Our galaxy may contain billions of habitable worlds that don’t host any life. Should we attempt to change that?

at the Goethe University Frankfurt, Germany, thinks we should. He believes in directed panspermia: deliberately seeding life throughout the cosmos. And to do that, he proposes we use a laser propulsion system that may not be technically out of reach.

is a project with ambitious aims to use such systems to send tiny, lightweight probes to Alpha Centauri. The goal is to take pictures of our nearest star, but these systems could also deliver much larger payloads into orbit around nearby stars, says Gros.

Potential targets include the planetary system around TRAPPIST-1, a red dwarf star just 40 light years away. Earlier this year, astronomers revealed it was home to seven rocky planets, three of which orbit within the star’s habitable zone.

Starshot’s proposed 20-year mission to our nearest star after the sun would rely on ultralight craft propelled up to 20 per cent of the speed of light by giant, Earth-based lasers pointed at a light sail – essentially a mirrored surface. While there are unprecedented challenges, particularly in laser design and the reflectivity of the light sail, the team remains confident of the mission’s feasibility.

“It is just a matter of the will to make it happen,” says at the Korea Astronomy and Space Science Institute. However, with no way to stop, Starshot’s single gram craft would zoom past its target star system just hours after arrival.

Genesis project

Could the laser propulsion instead deliver a heavier, slower moving payload with an onboard braking system into orbit? Gros says it could – and it should.

His interest in interstellar travel is not exploratory, or even scientific. He is focused on spreading life.

“These kind of projects are useless for humanity, but life is something valuable and should have the possibility to develop on other planets,” he says.

Gros feels emboldened in his quest by that planets orbiting the most common type of stars in our galaxy, red dwarfs like TRAPPIST-1, may have ancient, oxygen-rich atmospheres. Although these would make them habitable today, they could have prevented life forming initially due to the oxidation of prebiotic organic chemistry.

“Our galaxy may contain billions of sterile but habitable worlds,” says Gros.

Under his proposed Genesis project, Gros is looking at the possibility of launching into space autonomous toolkits for life: miniaturised versions of the gene laboratories envisaged by researchers here on Earth. These would grow genes and cells from chemical ingredients and disseminate them across habitable planets.

But how would these heavier payloads be slowed down upon arrival? Sails again have been suggested, but instead of acting as mirrors, they would be magnetic fields that stretch for kilometres and transfer the probe’s momentum to the interstellar particles hitting them. Once the lasers used for launch are no longer propelling them, they would use space dust to slow down.

Magnetic sail

Deep space can be near empty, perhaps containing just one atom per cubic centimetre, so sails with a large surface area would be needed to make this work. Gros says that with the latest high-temperature superconducting wires – those that can transfer energy with barely any loss at temperatures above absolute zero – possible to produce magnetised sails large enough to slow down a heavier craft.

Gros simulated interstellar particles hitting a magnetic sail and found four parameters determined a successful deceleration: the spacecraft mass, its velocity and therefore mission duration, the sail radius and the current flowing through the loop of superconducting wire within the main craft that would power the magnetic sails.

“A superconducting current could be created just once prior to launch and run for eternity,” Gros says. The technology could certainly operate long enough for a mission to a relatively nearby star system like TRAPPIST-1.

Gros estimates that a 1.5-tonne craft carrying the superconductor infrastructure for sails 50-kilometres wide could reach TRAPPIST-1 in 12,000 years if propelled by Breakthrough’s lasers.

, a Starshot adviser and physicist at the University of Hawaii, likes the paper, but worries that gaining support and funding for a mission that takes 12,000 years might be harder than actually building and launching one.

“This doesn’t necessarily mean we shouldn’t be doing this, but the timescales are so long that it’s hard to imagine human organisations with this attention span,” Kuhn says.

Hoang instead worries whether the superconducting ring itself could survive collisions with interstellar dust, though he agrees with Gros that the Starshot system could technically launch such a mission. “The project did not discuss the potential implication of a long-term mission for panspermia,” he says. “I think that it would be interesting to use the proposed system to spread some form of life to the interstellar space.”

THE dark outer reaches of our solar system could be hiding a new planet – the ninth or tenth, depending on who’s counting. The as-yet-unconfirmed world, thought to be around the mass of Mars, would explain the wonky orbits of a group of icy objects in a region known as the Kuiper belt.

This region starts beyond Neptune and ends at a distance 55 times further from the sun than Earth is, or 55 AU. We have spotted an increasing number of its residents, with the discovery of numerous Pluto-sized objects leading to the former ninth planet’s downgraded status.

But could something larger lie out past Neptune? and at the University of Arizona believe so. They have uncovered signs of weird warps in the orbits of distant Kuiper belt objects.

Earth and the other familiar planets all orbit the sun in roughly the same plane. But the smaller Kuiper belt objects are far enough from the gravitational influence of the giant planets that they can orbit the sun at angles to this plane, nudged by their own gravitational interactions and past collisions.

It is possible to predict this angle, known as the inclination, for any object we observe. If those calculations don’t match the real path of the objects, it hints there is something lurking out of sight, tugging on the bodies we can see.

Last year, Mike Brown and Konstantin Batygin at the California Institute of Technology used this idea to predict the existence of a ninth planet, thought to be 10 times the mass of Earth, orbiting around 700 AU from the sun.

“It’s not what we expect if the only planets in our solar system are those we already know”

Now Volk and Malhotra have looked closer to home. In a study due to be published in The Astronomical Journal, they report that beyond 50 AU, the inclination of objects in the Kuiper belt differed from predictions by 8 degrees, on average.

“It’s not what we expect if the only planets in our solar system are those we know of,” says Volk. That means throwing a new planet into the mix – Planet Ten, assuming Planet Nine exists.

To cause this orbital warping, it must have a similar mass to Mars. It may have arrived there after being ejected in an ancient game of gravitational billiards. “If it’s the size of Mars, that is a pretty big object, which would suggest it would be most likely scattered out there by planetary movements further in,” says Volk.

An out there idea

“This fits really nicely with how we expect planets formed in the early solar system,” says Michele Bannister of Queen’s University Belfast. Various models show a family of small planets thrown outwards early in their development, probably by the migration of Neptune.

“It’s an interesting idea. One that deserves attention,” says Batygin. But given its mass and distance, it should be bright enough to have been seen by now, he says, although it could be obscured by the bright galactic centre.

Others are wary of introducing new worlds to the solar system. “I am dubious that a planet so close and so bright would have remained unnoticed,” says at the Côte d’Azur Observatory in Nice, France, who suggests that Planet Nine could account for at least some of the deviation.

Volk and Malhotra say finding more Kuiper belt objects will firm up their data. More information could come from the , which is hunting and tracking thousands of objects. Bannister, who works on the survey, has used its data to search for Planet Nine, though the results were inconclusive ().

Just how many new planets are out there remains to be seen, but Volk is confident in her finding. “It would have to be quite a fluke for this to not be a real effect,” she says. “We think there is a real signal there and this implies an additional planet.”

This article appeared in print under the headline “A new planet just round the corner?”

Keeping an atmosphere