Have you ever looked up at Mars in the night sky — that faint, rust-colored dot — and wondered: just how far away is it, really? Not in light-years. Not in some abstract cosmic sense. But in months of your life, sealed inside a spacecraft, hurtling through absolute emptiness.
Welcome, dear FreeAstroScience reader. I'm Gerd Dani — astronomer, physicist, wheelchair user, and president of Free Astroscience - Science and Cultural Group. Here, we believe that science belongs to everyone. We explain complex ideas in plain words, because knowledge should never be locked behind a wall of jargon. As we always say: keep your mind active at all times — the sleep of reason breeds monsters.
In this post, we're going to walk you through every phase of the most ambitious journey humans have ever planned: the trip to Mars. We'll talk real numbers, real risks, and real hopes. Stick with us until the end — there's more to this story than you might expect.
The Red Planet Calls: A 9-Month Odyssey Through the Solar System
How Far Is Mars, Exactly?
This is where the story starts getting strange. Mars is not a fixed destination. It's a moving target — and a pretty erratic one at that. Both Earth and Mars orbit the Sun, but at different speeds and along slightly different paths. That means the gap between us can shift dramatically depending on where each planet is in its orbit.
According to NASA, the Earth–Mars distance swings between 56 million kilometres at its closest (a rare event called perihelic opposition) all the way out to 400 million kilometres when the two planets are on opposite sides of the Sun. The average sits around 230 million kilometres.
| Scenario | Distance (km) | Distance (AU) | Status |
|---|---|---|---|
| Closest approach (opposition) | ~56,000,000 | ~0.37 AU | Best launch window |
| Average distance | ~230,000,000 | ~1.53 AU | Typical planning baseline |
| Farthest apart | ~400,000,000 | ~2.67 AU | Never launch here |
Those numbers explain why mission planners don't just "pick a date." Everything depends on timing — and those rare windows of opportunity determine whether a mission is even feasible in a given year.
How Long Does It Really Take to Travel to Mars?
Here's the short answer: roughly 9 months with today's technology, for a crewed spacecraft. But the real picture is more nuanced than that single number suggests.
NASA's Goddard Space Flight Center puts the one-way travel time at approximately nine months using current propulsion systems. Uncrewed probes sent so far have taken anywhere from 128 to 333 days to reach Mars — that's a gap of over six months, depending on the mission profile and launch timing.
Prof. Craig Patten of the University of California, San Diego, points out that we could shorten the trip by burning more fuel to accelerate the spacecraft continuously. The problem? Fuel is heavy. Every kilogram of extra propellant is a kilogram you can't use for food, water, medical supplies, or scientific equipment. There's always a trade-off.
Why Don't We Just Fly in a Straight Line?
Think of it like trying to throw a ball to a friend running across a field. You don't aim at where they are — you aim at where they'll be by the time the ball gets there. Mars works the same way.
Spacecraft headed to Mars follow what's called a Hohmann Transfer Orbit — an elegant elliptical path first described by German engineer Walter Hohmann back in 1925. It's not the shortest route, and it's certainly not the fastest. But it's the most fuel-efficient, and in space, fuel efficiency isn't just economical — it's a matter of survival.
Ttransfer = half-period of the transfer ellipse (travel time Earth → Mars)
a = semi-major axis of transfer orbit = (rEarth + rMars) / 2 ≈ 1.26 AU
G = gravitational constant (6.674 × 10⁻¹¹ N·m²/kg²)
M☉ = mass of the Sun (1.989 × 10³⁰ kg)
Result: Ttransfer ≈ 259 days (~8.6 months)
The Hohmann path takes a spacecraft from Earth's orbit out to Mars in roughly 260 days. Two engine burns are needed: one to leave Earth's orbit, and another to slow down enough for Mars to capture the spacecraft gravitationally. Miss either burn, and the craft drifts off into the void — there's no pulling over to check the map.
Critically, launch windows for this optimal trajectory open only every 26 months, when Earth and Mars align just right. Miss that window, and you wait another two years. That's why every Mars mission in history has been planned years in advance around those narrow calendar slots.
What Have Past Robotic Missions Told Us?
Since the early 1960s, space agencies have been sending robotic scouts to Mars. Those missions gave us not just data about the Red Planet — they also gave us our best benchmarks for travel times.
| Mission | Agency | Launch Year | Travel Time | Type |
|---|---|---|---|---|
| Mars Odyssey | NASA | 2001 | ~200 days | Orbiter |
| Mars Reconnaissance Orbiter | NASA | 2005 | ~7.5 months | Orbiter |
| MAVEN | NASA | 2013 | ~10 months | Orbiter |
| InSight | NASA | 2018 | ~6.5 months | Lander |
| Perseverance | NASA | 2020 | ~7 months | Rover |
| Uncrewed range (all missions) | Various | 1960s–present | 128–333 days | All types |
More than four decades of orbital data, surface photographs, and soil chemistry results have brought us to a point where we know Mars better than almost any other place in the solar system — apart from Earth itself. And yet, no human has set foot there. Not yet.
