Could humans ever call another world home? Take the solar system one place at a time and the honest answer is: Mars, perhaps, with difficulty; a couple of moons, in theory; everywhere else, no, for reasons a child can understand. The idea of humans living on other planets is both fascinating and complex, and the constraints are what make it a good science lesson rather than a daydream.
This is the tour we give when a class has finished arguing about Mars and wants to know what is next. Each stop comes with the one thing that rules it in or out, and there is a build at the end.
What a place needs before people can live there
Four things, and it is worth putting them on the board first. Something to stand on. A temperature a machine can keep you alive in. Shielding from radiation. Water, or the ingredients to make it. Air you can make, gravity you can live with and a way to grow food come next, but a place that fails the first four is out before you start.
Mars: the nearest maybe
Solid ground, a day almost the same length as ours, seasons, frozen water at the poles and underground. Against it: air one per cent as thick as Earth’s and made of carbon dioxide, an average of minus 60 degrees, and no magnetic field to stop the radiation, so the first homes would be buried. It is the only place on this list where the problems are all engineering problems, which is why it gets its own article: can humans live on Mars?
Venus: Earth’s twin, and the worst place in the solar system
Venus is almost exactly Earth’s size, with similar gravity and solid ground. That is where the good news ends. Its thick carbon dioxide atmosphere has trapped so much heat that the surface sits at around 465 degrees, hot enough to melt lead, and the pressure is about ninety times ours, the same as nearly a kilometre under the sea. The clouds are sulphuric acid. The Soviet landers that reached the surface in the 1970s and 80s lasted between twenty minutes and two hours before they cooked.
There is one serious idea: floating cities, fifty kilometres up, where the temperature and pressure are close to Earth’s and a balloon full of our air would float like a cork. Children love this one and it is not a joke; it has been studied properly. Nobody is building it yet.
The giants: nothing to stand on
Jupiter, Saturn, Uranus and Neptune fail the first test. They are gas and fluid all the way down, with no surface, crushing pressure and radiation around Jupiter strong enough to wreck electronics in days. Why you cannot stand on Uranus applies to all four. Cross them off and move to their moons.
The moons: oceans under the ice
This is where the tour gets interesting again. Jupiter’s moon Europa and Saturn’s moon Enceladus almost certainly have oceans of liquid water under thick shells of ice, kept warm by the squeezing of their planet’s gravity. Saturn’s largest moon, Titan, has a thick atmosphere, lakes and rivers of liquid methane, and ground you could stand on, at minus 180 degrees. Jupiter’s Ganymede is bigger than Mercury and has its own magnetic field.
None of them is somewhere to live soon. They are very cold, very far away (years of travel) and, around Jupiter, bathed in radiation. But they are the places where the question “is there life anywhere else?” is being asked most seriously, and a child who knows that Europa has more water than Earth does has learned something most adults do not know.
Beyond the solar system
Astronomers have confirmed more than five thousand planets around other stars, and some sit at the right distance from their star for liquid water. The catch is distance. The nearest star is just over four light years away; with the fastest spacecraft ever built, the journey would take tens of thousands of years. For now, other stars are places to study, not places to go.
The build: pick a world and defend it
Give each group a destination from the list (Mars, a Venus cloud city, Titan, Europa) and a fact card with its numbers: temperature, pressure, gravity, what the air is made of, how far away it is. Forty minutes, a box of recycling, one habitat, then a two-minute pitch to the class on why their world is the best choice and what would kill their crew first. Vote at the end. Mars usually wins. The Venus group usually gives the best pitch.
Why we ask children this
Because it is a real question with no answer at the back of the book, and because every part of it turns into a constraint you can build against. That is the shape of every mission in the Space Club: a hook, just enough science, a build, a test in front of the crew. The tour above is the version we give in our free whole-school assembly, where the hall votes on where they would go. Reception picks the Moon. Year 6 picks Europa, and can tell you why.
Mirko Viviano
Founder of Louno Space Education CIC. Runs space-themed STEAM clubs, workshops and assemblies in primary schools across the UK.
