Perhaps this can change the idea that we need more than two years
For generations, the journey to Mars has been defined not merely by distance, but by the slow choreography of two planets orbiting the sun—a geometry that has made any crewed mission a years-long undertaking. Now, a Brazilian cosmologist named Marcelo de Oliveira Souza has found, almost by accident, a theoretical orbital path that could compress a round-trip Mars mission to just 153 days by 2031. His discovery emerged not from a deliberate search, but from a discarded asteroid estimate that contained, hidden within its imprecision, a glimpse of something faster. The cosmos, it seems, sometimes reveals its shortcuts only to those who are paying attention to the wrong thing.
- The tyranny of orbital mechanics has long condemned Mars-bound astronauts to nearly three years away from Earth—months of travel, months of waiting, months of return.
- A routine asteroid survey in 2015 produced a calculation that was technically incorrect, yet cosmologist Marcelo de Oliveira Souza recognized in its error a rare and valuable geometry.
- Applying Lambert analysis to a narrow orbital inclination, Souza identified a 2031 window that could carry a spacecraft from Earth to Mars in just 33 days at speeds of 27 kilometers per second.
- Next-generation rockets like SpaceX's Starship and Blue Origin's New Glenn sit at the edge of the velocities required, making the physics plausible even as the engineering remains unproven.
- Published in Acta Astronautica, the findings reframe how discarded preliminary asteroid data might be mined for interplanetary navigation—turning astronomical noise into potential roadmaps.
Getting to Mars has always been a problem of patience. The planet averages 225 million kilometers away, and even after a five-to-eleven-month journey, arriving astronauts cannot simply turn around. They must wait for the planets to realign—a window that opens only every 26 months—meaning a full crewed mission stretches to nearly three years of travel, surface time, and return.
In 2015, Brazilian cosmologist Marcelo de Oliveira Souza was cataloguing near-Earth asteroids when he noticed something unusual in the preliminary orbital data for asteroid 2001 CA21. Its early estimated path swung close to both Earth's and Mars's orbits along a plane tilted just five degrees from the standard reference. Souza wasn't searching for a shortcut to Mars—but he recognized a possibility hiding inside a calculation that would later be corrected and discarded.
Using Lambert analysis and restricting his search to that unusual orbital inclination, Souza examined upcoming Mars oppositions and found that only the 2031 alignment offered the right geometry for an exceptionally fast transfer. His results, published in Acta Astronautica, describe a mission departing Earth on April 20, 2031, reaching Mars in just 33 days, spending roughly a month on the surface, and returning by late September—153 days total.
The required velocity of 27 kilometers per second is extreme but not physically impossible. NASA's New Horizons probe launched at 16 km/s in 2006; next-generation vehicles like SpaceX's Starship or Blue Origin's New Glenn could theoretically reach the speeds Souza's model demands. Still, the concept remains theoretical, contingent on engineering solutions that do not yet exist.
What makes the discovery quietly significant is its method: preliminary asteroid orbits, long treated as rough drafts to be refined and forgotten, may hold within their imprecision the outlines of faster routes between worlds. 'Perhaps this can change the idea that we need more than two years to go to Mars and come back,' Souza said. The 153-day mission is still a hypothesis—but it suggests the long wait imposed by orbital geometry may not be permanent.
Getting to Mars has always been a problem of patience. The planet sits roughly 225 million kilometers away on average, and with current rocket technology, the journey takes somewhere between five and eleven months just to get there. But that's only half the story. Once astronauts arrive, they can't simply turn around and come home. They have to wait for the planets to align properly—a window that opens only every 26 months or so, during what astronomers call Mars oppositions. This means a crewed mission to Mars, as currently planned, would stretch to nearly three years. The astronauts would spend months traveling, months on the surface, and months traveling back, all because of the geometry of two orbiting worlds.
In 2015, a Brazilian cosmologist named Marcelo de Oliveira Souza was studying near-Earth asteroids when he noticed something odd. One asteroid, designated 2001 CA21, had preliminary orbital estimates that showed an unusual path—one that could swing close to Earth's orbit and then close to Mars's orbit, all within a plane tilted just five degrees from the standard reference. Souza wasn't looking for a shortcut to Mars. He was mapping asteroids. But he saw something in those early calculations, before they were refined by better observations. He saw a possibility.
