The Martian Pet Predicament
What bringing pets to Mars reveals about what we think “healthy” means
3 October 2025
The first time a Martian child asks for a pet, it will not sound like science fiction. It will sound like every child who has ever wanted something unreasonable and deeply necessary.
Please, can I have one?
On Earth, we treat that question as a domestic rite. We negotiate. We make spreadsheets. We promise walks. We explain responsibility with a sternness we do not fully believe in, because we already know the truth. The pet is never only the pet. It is a small, warm experiment in belonging. It is a proof that a home is more than walls and air.
On Mars, the question will arrive heavier. Not because affection weighs more on another planet, but because everything else does. Oxygen. Water. Power. Radiation shielding. Waste management. Feedstock. Launch mass. Every gram will have a story. And when someone asks to bring along a creature that is, in the strictest engineering sense, unnecessary, you will be forced to admit something about the mission that rarely gets printed on the slides.
We are not building a base. We are trying to build a life.
When I spoke with Dr. Jamie Foster, a professor at the University of Florida whose work lives at the boundary where animals and microbes negotiate the terms of health, she approached the question of space pets the way a microbiologist approaches most things: by starting with what you cannot see. “I’ve always been fascinated by how animals and microbes communicate,” she told me, and the sentence landed like a quiet correction. We talk about Mars settlement as if we are transporting humans, tools, and plans. But we are also transporting ecosystems. We carry life whether we admit it or not.
And in Foster’s view, our instinct to keep spacecraft sterile, to treat microbes as the enemy, has been one of the most persistent misunderstandings in modern exploration. “I think we should just give in to this quote unquote contamination,” she said, calmly, the way someone speaks when they have spent years watching the same idea fail under different lighting. It was the kind of statement that makes you blink once and then realize you have been holding a false assumption in your mouth for a long time.
If Mars is the test of our engineering, it is also the test of our definitions. What counts as health. What counts as safety. What counts as home. And whether the creatures we bring with us will be chosen for their utility, their companionship, or for the microbial worlds they quietly tow behind them like invisible luggage.
“It’s not just the companionship. It’s the exchange of microbes.”
The First Spacefarers Weren’t Human
Before we sent people into space, we sent animals, and Foster does not romanticize that history. “Those experiments were rough,” she said. “Sending animals that you knew were on a one-way mission with no real ethical consideration for their health. Those are really tough to ponder about because they were just cruel.”
What changed over the last six decades was not only technology. It was conscience. Or, at least, the pressure of conscience becoming formal. “In the last 60 years, we’ve advanced our compassion for animals and how we ethically treat them in the space environment,” Foster said. She has flown animals herself, and the way she spoke about that experience carried none of the triumphant bravado that sometimes accompanies spaceflight storytelling. There was pride, yes, but also an obvious, practiced humility about what it costs to do these studies well.
Space biology, she explained, gave us the foundation for what animal physiology does under extreme stress. “We’ve learned so much about the immune system and what’s triggering the delays,” she said, and then she pivoted, as she often did, to the subtext that interests her most. The immune system is not only a machine reacting to stress. It is also an ecosystem reacting to the absence of the cues it evolved alongside. “That comes back to our microbial friends,” she said. “Maybe in a sterile spacecraft, they’re not getting the right microbial signals. So that’s causing stress or potential damage to animal tissue.”
The animals taught us about gravity and fluids and orientation. They taught us about stress. They also taught us, indirectly, that we were asking the wrong question when we framed microbes as contamination rather than as infrastructure.
Foster’s answer to the pets-on-Mars question is not a simple yes or no. It is a reframing: if you think the story is about whether a dog can physically survive the journey, you have missed the deeper issue. The deeper issue is whether humans can build a stable living world without the broader living world they evolved inside.
Environmental Probiotics
Before we sent people into space, we sent animals, and Foster does not romanticize that history. “Those experiments were rough,” she said. “Sending animals that you knew were on a one-way mission with no real ethical consideration for their health. Those are really tough to ponder about because they were just cruel.”
What changed over the last six decades was not only technology. It was conscience. Or, at least, the pressure of conscience becoming formal. “In the last 60 years, we’ve advanced our compassion for animals and how we ethically treat them in the space environment,” Foster said. She has flown animals herself, and the way she spoke about that experience carried none of the triumphant bravado that sometimes accompanies spaceflight storytelling. There was pride, yes, but also an obvious, practiced humility about what it costs to do these studies well.
