Mars transfer window — next departure
Spacecraft cannot leave for Mars at will — they depart only during windows that recur about every 26 months, when the two planets line up. The November–December 2026 window is effectively empty after SpaceX said in February 2026 that Mars would be deprioritised for five to seven years in favour of the Moon; the next opportunity is late 2028 to early 2029. No launch is currently scheduled.
📍 Visible from where you are right now — computed in your browser
bearing · altitude · rise time · best time tonight
The moment of Mars transfer window — next departure: https://nowsky.org/e/mars-transfer-window-2028 — opens at the right place and time, replayable, no login.
Available views: Orbit ✓ · Sky — (not visible in the sky)
The story
Earth and Mars draw close about once every 26 months. Leave during that "transfer window" and a spacecraft reaches Mars on the least fuel — a Hohmann transfer, an ellipse that sweeps half-way round the Sun. The window opens between December 2028 and January 2029; miss it and the next is early 2031.
The physics is simple. Earth orbits in 365 days, Mars in 687, so Earth laps Mars every 780 days (the synodic period). The minimum-energy path only works when the two planets stand at a fixed angle at departure, which is why Mars launches bunch into a few weeks and a miss costs two years.
The November–December 2026 window is effectively empty after SpaceX said in February 2026 that Mars would be deprioritised for five to seven years in favour of the Moon. Aimed at the late-2028 window are ESA's Rosalind Franklin rover (ExoMars) and China's Tianwen-3 sample-return mission; the timing of any cargo Starship to Mars is undecided.
"When do humans go to Mars?" is ultimately answered by the list of these windows. Move the orbit view to December 2028 and the positions of Earth and Mars show at a glance why that moment is a window — follow Mars and Earth can be seen closing on it from the inner orbit.
Why it matters
The transfer window is the calendar of Mars exploration. Rovers, orbiters and crewed plans all budget and schedule to this 26-month rhythm, and a slip pushes a whole mission back two years — as happened when the Rosalind Franklin rover missed 2022 and moved to 2028.
For crews the window matters more still: seven to nine months out, about fifteen months waiting on Mars for the next return window, seven to nine months back — a two-and-a-half-year round trip fixed by orbital mechanics. Faster trajectories demand exponentially more fuel.
Windows also differ in quality. Because Mars's orbit is eccentric, the closest approach varies from 56 million km (2003) to over 100 million km, and 2028–2029 rates as middling — which is why the mass a given rocket can deliver changes from window to window.
How to watch
A transfer window is a calendar event more than a sky event, but as it opens Mars is closing on Earth and brightening noticeably — around opposition in March 2029 it shines at magnitude −1 as a red star due south at midnight.
Move the orbit view to 20 December 2028 and follow Mars: the layout shows Earth on the inner orbit just before it overtakes. Speed up the playback and the same configuration repeats every 26 months.
Select Mars in the sky view for its rise time, altitude and 24-hour track from your location. In the winter the window opens, it rises in the east in the evening and stays up until dawn.
See this for yourself — replay the moment in the orbit view
Background
The Hohmann transfer is the minimum-energy orbit computed by Walter Hohmann in 1925. Real missions fly slightly faster "Type I" trajectories for arrival speed and communications, but the window sits in the same place. Mariner 4 (1964), Viking (1975), Curiosity (2011) and Perseverance (2020) all left through it.
The July 2020 window carried three missions — Perseverance, Tianwen-1 and the UAE's Hope — a "Mars fleet"; 2022 emptied when Rosalind Franklin lost its Russian lander; SpaceX pushed from October 2024 to 2026, and 2026 in turn went effectively unused.
Ways around the window are studied — nuclear thermal or solar-electric propulsion promise wider windows and shorter flights — but none has yet flown a Mars mission. Until then, the Martian calendar runs on 26 months.
The roughly 26-month spacing of Mars transfer windows is the synodic period (780 days) that follows from the orbital periods of Earth (365 days) and Mars (687). Not every window is equal: because of the eccentricity of Mars’s orbit, windows when Mars is near perihelion (2033, 2035) need a smaller change in velocity, and those near aphelion (late 2028) a larger one. The payload a given rocket can send therefore differs from window to window, and the 2028 window is somewhat less favourable than 2026. Such differences are why mission planners aim for particular windows.
FAQ
Why can't we leave for Mars any time?
The minimum-fuel trajectory needs Earth and Mars at a fixed relative angle at departure, and that configuration recurs only every 26 months or so.
How long does the trip take?
Seven to nine months on a Hohmann transfer; a crewed round trip is about two and a half years including the wait on Mars.
Are any missions planned for the 2028 window?
ESA's Rosalind Franklin rover and China's Tianwen-3 target this window; a Starship flight to Mars is undecided.
When is the window after this one?
Early 2031, then spring 2033.
Related
- ExoMars — Rosalind Franklin launch
- Tianwen-3 launch — Mars sample return
- MMX launch — Phobos sample return
- Perseverance launch
- Mars — object index
Times and figures are approximate — verify with official sources when planning travel. Simulation uses J2000 mean elements.