A Brazilian cosmologist studying near-Earth asteroids wasn’t looking for a shortcut to Mars — but he found one anyway. Marcelo de Oliveira Souza noticed that early, imprecise orbital estimates of certain asteroids, data typically discarded once better measurements arrive, appeared to trace faster geometric paths between Earth and Mars.
His findings, published in Acta Astronautica, suggest a round trip to the Red Planet could someday take as little as five months — compared to the nearly three years current mission profiles require. The catch: knowing the route exists is a very different problem from getting there that fast.
An asteroid’s ghost trajectory
Souza’s accidental discovery began with a single asteroid. In 2015, while studying near-Earth asteroid 2001 CA21, he noticed something unusual: the object’s early, rough orbital estimates traced a rare path crossing both Earth’s and Mars’ orbital zones. It wasn’t the asteroid’s actual trajectory — just the preliminary geometry before more precise observations arrived to correct it.
That distinction matters. As astronomers gather more data, early orbital estimates get revised and then discarded. By the time Souza examined 2001 CA21’s refined path, the original geometric clue had effectively vanished from the record. The October 2020 opposition — when Earth and Mars aligned on the same side of the sun — made that fleeting early geometry particularly striking, hinting at unusually short routes between the two planets.
“This was a surprise for me — I was not looking for this,” Souza told Live Science. He acknowledged that someone analyzing the same asteroid at a different point in time simply wouldn’t have seen what he saw. “Maybe I was in the right place at the right time,” he said.
From geometry to mission timelines
Inspired by the asteroid’s early orbital plane, Souza applied Lambert analysis — a standard method for calculating paths between two points in space — to explore whether similar geometry could support fast human missions during upcoming Mars oppositions in 2027, 2029, and 2031.
Only the 2031 window produced a viable result. According to his calculations, a spacecraft departing Earth on April 20, 2031, could reach Mars in just 33 days, spend approximately 30 days on the surface, depart June 22, and return to Earth by September 20 — a complete round trip of 153 days, or roughly five months.
Souza also identified a lower-energy option within the same window. That alternative would require a launch speed of about 16.5 km/s and result in a total mission duration of roughly 226 days — about seven and a half months. Even that slower version would represent a substantial improvement over the current baseline of nearly three years.
The speed problem
The faster trajectory comes with requirements no existing technology can meet. Departure speeds of approximately 32.5 km/s would be necessary, and a spacecraft would arrive at Mars traveling at around 108,000 km/h — far beyond what current landing systems can handle safely.
Even the lower-energy alternative pushes hard against what’s been achieved. For comparison, NASA’s New Horizons probe launched in 2006 at 16.26 km/s, making it the fastest human-made object ever launched from Earth at the time. The more conservative version of Souza’s proposed trajectory would demand comparable speeds just to stay on the slower path.
Next-generation launch systems could potentially close some of that gap. Souza pointed to SpaceX’s Starship and Blue Origin’s New Glenn as candidates that might approach the required velocities — but spacecraft design, payload mass, and propulsion architecture would all need to align, and none of those variables are resolved.
A new tool, not yet a mission plan
Souza is careful about what his findings actually represent. The concept remains largely theoretical, dependent on mission-specific factors his calculations don’t address. No spacecraft has been designed for these trajectories, and the propulsion technology needed for the faster options simply doesn’t exist yet.
The method still carries real value. By narrowing the search space for viable fast-transfer windows, it gives mission planners a new way to identify candidate opportunities — even if any actual mission would require substantial additional work.
Perhaps more intriguingly, the approach reframes something the scientific community routinely discards. Preliminary orbital estimates have always been treated as noise, useful only until better data replaces them. Souza’s work suggests they may contain geometric information worth preserving, at least temporarily, as a navigational resource.
Whether the 2031 window becomes a serious target depends on how quickly propulsion technology advances over the next several years. Souza’s findings don’t define a mission — but they may have identified the right moment to attempt one, if the hardware ever catches up.