Space biology, she explained, gave us the foundation for what animal physiology does under extreme stress. “We’ve learned so much about the immune system and what’s triggering the delays,” she said, and then she pivoted, as she often did, to the subtext that interests her most. The immune system is not only a machine reacting to stress. It is also an ecosystem reacting to the absence of the cues it evolved alongside. “That comes back to our microbial friends,” she said. “Maybe in a sterile spacecraft, they’re not getting the right microbial signals. So that’s causing stress or potential damage to animal tissue.”
The animals taught us about gravity and fluids and orientation. They taught us about stress. They also taught us, indirectly, that we were asking the wrong question when we framed microbes as contamination rather than as infrastructure.
Foster’s answer to the pets-on-Mars question is not a simple yes or no. It is a reframing: if you think the story is about whether a dog can physically survive the journey, you have missed the deeper issue. The deeper issue is whether humans can build a stable living world without the broader living world they evolved inside.
“I think we should just give in to this ‘contamination.’”
The Pinic Basket Problem
At some point, every romantic Mars conversation runs into the same blunt wall: mass.
“It’s going to be very hard to bring your golden retriever with you to Mars just from a space point of view,” Foster said, and the reason is simple in a way that hurts. Right now, a Mars mission is still defined by what she called a “gigantic picnic basket.” You take everything. You pack every contingency. You accept that there are no Home Depots on the way. And you accept that anything living is not only a passenger, but a supply chain.
“All the dog food and all the cat food,” she said. “You’re almost like glamping at that point, right? You’re bringing the whole house with you to go.”
This is why she believes the first non-human life, beyond our hitchhiking microbes, will be plants. “We are 100% taking plants,” she said. Plants produce oxygen, food, psychological comfort, and a kind of timekeeping. They also create places for microbes to live.
And once you start thinking in ecosystems, the next “animals” that become plausible are rarely the ones we cuddle on Earth. Foster’s mind goes, instead, to creatures that close loops: animals that recycle nutrients, help clean water, support growth systems, and serve as infrastructure in the biological sense.
She offered a list that, on Earth, would sound like a seafood menu. On Mars, it becomes a blueprint. “Oysters or mussels or things like that might make really good,” she said, and then she laughed at herself, because she knew where it landed. “They’re not quite pets.”
But the logic is hard to argue with. Filter feeders as water cleaners. Shells as materials. Nutrient cycling. Food in a pinch. In a place where every system must do double duty, “pet” becomes less a category and more a question of whether the creature earns its keep in the settlement’s metabolism.
This is the part of the Mars future that does not always make it into the glossy art. The first “pets” may be worms. The first companionship may come from gardens. The first animals with names may be creatures nobody on Earth names at all.
And yet Foster did not mock the longing. She treated it like an honest human desire with inconvenient timing. “If you really want a community,” she said, “you have to bring your pets with you.”
“You have to be considerate that they may not want this.”
Squid in the Lunchbox
Foster’s own spaceflight experiment is part adorable, part unsettling, and entirely instructive. In 2021, she sent baby bobtail squid to the International Space Station in a NASA-funded project called UMAMI: Understanding of Microgravity on Animal Microbe Interactions. The design was elegant. Half the squid had their microbial partners. Half did not. Then the question: what happens to stress in microgravity when a developing animal is missing the microbes it evolved to recruit?
The result, as she described it, made the broader point almost too neatly. Animals without their microbes maintained higher stress. Animals with microbes calmed down. “It comes back with the microbes,” she said, “having the right microbes associate with your body can help reduce stress levels.”
The detail that lingers is the age of the animals. “They were the poor little guys. They were 30 minutes old,” she told me. “Welcome to life. You’re going to space in 30 minutes.”
The image is funny until it is not. Thirty minutes old, already launched into a world with no up or down, no familiar environmental signals, and no way to understand why. Foster described the effort it took to make this ethical and scientifically usable. Water, oxygenation, approvals. She described the oversight structure that governs animal welfare in research. “There’s what’s called the IACUC,” she said, explaining the framework. She also noted that NASA required cephalopods, despite being invertebrates, to be treated with standards closer to vertebrate animals. “Cephalopods have shown so much intelligence,” she said.