The asteroid's initial orbit was technically wrong. As astronomers gathered more data, the real path of 2001 CA21 became clearer, and the preliminary estimates were discarded. But Souza realized those "wrong" estimates contained something valuable: a theoretical configuration that could enable fast transfers between Earth and Mars. "I was in the right place at the right time," he later said, though he wasn't looking for what he found.
Using a standard mathematical method called Lambert analysis, Souza restricted his calculations to orbital paths within five degrees of the asteroid's unusual inclination. He then examined the Mars oppositions scheduled for 2027, 2029, and 2031. Only the 2031 alignment offered the right geometry for an extremely fast transfer. The results, published in the journal Acta Astronautica, were striking. According to Souza's calculations, a spacecraft could depart Earth on April 20, 2031, arrive at Mars on May 23 after just 33 days of travel, spend about 30 days on the surface, and return on September 20. Total mission time: 153 days. A slightly less demanding alternative would take 226 days.
These speeds are extreme—about 27 kilometers per second for the fastest option—but not unprecedented. NASA's New Horizons probe was launched at 16.26 kilometers per second in 2006 and reached Pluto. Next-generation rockets like SpaceX's Starship and Blue Origin's New Glenn could potentially achieve the velocities Souza's calculations require. The physics is sound. The engineering is another question entirely.
For now, this remains theoretical. Whether such a route could actually be used depends on countless technical factors: the weight of the spacecraft, the efficiency of its engines, the ability to navigate with precision across millions of kilometers. No one has built a ship that could handle these speeds and still land safely on Mars. But Souza's discovery opens a new way of thinking about the problem. Preliminary asteroid orbits—historically used to assess impact risks and then filed away—might help identify faster paths between planets. "Perhaps this can change the idea that we need more than two years to go to Mars and come back," Souza said. The 153-day mission remains a theoretical exercise, but it suggests that the long wait between Earth and Mars might not be as inevitable as we thought.
Notable Quotes
This was a surprise to me; I wasn't looking for this— Marcelo de Oliveira Souza, on discovering the orbital pattern
Perhaps this can change the idea that we need more than two years to go to Mars and come back— Marcelo de Oliveira Souza, on the implications of his findings
The Hearth Conversation Another angle on the story
How does someone accidentally discover a shortcut to Mars while studying asteroids?
Souza was mapping near-Earth asteroids in 2015 when he noticed one with preliminary orbital estimates that showed an unusual path—it could swing near both Earth and Mars. Those early estimates were technically wrong, but he saw something useful in them: a theoretical configuration that could enable fast transfers.
So the asteroid's real orbit is different from what he used?
Exactly. As more observations came in, the actual orbit of asteroid 2001 CA21 was refined, and the preliminary estimates were discarded. But Souza realized those "wrong" estimates contained a valuable pattern—a geometry that could work for interplanetary travel.
Why does the 2031 opposition specifically work when 2027 and 2029 don't?
It's about planetary geometry. Souza used Lambert analysis to calculate transfer paths within five degrees of the asteroid's unusual inclination. Only the 2031 alignment offered the right spatial configuration for an extremely fast transfer. The other years didn't have that particular alignment.
33 days to Mars sounds almost too fast. What's the catch?
The speeds required are extreme—27 kilometers per second. That's faster than anything we've sent to Mars before. SpaceX's Starship and Blue Origin's New Glenn might be able to reach those velocities, but we've never actually landed a spacecraft at those speeds on Mars. The engineering challenges are enormous.
Is this actually going to happen in 2031?
Almost certainly not. This is a theoretical calculation showing what's geometrically possible. Whether it can actually be done depends on whether we can build rockets fast enough, land them safely, and navigate with the precision required. Souza himself emphasizes this is still in the realm of models and simulations.
What makes this discovery significant if it might never be used?
It changes how we think about Mars travel. For decades, we've accepted that missions take years because of orbital mechanics. Souza showed that's not inevitable—there are windows, rare ones, where the geometry allows something much faster. That opens a new way of searching for efficient routes.