Mars might have a shortcut.

A new study says a round trip to the Red Planet and back could take about 153 days by using early orbital data from an asteroid to map a more direct route through the solar system.

In the study, published in Acta Astronautica, 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.

A one-way trip to Mars usually takes between seven and 10 months on a fairly direct route between Earth and Mars.

Scientists planning interplanetary missions calculate routes based on the movements of planets through space. The distance between Earth and Mars changes constantly because of their orbits.

The planets are closest when they are on the same side of the Sun and farthest apart when they are on opposite sides of the Sun.

Every 26 months, Earth passes directly between the Sun and Mars. This alignment is known as the Mars opposition, and it is when spacecraft set a course for Mars.

Souza looked for a shortcut during the planet’s closest approach to Earth by following the early predicted path of a near-Earth asteroid that crossed the orbit of both Earth and Mars.

When astronomers first detect asteroids, they track their motion across the sky to model their orbits around the Sun. As more observations come in, those orbital paths become more refined.

That happened with asteroid 2001 CA21, but the study says its initial orbital path may still be useful.

The asteroid’s early orbital predictions describe a highly eccentric trajectory with a well-defined sub-ecliptic orbital plane, the plane that contains Earth’s orbit around the Sun.

Souza searched for a route to Mars that stayed within 5 degrees of the asteroid’s tilt so a spacecraft could take a more direct flight.

He then examined three possible launch windows to Mars during opposition in 2027, 2029 and 2031 to find the best conditions for a shorter trip.

The study found 2031 was the only year in which Earth-Mars geometry aligned favorably with the asteroid’s orbital plane.

During that 2031 launch window, the study identifies two possible round-trip Mars mission profiles with total durations of about 153 days and 226 days.

The research says early asteroid orbital predictions could be a tool for planning interplanetary routes and could cut hundreds of days from the itinerary.

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