Space pets always sound like a whimsical question until you trace the question down into its practical layers. What does the animal breathe. What does it eat. What is its waste cycle. How do you keep it from suffering when the humans around it can at least rationalize the misery as “mission.”
In Foster’s experiment, the baby squid had a built-in advantage: an internal yolk sac. They did not need feeding during the brief period. For a cat, or a dog, there is no such convenient biological design. The pet becomes an entire subsystem.
Even when the animal is the size of a fruit fly, the planning takes over your life. Launch scrubs. Backup days. Overproduction to avoid failure. “There’s a lot of gray hair in here because of,” she said, trailing off with the familiar laugh of someone who has lived through schedules controlled by weather, rockets, and the stubbornness of biology.
The question “can we bring pets to Mars” is, in this sense, a proxy for a deeper question. Can we bring a living world to Mars without turning it into cruelty. Can we build habitats that are not just survivable, but ethically defensible.
Gravity Gradients and Radiation Truths
The way Foster speaks about microgravity is less sensational than you might expect. Animals adapt, she said, at least behaviorally. “Even rats on the cage, they learn to hang on to their cage, and then they just kind of go about their business.”
But adaptation is not the same as innocence. Physiology still shifts. Fluids move. Development changes. Orientation systems get confused. The animal might look fine while its body is quietly rewriting its own instruction manual.
Then Foster landed on what she believes is the bigger, more dangerous unknown: radiation. “Radiation is still a huge showstopper,” she said, “more so than microgravity, I would say, in terms of our unknowns.”
This matters for pets because it matters for everyone, and because we have an instinct to imagine the Mars journey as a technical inconvenience rather than a biological exposure. Foster pointed out the difficulty of modeling deep space radiation from Earth, and the fact that low Earth orbit does not provide the same environment because of our magnetosphere.
One of her most intriguing ideas felt, at first, like a piece of set design from a museum exhibit: using water as radiation shielding. “Water is a really good shielding material,” she said. The implication is immediate and strangely beautiful. In a spacecraft or habitat, the line between life support and radiation protection could blur. The same water that keeps you alive could also help keep you safe.
It is not hard to imagine where the mind goes next: aquariums as shielding. Water walls. Habitats with living systems built into their bones.
Foster actually welcomed the image. “I could totally see that you could create a water habitat,” she said, and then she added the ethical snag that arrives with every solution in space. If you position animals behind water shielding, who is closest to the radiation and when. “What’s the ethics of letting them get zapped with radiation before you, the humans do?” she asked.
Even our comforting visions quickly become moral problems when resources are scarce.
Why Fish Make Sense
If there is an animal that slips most easily through the argument about pets on Mars, it is not a dog or a cat. It is a fish.
Fish sit in a strange middle space between companion and infrastructure. They are alive, observable, calming in the way only slow, rhythmic movement can be. But they are also useful in ways that feel almost suspiciously practical for a place where every system must justify its existence.
Dr. Foster kept returning to aquatic life for that reason. Not because fish are emotionally equivalent to dogs, but because they pull double and triple duty in a closed environment. They recycle nutrients. Their waste feeds plants. Their presence stabilizes microbial communities. And, critically, the water they live in is not dead mass. It is doing work.
Water, as Foster pointed out, is one of the best radiation shields we have. In deep space and on Mars, radiation is a more persistent and poorly understood threat than microgravity. A tank of water is not just habitat. It is protection. Wrap a living space in water and you are suddenly solving two problems at once. Life support and shielding. Biology and physics sharing the same volume.
Fish also force a shift in how we define “pet.” They are not there only to be loved. They are there to participate in the metabolism of the settlement. In that sense, they resemble the earliest domesticated animals on Earth more than our modern conception of pets. They earn their place by closing loops.
There is also something quietly comforting about fish in space that is hard to quantify but easy to feel. Astronauts already talk about how watching plants grow helps ground them psychologically. An aquarium adds motion, depth, and a sense of time passing that is not dictated by alarms or schedules. Fish move whether or not you are watching. They remind you that life continues even when you are busy surviving.
From a biological standpoint, fish have already proven themselves adaptable. They have flown. They have reproduced in orbit. Their vestibular systems struggle at first, like nearly every organism removed from gravity, but they adjust. On Mars, with one third of Earth’s gravity, many of the orientation stresses of microgravity may be reduced. Not eliminated, but softened enough to make long-term habitation plausible.
