-white photos. No canals. No cities. Just craters. It looked like the Moon.
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If Martians exist today, they aren't building cities. Honestly, they’re probably hiding.
Mars is a brutal environment. The atmosphere is 95% carbon dioxide. It’s thin—about 1% of Earth’s pressure. If you stood on the surface without a suit, your blood wouldn't boil, but the oxygen would leave your body so fast you’d black out in seconds. Plus, there’s the radiation. Without a global magnetic field, the surface is constantly blasted by solar flares and cosmic rays.
Extremophiles: The Most Likely Candidates
Scientists now look for "Martians" that resemble Earth’s extremophiles. Think of the microbes living in the subglacial lakes of Antarctica or the hyper-acidic Rio Tinto in Spain.
- Methanogens: These are organisms that produce methane as a metabolic byproduct. Since we've detected seasonal plumes of methane on Mars, some researchers, like those working with the Curiosity rover data, wonder if something biological is "breathing" underground.
- Radiodurans: There’s a bacterium on Earth called Deinococcus radiodurans. It can survive doses of radiation that would liquefy a human. A Martian equivalent might survive just a few meters below the Martian regolith (soil).
The Viking Landers and the Great False Positive
In 1976, we thought we found them. The Viking 1 and 2 missions were specifically designed to find Martians. They carried three biological experiments. One of them, the Labeled Release experiment, actually came back positive.
Gilbert Levin, the principal investigator for that experiment, spent the rest of his life arguing that we had found life on Mars in the 70s. But the other instruments didn't find organic molecules. Most scientists eventually concluded the "life" was just a weird chemical reaction caused by the highly reactive Martian soil.
This taught us a hard lesson: defining a Martian is difficult because the chemistry of another world can "mimic" life.
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The ALH84001 Controversy: Fossils in a Rock?
Sometimes a Martian comes to us. In 1996, a team led by David McKay announced they’d found evidence of ancient Martians inside a meteorite called ALH84001. This rock was blasted off Mars millions of years ago and landed in Antarctica.
Under an electron microscope, they found tiny, chain-like structures that looked like "nanobacteria." President Bill Clinton even gave a televised announcement about it. It was huge.
But science is skeptical. Over the following decade, other researchers showed that those "fossils" could be formed by non-biological volcanic processes. Today, most of the scientific community doesn't believe ALH84001 contains Martians. But the debate pushed us to create the field of astrobiology. It forced us to ask: how do we prove something is alive if it doesn't look like us?
Future Martians: It Might Be Us
There is a third definition of a Martian. It’s the one Elon Musk and NASA’s Artemis program are banking on.
Within our lifetime, a Martian might just be a human born on Mars.
Biological changes would happen fast. In lower gravity (about 38% of Earth's), human bones would thin and muscles would atrophy unless rigorous exercise is maintained. Over generations, "Martians" might grow taller and lankier. Their eyesight might change due to different fluid pressures in the skull.
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We’re moving from wondering "are there Martians?" to "when will we become the Martians?"
Where We Are Searching Right Now
The Perseverance rover is currently in Jezero Crater. Why? Because it’s an ancient river delta. On Earth, where there’s water, there’s life. Perseverance is drilling cores of rock that will be brought back to Earth by the Mars Sample Return (MSR) mission in the 2030s.
We are no longer looking for movement. We are looking for "biosignatures"—chemical fingerprints left behind by ancient Martians who died out billions of years ago when the planet lost its atmosphere and its water.
Key Locations for the Hunt:
- Valles Marineris: A canyon system that makes the Grand Canyon look like a crack in the sidewalk. Seeps of water might exist in the shadows.
- The Polar Ice Caps: Layers of dust and ice that might trap ancient atmospheric samples.
- Subsurface Aquifers: Where liquid water might still exist, protected from radiation by kilometers of rock.
What Happens if We Actually Find One?
Finding a Martian—even a fossilized microbe—would be the "Second Copernican Revolution." It would mean that life is not a fluke. If it happened twice in one solar system, the universe is likely crawling with it.
But there's a dark side called the "Great Filter." If we find dead Martians everywhere, it might suggest that complex life almost always goes extinct before it can leave its home planet. That’s a sobering thought for us.
Actionable Steps for Following the Discovery
The search for Martians is happening in real-time. You don't have to wait for a textbook to be printed.
- Track the Perseverance Rover: NASA’s "Where is Perseverance?" interactive map shows the rover's daily progress and the raw images it sends back. You can see the rocks they think might hold fossils before the scientists even analyze them.
- Monitor the Methane Mystery: Keep an eye on reports from the ESA’s Trace Gas Orbiter. If those methane spikes become consistent, it’s the strongest "smoking gun" for subterranean life.
- Check the "Mars Sample Return" Timeline: This is the big one. Follow the development of the MSR mission. It’s the only way we will get a definitive answer to "What is a Martian?" by putting Martian soil under Earth's most powerful microscopes.
- Volunteer for Citizen Science: Programs like "Planet Four" on Zooniverse often let the public help categorize Martian surface features from satellite imagery. You might literally be the one to spot something weird.
The definition of a Martian has shrunk from a civilization of canal-builders to a microscopic smudge in a rock. But that smudge would change everything. It's not about little green men anymore; it's about whether we are alone in the dark.