No joking: Get there in as little as 56 days, roundtrips as short as 153
days

https://phys.org/news/2026-04-interplanetary-shortcut-mars.html#google_vignette

and

https://gizmodo.com/astronomer-finds-a-shortcut-to-mars-by-following-an-asteroids-journey-through-space-2000752127

Some quotes:
" In a new study, Marcelo de Oliveira Souza of the State University of Northern Rio de Janeiro followed the predicted route of asteroid 2001
CA21 to look for a new path to reach Mars. The results, published in the journal Acta Astronautica, identify a course that would take
approximately 153 days for a round trip to the Red Planet and back. "

"The paper does not suggest that future missions must follow this
specific asteroid. Instead, it demonstrates a possible way to identify
faster flight paths that traditional methods might miss. "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." "

--- PyGate Linux v1.5.14
* Origin: Dragon's Lair, PyGate NNTP<>Fido Gate (3:633/10)

On 5/3/2026 9:11 AM, Tony Nance wrote:

No joking: Get there in as little as 56 days, roundtrips as short as 153 days

https://phys.org/news/2026-04-interplanetary-shortcut- mars.html#google_vignette

and

https://gizmodo.com/astronomer-finds-a-shortcut-to-mars-by-following-an- asteroids-journey-through-space-2000752127

Some quotes:
" In a new study, Marcelo de Oliveira Souza of the State University of Northern Rio de Janeiro followed the predicted route of asteroid 2001
CA21 to look for a new path to reach Mars. The results, published in the journal Acta Astronautica, identify a course that would take
approximately 153 days for a round trip to the Red Planet and back. "

"The paper does not suggest that future missions must follow this
specific asteroid. Instead, it demonstrates a possible way to identify faster flight paths that traditional methods might miss. "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." "

I took a quick look at both articles, and still have no idea as to how
the faster trip is obtained, and what observing asteroids have to do
with it.

Up till now, we've used Hohmann transfer orbits, which are optimized to
reduce fuel consumption, which is considered the limiting factor.

We've long known that a faster trip can be done at the expense of more
fuel, and I don't see anything in these articles about the difference
in fuel consumption. So what is new?

I'm puzzled.

pt

--- PyGate Linux v1.5.14
* Origin: Dragon's Lair, PyGate NNTP<>Fido Gate (3:633/10)

On 5/3/26 11:46 AM, Stefan Ram wrote:

Cryptoengineer <petertrei@gmail.com> wrote or quoted:

I took a quick look at both articles, and still have no idea as to how
the faster trip is obtained, and what observing asteroids have to do
with it.

The article links probably are clickbait based on
"Round-Trip Mars Missions in the 2031 Window: Feasible and
Extreme Scenarios Derived from CA21-Anchored Trajectories"
(2025-10-24) by Marcelo de Oliveira Souza.

While that is surely a related precursor by the same author, the summary articles I linked to are based on:
" Using asteroid early orbital data for rapid mars missions "
in the Sept 2026(!) volume of Acta Astronautica.
Here's the doi:
https://doi.org/10.1016/j.actaastro.2026.04.018

--- PyGate Linux v1.5.14
* Origin: Dragon's Lair, PyGate NNTP<>Fido Gate (3:633/10)

On 5/3/26 11:12 AM, Cryptoengineer wrote:

On 5/3/2026 9:11 AM, Tony Nance wrote:

No joking: Get there in as little as 56 days, roundtrips as short as
153 days

https://phys.org/news/2026-04-interplanetary-shortcut-
mars.html#google_vignette

and

https://gizmodo.com/astronomer-finds-a-shortcut-to-mars-by-following-
an- asteroids-journey-through-space-2000752127

Some quotes:
" In a new study, Marcelo de Oliveira Souza of the State University of
Northern Rio de Janeiro followed the predicted route of asteroid 2001
CA21 to look for a new path to reach Mars. The results, published in
the journal Acta Astronautica, identify a course that would take
approximately 153 days for a round trip to the Red Planet and back. "

"The paper does not suggest that future missions must follow this
specific asteroid. Instead, it demonstrates a possible way to identify
faster flight paths that traditional methods might miss. "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." "

I took a quick look at both articles, and still have no idea as to how
the faster trip is obtained, and what observing asteroids have to do
with it.

Up till now, we've used Hohmann transfer orbits, which are optimized to reduce fuel consumption, which is considered the limiting factor.

We've long known that a faster trip can be done at the expense of more
fuel, and I don't see anything in these articles about the difference
in fuel consumption. So what is new?

I'm puzzled.

pt

I believe it's new geometry/trajectories, and (in the case of 2031) not
much different energy.

