Astronauts could complete a round trip to Mars in less than a year someday, potentially cutting current mission timelines in half, according to a new study that drew inspiration from asteroid trajectories.

Under current mission profiles, reaching Mars, which is located about 50% farther from the sun than Earth is, takes roughly seven to 10 months. Because Earth and Mars align for fuel-efficient transfers only every 26 months, astronauts must wait for a return window, stretching a full round trip to nearly three years.

However, the new findings, published online in the journal Acta Astronautica in April, suggest that early, imprecise orbital estimates of near-Earth asteroids — which were historically used to assess impact risks, before being discarded in favor of more precise data — may contain valuable geometric clues for designing faster interplanetary routes.

"Maybe this can change the idea that we need more than two years to go to Mars and return," study author Marcelo de Oliveira Souza, a cosmologist at the State University of Northern Rio de Janeiro in Brazil, told Live Science.

"I was not looking for this"
Souza first stumbled on the idea in 2015, when he was studying near-Earth asteroids. One object in particular, 2001 CA21, caught his attention because early estimates suggested it followed a rare path crossing both Earth's and Mars' orbital zones.

Although later measurements refined the asteroid's true trajectory, its initial geometry during the October 2020 opposition — when Earth and Mars were aligned on the same side of the sun, and closest together in their orbits — hinted at the possibility of "ultra-short" routes between the two planets, Souza noted in the paper.

"This was a surprise for me — I was not looking for this," he told Live Science.

As more observations allow astronomers to refine an asteroid's orbit, those early trajectories change, so someone analyzing it later wouldn't have seen the same path, Souza added. "Maybe I was in the right place at the right time," he said.

Round trip to Mars?
For the October 2020 opposition, Souza's calculations showed that a very fast, roughly 34-day trip from Earth to Mars is geometrically possible if a spacecraft follows a path similar to the asteroid's early orbital plane.

However, such a trajectory would require departure speeds of around 32.5 kilometers per second, well beyond current rocket capabilities, and a spacecraft would arrive at Mars traveling around 64,800 mph (108,000 km/h) — too fast for existing landing systems to handle safely, Souza noted in the paper.

Instead, Souza used the asteroid-inspired geometry to explore possible trips during future Mars oppositions in 2027, 2029 and 2031. By using a standard method for calculating paths between two points in space (called the Lambert analysis) and constraining those paths to remain within about 5 degrees of the asteroid's orbital tilt, Souza found that only the 2031 alignment offered a viable opportunity for rapid travel using near-term technology.

In that window, a round-trip mission from Earth to Mars could be completed in just 153 days, or roughly five months, according to the study.

In that scenario, a spacecraft would depart Earth on April 20, 2031, at about 27 kilometers per second, arrive at Mars by May 23 after a 33-day journey, spend about 30 days on the surface, depart June 22 and return to Earth by Sept. 20, with the return leg taking roughly 90 days.

Souza also identified a lower-energy alternative within the same window, requiring a launch at about 16.5 kilometers per second for a mission lasting about 226 days, or about 7.5 months ‪—‬ still significantly shorter than current mission timelines.

Still, the concept remains largely theoretical and would depend heavily on mission specifics — including spacecraft design, payload mass and propulsion capabilities — all of which would shape whether such fast transfers are feasible in practice.

The method, however, could still prove useful as a way to narrow the search for viable trajectories. The required velocities are comparable to those achieved by missions such as New Horizons — the NASA probe, which, when launched in 2006 on a mission to flyby Pluto at 16.26 kilometers per second, was the fastest human-made object ever launched from Earth.

Such high-speed trajectories could be within the reach of next-generation rockets such as SpaceX's Starship or Blue Origin's New Glenn, Souza told Live Science.