Can We Get There Faster? SpaceX Says Yes.
SpaceX's ambitious Starship vehicle could, according to some researchers, cut the one-way journey to just over 90 days. A 2025 study published in Nature Scientific Reports by a University of California, Santa Barbara physicist identified two specific trajectories — each under 104 days — that Starship could theoretically follow, enabled by orbital refueling and aerocapture at Mars.
The trick is refueling in orbit. Instead of launching with all the fuel you'll ever need (which is physically impossible at the scale required), Starship would top up its tanks in Earth orbit before heading out. That extra propellant translates directly into higher velocity, shortening the trip considerably. On arrival, aerocapture — using Mars's thin atmosphere to slow down instead of burning fuel — saves even more propellant.
For the return trip, the plan gets even bolder. Starship would need to manufacture its own propellant on Mars — a process called In-Situ Resource Utilisation (ISRU). By splitting water ice (H₂O) and carbon dioxide (CO₂) found on the Martian surface, the craft could produce liquid methane and liquid oxygen for the engines. The roughly 18 months spent on Mars waiting for the next launch window would provide enough time to complete this production. Tight, but mathematically sound.
Elon Musk has stated there's a 50/50 chance of launching the first uncrewed Starship to Mars as early as late 2026, taking advantage of the next favorable Earth–Mars alignment.
What Are the 14 Challenges Astronauts Will Face?
Getting to Mars isn't just a physics problem. It's a human problem — one that researchers Biswal and Annavarapu tackled head-on in a paper accepted for publication in Advances in Aeronautical Sciences. They identified 14 distinct challenges that any crewed Mars mission must address. Here are the key ones:
What's striking about Biswal and Annavarapu's analysis is the degree of overlap between these challenges. Radiation affects psychology. Distance affects supply chains. Microgravity affects the ability to perform medical procedures. You can't solve one without thinking about all the others. It's not a checklist — it's a web.
How Deadly Is the Radiation Out There?
This one deserves its own section — because the numbers are sobering. On Earth, the average person absorbs about 0.17 mSv of radiation per day (roughly 62 mSv per year), from natural and medical sources combined. In deep space, that number changes dramatically.
| Environment | Daily Dose (mSv/day) | Multiplier vs. Earth | Mission Subtotal |
|---|---|---|---|
| Earth (average person) | 0.17 mSv | 1× (baseline) | ~62 mSv/year |
| In transit to/from Mars | 1.64 mSv | 9.5× | ~600 mSv (1-year round trip) |
| On Mars surface | 0.73 mSv | 4.3× | ~400 mSv (18-month stay) |
| Total Mars mission (2.5 yrs) | — | — | ~1,000 mSv |
That total of 1,000 mSv over a 2.5-year mission is roughly 16 times what you'd absorb living an ordinary life on Earth over the same period. It significantly raises the lifetime risk of cancer and can cause damage to the central nervous system — effects we're still studying.
Underground Habitats: Mars's Best Shield
One of the most promising solutions comes from Biswal himself: "We're developing an underground Martian habitat that could address all health issues during a long mission or a permanent settlement on Mars." Digging into the Martian regolite — the loose rock and soil covering the surface — provides natural shielding against both solar particle events and galactic cosmic rays. Local water ice, once melted and used to create thick water-wall barriers, adds another layer of protection. It's low-tech, but it works.
Could Nuclear Rockets Change Everything?
The answer is almost certainly yes — and NASA knows it. Nuclear propulsion has been on engineers' wish lists since the Cold War era, when NASA developed the NERVA (Nuclear Engine for Rocket Vehicle Application) concept. More recently, NASA and DARPA have been testing the DRACO (Demonstration Rocket for Agile Cislunar Operations) program, while Ad Astra's VASIMR engine represents a plasma-based electric alternative.
| Propulsion Type | Estimated Travel Time | Key Advantage | Main Challenge |
|---|---|---|---|
| Chemical (Hohmann — current standard) | ~260 days (8–9 months) | Proven, reliable technology | Long exposure to radiation & microgravity |
| SpaceX Starship (orbital refueling) | 90–104 days | Within NASA radiation limits; no new propulsion needed | Requires large-scale orbital refueling infrastructure |
| Nuclear Thermal (NTP/NTR) | ~100 days | High thrust, very efficient fuel use | Nuclear safety concerns, regulatory hurdles |
| Nuclear Electric (NEP / VASIMR) | 90–120 days | Extremely fuel-efficient for long missions | Low thrust; requires long acceleration phases |
A spacecraft equipped with nuclear thermal propulsion could reach Mars in roughly 100 days — cutting nearly two months off the standard chemical-rocket journey. The physics is compelling: 1 kilogram of uranium-235 holds the same energy as roughly 3 million kilograms of conventional rocket fuel. The engineering challenges, though, are real. Nuclear systems demand extraordinary safety protocols, and no one yet wants to launch a fission reactor from Earth's surface if it risks contaminating the atmosphere on a launch failure.
