A Possible Shortcut To Mars Could Cut The Round Trip By More Than Half

One possible option could see humans reach Mars in just 33 days.

A crewed expedition to Mars promises to push the absolute limits of human endurance. To grasp the sheer scale of the journey, consider our recent return to the Moon. When the Artemis II spacecraft crossed the lunar void, it traversed roughly 380,000 kilometers of deep space. The mission took 10 days.

A crew bound for the Red Planet, however, must launch during a narrow window when Mars swings closest to Earth. Yet even at this absolute nearest point, they face an astonishing 55-million-kilometer voyage—roughly 145 times further than a trip to the Moon. Not to mention that spacecraft trajectories are never plotted in straight lines.

A new study asks a different question. What if the fastest route to Mars is not found by looking only at Earth and Mars, but by studying the messy first orbital estimates of a nearby asteroid?

That is what astronomer Marcelo de Oliveira Souza did. He treated the early orbit of a near-Earth asteroid not as a place to visit, but as a kind of guide line through space. The result is a possible fast route that could cut a Mars round trip to less than half the usual time.

It is an unusual idea. But it suggests that some of the solar system’s best shortcuts may be hiding in the discarded first drafts of asteroid tracking data.

The Goldilocks Distance

The distance between Earth and Mars constantly stretches and compresses as they race around the Sun at different paths and velocities.

Engineers target a narrow window that opens roughly every 26 months. During this alignment, known as Mars opposition, Earth slides directly between the Sun and Mars. The two planets sit on the same side of our host star, bringing them relatively close together.

Even with this head start, a conventional, direct one-way flight takes anywhere from 7 to 10 months.

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Marcelo de Oliveira Souza, an astronomer at the State University of Northern Rio de Janeiro, suspected that standard planetary calculations were missing something vital. He wondered if the solar system contained unseen corridors that temporarily opened during these close approaches.

To find them, Souza turned his attention away from the planets and toward the rubble drifting between them.

The Mathematical Ghost

When astronomers first spot a near-Earth asteroid, they quickly track its motion across the sky to calculate a preliminary orbit. These initial approximations often reveal highly eccentric, sweeping trajectories with a distinct tilt relative to the plane containing Earth’s orbit around the Sun.

Scientists eventually refine these paths with further observations, often tossing the early orbital data aside. Souza, however, realized these rough sketches possessed immense value.

He focused on asteroid 2001 CA21. Its preliminary 2015 orbital prediction crossed the paths of both Earth and Mars. Souza used its highly eccentric orbit as a pure geometric template.

The researcher searched for a flight path to Mars that stayed within five degrees of the asteroid’s specific tilt. Sticking strictly to this angle would allow a spacecraft to carve a radically direct path through space.

He then tested this geometric constraint against three upcoming Mars oppositions: 2027, 2029, and 2031.

The 2031 Sweet Spot

To be entirely clear, the researchers are not proposing to use the asteroid as a gravitational slingshot, primarily because a space rock like 2001 CA21 lacks the massive bulk required to physically whip a spacecraft toward another planet. Instead, their discovery showed that the asteroid’s highly tilted, invisible orbital path left behind a geometric “fast lane” through the void that engineers could, in principle, design a spacecraft trajectory around.

The first two launch windows proved to be dead ends. The planetary alignments in 2027 and 2029 failed to match the asteroid’s favorable geometry.

A spacecraft attempting these routes would face immense energetic hurdles. More critically, the ship would arrive at Mars moving far too fast for current braking technology to handle safely. The geometry also failed to support a symmetrical, immediate return trip to Earth.

The 2031 alignment, however, worked.

During this specific window, the Earth-Mars geometry synchronized with the asteroid’s orbital plane. Souza discovered two complete, dynamically sound round-trip profiles for a spacecraft.

The first option is an ultra-rapid, high-energy flight completing the entire mission in roughly 153 days. This includes a blistering 33-day outbound flight, a 30-day stay on the Martian surface, and a 90-day return journey.

The second option offers a more feasible, lower-energy path taking 226 days. A crew would spend 56 days flying out, 35 days on the ground, and 135 days coming home.

“The 2031 Mars opposition supports two complete sub-year round-trip missions consistent with the CA21-anchored plane, illustrating how early small-body orbital data may contribute to the early identification of rapid interplanetary transfer opportunities,” Souza explained in his paper.

A New Cosmic Cartography

This research shifts how space agencies might navigate the solar system. Future missions do not need to follow asteroid 2001 CA21 specifically. Instead, the study demonstrates a potentially useful new concept.

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Astronomers constantly monitor the skies for space rocks, primarily to protect our planet from catastrophic impacts. Now, that same surveillance data can double as a deep space navigation tool.

The raw, unrefined tracking data of an asteroid can expose orbital shortcuts that traditional, energy-based planetary models easily overlook.

“This study illustrates how the well-defined plane geometry of a preliminary small-body orbit can be employed as a methodological screening tool for rapid interplanetary transfer identification,” Souza noted.

By sifting through the sweeping paths of near-Earth objects, engineers hold a new key to the solar system. They can finally chart the rapid, reversible routes required to explore deep space without demanding astronauts spend years in the dark.

The study was published in the journal Acta Astronautica.