Humans have already left Earth, but only briefly and never farther than the Moon. The real question most people are asking is whether we’ll ever live somewhere else, and the honest answer is: the groundwork is being laid right now, but the biological, psychological, and engineering challenges are enormous. Here’s where things actually stand.
What’s Happening Right Now
NASA’s Artemis program is the closest thing to a concrete timeline for getting humans beyond low Earth orbit again. Artemis II, scheduled for early 2026, will send four astronauts around the Moon on a 10-day flight, the first crewed deep space mission since Apollo 17 in 1972. It won’t land, but it will test the spacecraft and rocket systems needed for everything that follows. Artemis III will attempt the first crewed lunar landing in over 50 years, though NASA hasn’t locked in a firm date.
Behind the scenes, a small space station called the Lunar Gateway is taking shape. Its first modules are set to launch toward the Moon in 2027. Gateway will orbit the Moon and serve as a staging point for surface missions and, eventually, deeper trips into the solar system. Fifty-five countries have now signed the Artemis Accords, a set of international agreements governing peaceful cooperation in space, which signals broad political will to keep this moving.
SpaceX’s Starship system represents the private-sector side of the equation. Elon Musk has estimated launch costs as low as $10 per kilogram to orbit, a figure that hasn’t been proven yet but that would be transformative if even roughly accurate. For context, current launch costs typically run in the thousands of dollars per kilogram. Cheap, frequent launches would change the math on everything from building orbital habitats to sending cargo to Mars.
The Moon First, Then Mars
The current strategy treats the Moon as a proving ground. Living and working on the lunar surface lets engineers test habitats, power systems, and resource extraction in a hostile environment that’s only three days from home if something goes wrong. Mars is a six-to-nine-month journey each way, with no option to abort.
One critical technology has already been tested on Mars itself. In 2021, an instrument aboard NASA’s Perseverance rover pulled oxygen directly from the Martian atmosphere, which is 96% carbon dioxide. After a two-hour warmup, it produced oxygen at a rate of 6 grams per hour, with a design capacity of up to 10 grams per hour. That’s a tiny amount, roughly enough for one person to breathe for about 10 minutes per hour of operation. But it proved the concept works. A future version, scaled up dramatically, could produce both breathing air and rocket propellant from local resources, eliminating the need to haul everything from Earth.
Water recycling has also hit a milestone. The International Space Station’s life support systems now recover 98% of all water on board, including moisture from the air and even from crew urine. Before recent upgrades, recovery hovered around 93 to 94%. Getting close to 98% is considered the threshold needed for long-duration missions where resupply isn’t possible.
What Space Does to the Human Body
The engineering problems are solvable with enough time and money. The biological problems are harder. In weightlessness, astronauts lose 1 to 2% of their bone mass per month, a rate first documented in the 1970s during Skylab missions and confirmed repeatedly since. On a three-year Mars round trip, that adds up to potentially catastrophic skeletal weakening, comparable to severe osteoporosis. Exercise protocols on the ISS slow the loss but don’t eliminate it. Artificial gravity, generated by spinning a spacecraft, is a theoretical solution that has never been built at scale.
Radiation is the other major threat. Earth’s magnetic field and atmosphere shield us from cosmic rays and solar particle events. In deep space, that protection disappears. A round trip to Mars would expose astronauts to roughly 300 to 600 millisieverts of radiation over about three years. For comparison, the normal background dose on Earth is about 2.4 millisieverts per year. That elevated exposure increases lifetime cancer risk and may cause neurological damage, though the exact long-term effects of chronic deep-space radiation on humans remain uncertain because no one has experienced it yet.
Reproduction adds another layer of concern. Research from spaceflight experiments and ground-based simulations shows that weightlessness disrupts nearly every stage of mammalian reproduction: sperm and egg development, fertilization, and early embryo growth. The mechanisms include oxidative stress, DNA damage, and changes to how cells communicate during critical developmental windows. If humans can’t reliably reproduce off Earth, permanent settlement isn’t possible, only rotation-based outposts.
The Psychological Wall
Years of isolation research, including NASA-funded missions where small crews lived in sealed habitats simulating Mars conditions for 8 to 12 months, have revealed a consistent pattern. Stress runs high and fluctuates unpredictably. Crew members can’t escape each other, which creates intense social friction. Conflict management becomes trial and error, cycling through criticism, defensiveness, avoidance, and stonewalling. Over time, crew members start shifting their sleep schedules, some staying up late and others waking early, just to carve out a few hours alone.
A Mars mission would last roughly three years. The communication delay with Earth would reach up to 24 minutes each way, making real-time conversation with mission control or family impossible. Crews would need to be largely self-reliant, both technically and emotionally. No current selection or training process has been validated for that duration and level of isolation.
Settling Another World
Visiting Mars and living on Mars are fundamentally different challenges. A visit requires keeping a small crew alive in a sealed habitat for a defined period. A settlement requires food production, construction, medical care, governance, and eventually the ability to sustain a population without constant resupply from Earth. None of these systems exist yet, even in prototype form, for off-world use.
The most realistic near-term scenario is a series of increasingly long crewed missions to the Moon through the 2030s, followed by the first human Mars landing sometime in the 2040s or 2050s. Whether those visits evolve into permanent habitation depends on solving the bone loss, radiation, and reproduction problems, and on whether the political and economic will survives across decades of expensive, incremental progress.
Beyond the Solar System
Reaching another star is a problem of an entirely different scale. Alpha Centauri, the nearest star system, is 4.37 light years away, about 25 trillion miles. With today’s fastest spacecraft, the trip would take roughly 30,000 years.
The most serious attempt to change that math is Breakthrough Starshot, a $100 million research program exploring whether tiny, gram-scale probes pushed by ground-based lasers could reach 20% of the speed of light. At that velocity, a probe could reach Alpha Centauri in about 20 years. But these would be flyby missions for data collection, not transport for humans. Sending people to another star system would require propulsion technology, life support, and social structures that don’t exist even in theory yet.
So will humans ever leave Earth? We already do, temporarily. We’ll almost certainly return to the Moon within the next few years and reach Mars within a generation. Living permanently on another world is plausible but faces deep biological barriers that engineering alone can’t solve. And reaching the stars with human passengers remains, for now, a challenge so vast it belongs to a future we can barely sketch.