We've sent five rovers to Mars. Spirit, Opportunity, Curiosity, Perseverance, and Zhurong. We've sent landers, orbiters, and atmospheric probes. We've photographed the surface in enough detail to spot individual boulders. And in all of that, we've been looking for signs of past life. Fossilised microbes. Chemical residues. Geological hints.
Nobody seriously planned for the possibility that something might still be there. Alive. Aware. And very much watching us drop robots on its planet without asking first.
The contamination problem works both ways
NASA has an entire department dedicated to planetary protection. It's called the Office of Planetary Protection, because space agencies are not known for creative naming. Their job is to make sure we don't accidentally send Earth bacteria to Mars and contaminate potential habitats. Every rover is assembled in a cleanroom and subjected to dry heat sterilisation at 112°C.
But if Mars already has inhabitants, the contamination question flips. We've been parking Earth-built hardware on their surface since Viking 1 in 1976. That's fifty years of uninvited deliveries. From their perspective, we've been littering.
And contamination isn't just about bacteria. It's about cultural contamination too. Perseverance carries a plaque, a piece of Martian meteorite that fell to Earth and was sent back, and an experimental helicopter. If you found an alien drone buzzing around your neighbourhood, you'd have questions. Pointed ones.
What kind of life are we talking about?
This matters enormously, because the diplomatic implications of finding bacterial biofilms are quite different from finding something that builds structures.
If Martian life is microbial, the ethical debate is familiar. We've had it about deep-sea vents and Antarctic subglacial lakes. Do we have the right to study ecosystems we might destroy by studying them? Most ethicists say yes, carefully. The microbes don't have opinions on the matter.
But suppose it's more complex. Suppose there's something in the lava tubes beneath Olympus Mons that grows, responds, communicates. Not necessarily intelligent by our standards, but organised. Colonial, maybe. Something like a fungal network or a coral reef, adapted to thin CO₂ atmosphere and brutal UV radiation.
Now you've got a problem. Because we've already landed on Mars multiple times, and nobody checked with the residents.
First contact already happened
This is the bit that unsettles me. If Mars has even basic life, first contact didn't happen in a dramatic radio-signal moment. It happened when Viking 1's landing legs compressed Martian soil on 20 July 1976, and whatever lived in that soil experienced something unprecedented.
We sent a chemistry lab. It scooped up dirt. It heated it. It tested for metabolic gases. The results, incidentally, were ambiguous. The Labeled Release experiment showed a positive result consistent with biological activity. Gilbert Levin, the experiment's principal investigator, spent the rest of his career arguing the data showed evidence of life. NASA disagreed, attributing the results to chemical oxidants in the soil.
Forty-eight years later, the debate isn't fully settled.
If Levin was right, we found life on Mars in 1976, scooped it into a test chamber, heated it, and published a paper about it. That's not first contact. That's an autopsy.
The ownership question
The Outer Space Treaty of 1967, signed by 114 countries, states that no nation can claim sovereignty over a celestial body. Mars belongs to nobody. But the treaty was written assuming nobody already lived there.
If Mars has inhabitants, even microbial ones, the legal framework collapses. The treaty addresses human territorial claims between nations. It says nothing about the rights of indigenous Martian life. There's no clause for "what if someone was already home."
SpaceX plans to send humans to Mars within the next decade. Elon Musk has talked openly about terraforming, about making Mars habitable for humans by thickening its atmosphere and warming the surface. If Mars already supports life adapted to current conditions, terraforming is not colonisation. It's an extinction event with a marketing budget.
Intelligent life changes everything
Suppose, for the full hypothetical, that Mars harbours something genuinely intelligent. Not just alive, but aware. Subsurface, maybe. Using the planet's geothermal energy. Communicating through means we haven't detected because we weren't looking in the right way.
Mars's surface is lethal to complex life as we understand it. Thin atmosphere, no magnetosphere, intense radiation. But underground is different. Mars has lava tubes up to 250 metres wide, easily large enough to shelter an ecosystem. Liquid water may exist in subsurface pockets. The ingredients for complex biology are there, just not on the surface where we've been looking.
If there's an intelligent civilisation underground on Mars, they've watched five of our robots trundle around their roof for two decades. They've seen our helicopters. They've observed our sample collection tubes. And they've made a decision not to make contact.
Which, given how we handle first contact scenarios in our own fiction, might be the smartest thing they've ever done.
What would we actually do?
The honest answer is: argue. For years.
Discovery of microbial life would trigger an immediate scientific mobilisation and a slower political one. There would be calls to halt all Mars missions pending a review of contamination protocols. Those calls would be ignored by at least two space agencies. Papers would be published. Funding would pour in. The microbes would become the most studied organisms in history without ever consenting to the arrangement.
Discovery of intelligent life would trigger something closer to panic. Not Hollywood panic, with cities on fire. Institutional panic. The kind where committees form, press conferences get delayed, and world leaders read briefing documents they don't understand. The UN Committee on the Peaceful Uses of Outer Space would convene. Resolutions would be drafted. Nothing binding would be agreed.
Meanwhile, the Martians would be dealing with their own version of the same problem. They've just confirmed that the clumsy robots falling out of their sky come from a neighbouring planet inhabited by eight billion organisms that can't agree on a thermostat setting, let alone an interplanetary protocol.
I suspect they'd leave the voicemail on read.