The elegant middle path — the one researchers like Kingdon at UC Santa Barbara are pointing to — is using Starship's chemical propulsion with smarter trajectories. No new physics required. Just better math, orbital refueling, and a willingness to accelerate harder on departure. Sometimes the elegant solution is the one hiding in plain sight.
What Will Astronauts Actually Do on Mars?
After a 9-month journey and an 18-month stay, you'd want to keep busy — and Mars will keep every astronaut more than occupied. The planet, after all, is the second most habitable place in the Solar System by Earth standards, and decades of robotic exploration have shown it may once have supported liquid water and possibly life.
Here's what the science agenda looks like for those first human visitors:
- 📍 Geological surveys: mapping rock formations, studying stratigraphy, and collecting soil samples for analysis in a Martian field lab — and eventually shipping them back to Earth
- 💧 Water ice hunting: locating, extracting, and testing subsurface ice deposits — critical both for drinking water and for fuel production
- 🔬 Life detection experiments: searching for biosignatures, past or present, in soil, rock, and the thin Martian atmosphere
- ⚗️ ISRU (In-Situ Resource Utilisation) tests: converting H₂O and CO₂ into oxygen, hydrogen, and rocket propellant on-site
- 🌿 Controlled agriculture: growing edible plants in pressurised enclosures under Mars's 1/3 Earth gravity — a genuine test of long-term human survival
- 🧬 Human physiology research: studying how the body adapts — or doesn't — to living in reduced gravity for months on end
It's worth being honest about the constraints, too. Even on the surface, astronauts won't simply stroll around. Mars's atmosphere is not breathable — it's 95% CO₂ with a pressure less than 1% of Earth's. Surface temperatures swing wildly, sometimes by 70–80°C in a single day. And without a planetary magnetic field, solar storms could dump dangerous radiation bursts onto the surface with little warning. Every excursion outside the habitat will require full pressure suits and careful real-time monitoring of space weather.
Are We Really Going? And When?
Yes — and the momentum is genuinely building. NASA's five-phase plan for crewed Mars exploration targets human boots on the Red Planet by the mid-2040s, building on the Artemis Moon program as a stepping stone. SpaceX is pushing for a crewed landing by the early 2030s, with colonization potentially following in the 2040s.
Neither timeline is guaranteed. Space exploration has always moved more slowly than anyone hopes — and faster than critics expect. What matters is that the engineering is being done, the science is being studied, and the commitment — from governments, from private companies, and from thousands of scientists and engineers worldwide — is real.
🌌 Final Thoughts
The journey to Mars isn't just about distance or travel time. It's about what we're willing to endure, invent, and risk in the name of curiosity. It's about the 9 months of silence between us and everything we've ever known. It's about the 14 challenges researchers are already solving. It's about the engineers building nuclear engines and orbital fuel stations. And it's about the astronauts who'll one day step onto red soil and look back at a pale blue dot — and know they made it.
Here at FreeAstroScience.com, we believe that understanding a journey like this — every number, every risk, every radical idea — makes us better thinkers and more connected humans. You don't need a physics degree to appreciate the audacity of what we're attempting. You just need to keep your mind wide open.
We'd love to have you back. Come explore more with us at FreeAstroScience.com — where every post is a step further into the universe, explained in plain language, just for you.
📚 Sources
- Zito, M. (2026, March 1). Quanto tempo ci vuole per arrivare su Marte. Reccom.org. https://reccom.org/quanto-tempo-ci-vuole-per-arrivare-su-marte/
- NASA Goddard Space Flight Center. How long does it take to get to Mars? nasa.gov
- Kingdon, R. (2025). 3 months transit time to Mars for human missions using SpaceX Starship. Nature Scientific Reports. DOI: 10.1038/s41598-025-00565-7
- Biswal, A., & Annavarapu, C. S. Challenges for crewed Mars missions. Advances in Aeronautical Sciences.
- Britannica. (2025). Hohmann orbit. britannica.com/science/Hohmann-orbit
- Space.com. How long does it take to get to Mars? space.com
- Phys.org. (2025, June 3). Missions to Mars with Starship could only take three months. phys.org
- Al Jazeera. (2025, May 30). Musk says 50-50 chance of sending uncrewed Starship to Mars by late 2026. aljazeera.com
- Universe Today. (2025). How Long Does it Take to Get to Mars? universetoday.com
- NASA. (2025, February 18). How Long Does it Take to Get to the Moon... Mars... Jupiter. nasa.gov