A Brazilian researcher just found a 153-day route to Mars inside a file that asteroid trackers had already discarded as too rough to use, and it raises a reasonable question about what else is in the bin

A study published in April 2026 in the peer-reviewed journal Acta Astronautica identifies a set of Earth-to-Mars trajectories that could, in principle, cut round-trip mission time to as little as 153 days, against the roughly two to three years current mission profiles require. The author, Marcelo de Oliveira Souza, a cosmologist at the State University of Northern Rio de Janeiro in Brazil, found the geometry by accident while examining the early, since-revised orbital estimate of a near-Earth asteroid, data that is typically discarded once more precise measurements arrive.

Souza is not affiliated with a space agency. “I do not work at a space agency,” he told CNN Brasil. “I am a professor here at the State University of Northern Fluminense… and I achieved a new result that allows for a faster trip to Mars, using the trajectory of an asteroid as a basis.” The work began in 2015 and was, by his own account, unplanned. “This was a surprise for me. I was not looking for this,” he told Live Science.

What the asteroid actually contributed

The asteroid in question, designated 2001 CA21, is not part of the proposed flight path and was never a physical waypoint. In 2015, its early orbital solution described a highly eccentric orbit, with an eccentricity of 0.777 and a perihelion distance of 0.373 astronomical units, on a low-inclination plane that happened to cross the orbital zones of both Earth and Mars. Later observations refined that orbit into a different shape, as they do for most newly spotted asteroids. But the early, since-superseded version left behind something Souza treated as useful on its own terms: a clean geometric plane, unrelated to the asteroid’s actual current path, that could serve as a reference for searching out fast transfer routes between the two planets.

Souza restricted his search for Mars trajectories to routes staying within five degrees of that plane’s tilt, then ran the resulting geometry through a Lambert solver, a standard astrodynamics tool for calculating orbits between two points, across the Mars opposition windows of 2027, 2029, and 2031. Only the 2031 window aligned closely enough with the asteroid-derived plane to produce the fast results. Under that configuration, the study describes two round-trip mission profiles: an “extreme” case combining a 33-day outbound leg with a 90-day return, and a more moderate case pairing a longer outbound leg with a longer return, arriving at a total mission time in the low 200-day range. Reported figures for the second, more conservative case vary somewhat across secondary coverage of the paper; Space Daily has not independently verified the precise day-count breakdown beyond the 153-day headline result Souza has confirmed directly to reporters.

Why nobody is building this rocket yet

The paper is explicit about what it does not attempt. It contains no vehicle engineering, no mass budget, no entry or landing profile, and no thermal analysis. It is a demonstration that a particular mission geometry exists inside real orbital data, not a spacecraft design.

The propulsion requirements for the fastest version of the route are the clearest reason why. Reaching Mars on the 33-day outbound profile would require a departure speed of around 27 kilometres per second — well beyond what any flown propulsion system has achieved for a crewed mission.

For comparison, NASA’s New Horizons probe, the fastest human-made object ever launched at the time of its 2006 departure, left Earth at 16.26 kilometres per second, around 60 percent of the speed the extreme Mars profile would demand. The more moderate configuration eases that requirement somewhat but still sits well outside what any flown propulsion system has achieved. Souza has said the result is a geometric possibility, not a near-term mission plan: “Maybe this can change the idea that we need more than two years to go to Mars and return,” he told Live Science, a statement about the shape of the problem rather than a claim that a ship exists to fly it.

The more interesting question sits underneath the number

The 153-day figure is the number most coverage of Souza’s paper has led with, and it is the more dramatic one. But the finding that carries further is methodological. Early orbital estimates are a routine byproduct of asteroid tracking. Every time a new near-Earth object is spotted, astronomers calculate a preliminary orbit from limited observations, then refine it as more data comes in. The preliminary version is ordinarily treated as a stepping stone with no further use once the refined orbit exists. Souza’s paper treats that preliminary version instead as a resource: a geometric reference plane that can guide a search for efficient transfer routes, independent of whether it represents where the asteroid actually is or was.

That reframing is what raises the broader question. Near-Earth object surveys generate large numbers of early, since-superseded orbital solutions as a matter of routine operation, most of which are set aside once a refined orbit supersedes them. Souza’s method was applied to a single asteroid found, by his description, more by circumstance than by systematic search. Whether the same approach would surface other useful transfer geometries if applied methodically across the wider catalogue of preliminary asteroid orbits is an open question the paper itself does not answer. It is a reasonable one to ask, and one the paper’s own framing invites, but it remains untested at the scale that would settle it.

What to watch next

The 2031 Mars opposition is the only near-term window the paper identifies as aligning with the geometry Souza found, which means the practical test of whether any of this becomes more than a published result is still years away. Whether propulsion systems capable of approaching the speeds the fast configuration requires reach flight readiness in that timeframe, and whether other researchers apply Souza’s method systematically to the broader asteroid catalogue rather than to a single object found by accident, are the two developments most likely to determine whether this result becomes a footnote or a genuine planning tool.