And then there is the uncomfortable practicality that Foster never shied away from. Fish can also be food. Not the primary justification, not the headline, but part of the resilience story. In a fragile settlement, redundancy matters. An ecosystem that can nourish you emotionally and physically is not indulgent. It is strategic.
When people imagine pets on Mars, they often picture animals imported whole from Earth, unchanged, as emotional stowaways. Fish suggest a different future. One where companionship emerges from systems that are already necessary. One where watching life swim through a tank is also watching your habitat work.
If pets arrive on Mars gradually, not by demand but by ecological succession, fish may be among the first creatures we name. Not because they are the most lovable, but because they make sense. And on another planet, making sense might be the first form of care.
And The Winner Is…
If you ask most people to imagine a pet on Mars, they picture a dog with a pressure suit, a cat floating through a habitat like a smug little astronaut, or perhaps a fish tank glowing in a red-lit dome. Foster’s answer is both more practical and, in a strange way, more revealing.
“I think that the first pets will probably be nematodes and worms and other worms and insects and things like that because they’re ecologically so important to the process,” she said.
It is almost funny until you let it land. In a closed-loop habitat, life is not decoration. It is machinery. Worms and nematodes move nutrients. They build soil health. They participate in cycles that keep plants alive. And plants, in Foster’s view, will not only be food. They will be companionship. “Even plants might be the first pets that make it to Mars,” she said.
If you have ever watched an astronaut talk about growing lettuce on the ISS, you understand this immediately. The joy is not proportional to the calories. It is the joy of nurturing something alive in a place designed to be dead. It is the joy of watching time move forward when every day otherwise feels like systems checks and careful conservation.
When Foster described NASA’s interest in multigenerational experiments, she spoke with the careful seriousness of a scientist who knows how much we still do not understand. “No organism has evolved to deal with no microgravity,” she said. The question is whether adaptation could emerge over multiple generations, whether epigenetic changes might accumulate, and what it would mean to ask an animal to become, in real time, something that Earth evolution never prepared it to be.
If you want a pet on Mars, you may be asking for a creature whose descendants will become the first truly off-world domesticated life. Not because we are sentimental, but because we are stubborn. We will build a home wherever we go, and we will keep trying until it looks familiar.
“There’ll be a massive push for that psychological companionship.”
The Temptation To Engineer
The conversation took a turn that felt inevitable: what if we do not bring pets as they are. What if we change them.
Foster did not recoil from the concept. She treated it like a continuation of what humanity has always done. “That corgi didn’t evolve as a corgi, right?” she said. Artificial selection is already a kind of genetic intervention, just slower, framed as tradition.
She tossed out possibilities with a mix of seriousness and humor. Dogs with longer legs to handle lower gravity. Or the reverse, a kind of absurd Martian breeding outcome: “Maybe you can have these big dogs and little legs,” she said. “Space dachshunds.”
The joke hides a real point. Mars will push us into engineering in areas we currently treat as cultural taboos. Food crops resilient to stress. Microbes designed to remediate toxins. “For long-term space flight, we are going to have to engineer food that can survive these very stressful conditions,” Foster said. She also noted the uncomfortable truth that much of what we eat is already genetically shaped by human hands.
The ethical question becomes less about whether we will engineer life, and more about whether we will be honest and careful when we do.
And then, hovering behind the whole discussion, is the psychological truth that is harder to quantify. A human can understand sacrifice. A dog cannot. “We have an enormous mental capacity to adapt to our environments,” Foster said. “Whereas your dogs or your pets might not be able to do that. They don’t know what’s going on.”
This might be the most sobering line of the entire conversation. If we bring pets to Mars, we bring them into a world they did not choose and cannot comprehend. That does not automatically make the act wrong. But it does demand humility. It demands that companionship not become an excuse for cruelty.
If You Have The Money, Anything Is Possible
Foster’s most realistic prediction was not technical. It was economic.
Even if pets are impractical for decades in an academic, scientific model, she believes private spaceflight will distort the timeline. “Unless some very wealthy person just demands to have their pet come with them,” she said, “I really don’t see pets being part of the story for 40 years.”
Then she added the part that makes that timeline fragile. “But that’s not the world we live in.”
A person willing to pay will force the problem early. It will happen in low Earth orbit first. She even imagined it plainly: “I’m sure people will want to bring their pets with them when they take a vacation at the low Earth orbit Hilton or wherever it’s going to be.”
