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We need to check out this space rock from the edge of the solar system — before it’s too late

We shouldn’t miss Sedna when it comes around, because if we do, it won't be back in over a hundred lifetime. 

By Elizabeth Rayne
Liz Planet Sedna GETTY

Pluto has several reasons to still be bitter about its demotion from planet planet to dwarf planet, and a mysterious object known as Sedna is one of them.

Sedna is an extremely distant trans-Neptunian object — possibly a dwarf planet — and one of the space rocks that made a case for Pluto being reclassified. It is also on its way towards its closest approach to the Sun on its 11,390-year-long orbit. While there are no official missions to Sedna yet, but scientists are vying for one. The ideal launch window will be in either 2029 or 2034 (especially 2029) before it’s going to be gone for over a hundred lifetimes again.

We shouldn’t miss Sedna, because besides having an unusually ginormous orbit for a dwarf planet, it could reveal mysteries that still lurk at the furthest reaches of the solar system. Researcher Vladislav Zubko and his team from the Space Research Institute at the Russian Academy of Sciences want to see this mission happen by 2029. They recently presented a study, in which they figured out possible trajectories to Sedna, at the Global Space Exploration Conference.

“In order to drastically reduce the increment of the spacecraft velocity at the stage of its acceleration near the Earth, necessary for the flight to Sedna, flight trajectories with flybys of Venus and Jupiter were considered,” study coauthor Alexander Sukhanov told SYFY WIRE. “Gravitational assists were used in most of the trajectories analyzed.”

Like the Voyagers and NASA’s recently launched Lucy mission that will fly back over here to take advantage of Earth’s gravity so it can be hurled to the Trojan asteroids, any mission to Sedna will have to depend on a gravity assist from planets such as Venus, Earth, or Jupiter if it’s going to get close enough for a flyby. An assist can reduce the velocity a spacecraft would need to accelerate to near Earth. That would lower how much fuel it burns and end up needing a lighter and less expensive launch vehicle that will bring down overall costs of the potential mission.

The most efficient gravity assist method is the VEEGA (Venus+Earth+Earth Gravity Assists) maneuver, which uses Earth and Venus flybys (with a repeat flyby of Earth) that hurls the spacecraft towards Jupiter without any additional fuel for launch. Something like this can also send it from Jupiter to Sedna faster by turning up its velocity and keeping fuel consumption down. From all possible trajectories analyzed in their study, the researchers chose those that would result in the hypothetical spacecraft needing the least fuel while zooming the fastest.

We should be that eager to see a Sedna mission. Despite its dethroning Pluto, the objects have something in common. Both are covered in reddish organic substances called tholins.

“Tholins, traces of water ice, pyroxene, and nitrogen may present on Sedna,” Zubko said. “Because of its great distance from the Sun, there may be formations of volatile substances on the surface of Sedna that have not evaporated due to the low temperature on the surface.”

Sedna is too far for telescopes on Earth to make detailed enough observations of what is actually lurking on the surface, and even New Horizons was not on the same trajectory to catch a glimpse of it. The orbit of Sedna reaches so far out that there might even be material from the Oort cloud that came along for the ride. It is possible that trace amounts of substances that may have not been part of the object’s formation, but picked up from the Oort cloud, could be on the surface. Primordial material like this may tell us more about the birth of the solar system.

“There might be impact craters on Sedna, the origin of which could be meteorites in the Oort cloud,” coauthor Andrey Belyaev said. “Since its orbit is mostly beyond the heliopause, its surface and atmosphere (if it has one) may have interacted with interstellar gas.”

Only Voyager 1 and 2 have ever gone beyond the heliopause, the outer limit of the heliosphere and basically the edge of the solar system. Beyond this point is the interstellar medium. Solar wind can just barely make it to the heliopause, and is weak from the journey. Whether Sedna is pristine is unknown, and so is its age, but preliminary research has already shown there are organics. It might also be hiding some really bizarre chemicals on its surface that might change what we think of how the solar system came into being. Even astronomers can only imagine.

What Zubko really wanted to prove with this study was that a Sedna mission would be viable even though this object seems almost out of reach. He and his colleagues were able to show that a spacecraft en route to Sedna would be capable of flying at a high velocity with the right gravity assists, even though getting through to the object’s orbit might still be tricky. He and coauthor Konstantin Fedyaev are still optimistic that a mission could become a reality.

“Even a simple passage of such a remote celestial body is already a new important step for humanity in the flight towards the interstellar space,” they said. “We will be able to better understand the evolution of the solar system and what awaits us in the future.”