The source article is located at/via https://doi.org/10.1016/j.actaastro.2026.04.018

and includes such early paragraphs as:

"Using short-way Lambert-based trajectory construction constrained to
remain within of the CA21 orbital plane and high-fidelity JPL Horizons ephemerides, three Mars opposition windows (2027, 2029, and 2031) are analyzed. The 2031 opposition emerges as uniquely favorable under the CA21-plane constraint, yielding two outbound Earth Mars trajectories (33
and 56 days) and corresponding dynamically consistent return legs
forming complete round-trip architectures of approximately 153 and 226
days total duration."

"Sensitivity analysis demonstrates that these CA21-anchored solutions
remain geometrically stable under controlled boundary-state
perturbations, and Monte Carlo re-evaluation confirms numerical
robustness of the Lambert construction. While the asteroid itself is not
used as a physical waypoint, its early orbital plane serves as a
geometric template that highlights structured rapid-transfer corridors
within the 2031 opposition geometry."


"To evaluate whether such preliminary geometry can guide transfer
design, the study examines three Mars opposition windows, 2027, 2029,
and 2031, under a CA21-anchored plane constraint. A three-dimensional
Lambert solver [[3], [4], [5], [6], [7], [8]] is employed, with the transfer-plane normal constrained to remain within 5ø of the CA21 orbital-plane normal. Exact heliocentric state vectors obtained from
NASA's JPL Horizons system [1,2] are used to evaluate trajectory
feasibility and reconstruct daily ephemerides for dynamical consistency checks."

"The analysis shows that while the 2027 and 2029 windows exhibit high energetic barriers and weak geometric alignment, the 2031 opposition
provides symmetric outbound and inbound opportunities consistent with
the CA21 reference plane. Within that window, two short-way Earth Mars trajectories are identified: a 33-day rapid case and a 56-day feasible
case, each paired with dynamically coherent return legs to form complete Earth?Mars?Earth round-trip architectures."

"This study provides a focused investigation into whether an early
small-body orbital solution can serve as a geometric reference for
exploring rapid Earth?Mars transfers [[3], [4], [5]]. Using the initial
2015 JPL Horizons solution for 2001 CA21, the analysis demonstrates that
its early orbital plane?despite later refinements?can support a
constrained Lambert-based evaluation of short-duration opposition-class trajectories [[3], [4], [5]]. Within this framework, two complete Earth?Mars?Earth round-trip configurations are identified during the
2031 window: a high-energy 33ÿ+ÿ30 + 90 day mission (÷153 days total)
and a feasible 56ÿ+ÿ35ÿ+ÿ135 day mission (÷226 days total). Both are
shown to be dynamically coherent through full ephemeris reconstruction
using n-body JPL Horizons state vectors."


--- PyGate Linux v1.5.14
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Stefan Ram <ram@zedat.fu-berlin.de> wrote:

"Round-Trip Mars Missions in the 2031 Window: Feasible and
Extreme Scenarios Derived from CA21-Anchored Trajectories"
(2025-10-24) by Marcelo de Oliveira Souza.

So what I take from this: What might be new is the restriction
of travel to a plane. The paper says,

Not so sure about that... I think the idea is to _not_ restrict travel to
the plane of the ecliptic but to a plane intersecting the ecliptic.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

--- PyGate Linux v1.5.14
* Origin: Dragon's Lair, PyGate NNTP<>Fido Gate (3:633/10)

On 5/3/2026 12:00 PM, Stefan Ram wrote:

ram@zedat.fu-berlin.de (Stefan Ram) wrote or quoted:

The article links probably are clickbait based on
"Round-Trip Mars Missions in the 2031 Window: Feasible and
Extreme Scenarios Derived from CA21-Anchored Trajectories"
(2025-10-24) by Marcelo de Oliveira Souza.

So what I take from this: What might be new is the restriction
of travel to a plane. The paper says,

. . .
|This work establishes, for the first time, a complete and
|dynamically coherent framework for round-trip Earth?Mars?Earth
|missions within the 2031 opposition, derived from the
|CA21-anchored astrodynamics approach. Using precise
|Lambert-based modeling and JPL Horizons ephemerides, two
|closed trajectories were identified and validated: an extreme
|33+30+90-day configuration and a feasible 56+35+135-day
|configuration. Together, they demonstrate that sub-year
|round-trip missions between Earth and Mars are not only
|geometrically possible but also dynamically consistent when
|constrained to the orbital plane of asteroid 2001 CA21.
|
|The extreme configuration defines the upper physical limit of
|heliocentric transfer performance, requiring energy levels
|beyond current propulsion capability but remaining fully
|compatible with classical gravitational mechanics.
|It illustrates what could be achieved by future high-specific-
|impulse systems or staged orbit-to-orbit architectures.
. . .
What that paper says.

Yeah, it says 'if we had better rockets, we could get there
faster'.

Again, how is this news?

pt

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