If you want to know what a future culture values, watch what it chooses to spend money on when no one is watching. The first dog in orbit might not be there for science. It might be there because someone could not imagine leaving home behind, even for a few days, without bringing the animal that makes their home feel real.
What follows will not only be cute photos. It will be new questions. What standards apply in commercial destinations. What rules govern animal welfare. Who enforces them. Foster noted how much of this is still being worked out as the ISS approaches the end of its lifespan and commercial stations compete to become the next microgravity research hubs.
Pets will not arrive in the Mars story in a neat, planned way. They will arrive the way many human contradictions arrive: through desire, wealth, and the refusal to treat a living companion as optional.
Please Oh Please Can We Get Him?
Near the end, I asked Foster to imagine the long-term scenario, the one where settlements become towns, towns become cities, and a child on Mars asks for a pet with the same casual entitlement that children everywhere possess.
“If we’ve built cities on Mars,” she said, “then I think that you can bring whatever you want.” Cats, dogs, whatever the infrastructure can support. The only creatures she singled out as still impractical were the ones whose size makes them into moving buildings. “Elephants and giraffes might still be a problem,” she said, and you could hear the grin behind the realism.
Then I asked her a more personal question. If she could go, if she could bring one pet, which would it be.
“If I had to say I could bring animals, I would probably bring mussels with me,” she said, because the scientist in her still thinks in systems. But then she answered the emotional version honestly. “From a pet point of view, I’d probably bring my cat.”
Immediately, she complicated it. Her cat Marley is skittish. “I don’t think she would appreciate that coming to with me,” she said. The question, she reminded me, is not only what we want. It is whether the animal would want it too. “Do you think they would want to go with you?” she asked. “You have to be considerate that they may not want this.”
This is the part of the pets-on-Mars fantasy that tends to get buried under concept art. The animal is not a symbol. It is a creature with a nervous system. It will experience fear. It will experience disorientation. It will not understand why the sky never changes, why the air smells wrong, why the ground feels different, why the sun hits its eyes at a slant that never existed on Earth.
And yet.
We also know what humans do with loneliness. We know what isolation does to cognition and mood. We know that people in extreme environments reach for rituals, textures, and living presence. We know that a pet can be a stabilizing force that no VR simulation, however gorgeous, can fully replace. A living companion reacts to you. It surprises you. It needs you in a way that makes you feel necessary, which is not a small thing when your life is reduced to tasks and survival.
Foster put it in her own grounded way. “I think that the companionship side of thing is so critical,” she said. She simply believes we will try to fill it with plants and artificial environments for a long time before we can justify the costs and ethics of bringing larger animals.
But she also believes the story will eventually catch up to the longing.
Signal Received
Mars will not simply ask whether a dog can survive the trip. Mars will ask what kind of habitat we are building, and whether “healthy” means sterile, controlled, and lonely, or whether it means ecological, messy, and alive.
Dr. Jamie Foster’s answer kept looping back to the same quiet truth: we are not individuals in isolation. We are ecosystems. Microbes are not just threats, but partners and regulators. “We need environmental probiotics,” she said, because when you erase everything in the name of safety, you create the conditions for the worst organisms to thrive. If we want a community on Mars, we will have to learn to cultivate balance, not perfection.
For a long time, the first “pets” may be plants, worms, nematodes, and the unglamorous creatures that make soil and water cycles work. Aquatic animals like mussels and oysters may show up not as cuddly companions but as living infrastructure. Water may become both lifeline and shield. And when someone finally pays enough money to bring a dog or a cat along, it will not just be a headline. It will be an ethical test, a psychological experiment, and a microbial event all at once.
The strangest thing is that this speculative question about space pets ends up sounding like a question about Earth. What do we owe the creatures we love. What do we owe the invisible life we depend on. And how much of “home” is something we can engineer, versus something we have to grow.
If Mars teaches us anything, it may be that you cannot carry a human future across space without also carrying the small, complicated, living world that made humans possible. And someday, in a habitat built not just for survival but for life, a child will ask for a pet and the adults will not laugh.
They will start planning. *
Adapted from Joe Sweeney’s interview with Dr. Jamie Foster for the Aspiring Martians: Everyday Mars episode titled "Pets on Mars" which aired on 30 September 2025.