Seven Things You Need To Know About NASA’s New $4.9 Billion Mission To Enceladus, A Tiny Moon Of Saturn
NASA is going to Enceladus! Last month the National Academy of Sciences finally published its Decadal Survey for Planetary Science and Astrobiology—widely regarded as a “to do” list for NASA—and star of the show was the recommendation for NASA to develop the Enceladus Orbilander mission to explore Saturn’s sixth largest moon.
Enceladus has a warm salty ocean below its icy surface. It also has plumes or geysers that spew that liquid into space. That means unparalleled access to an extraterrestrial ocean, which is why some planetary scientists and astrobiologists rank it as the most exciting object in the Solar System. However, Orbilander is not going to get to Enceladus anytime soon.
Here are seven things you need to know about the jaw-dropping plans for Orbilander to both orbit and land on Enceladus:
1. Orbilander will land and take photos
Orbilander will orbit Enceladus, essentially to sample its plumes—as ice particles in space—twice per day for 200 days. Then it will land. Enceladus has about a hundredth of the gravity on Earth, so landing should be relatively easy compared to Mars. It will then stay on the surface for a couple of years at least, occasionally changing position, to take (likely much larger) samples of that plume material that have fallen back.
It will also have cameras on board to send back photos from orbit and of the surface, as well as a seismometer to catch any “icequakes.” At the end of the mission Orbilander will remain on the Enceladean surface.
2. It won’t arrive until 2050—and that’s perfect
The Orbilander concept suggests a launch in October 2038 (with a backup in November 2039) to arrive in 2050. That’s a long time, with Orbilander not scheduled to be started on by NASA until 2029 at the earliest. Sure, 2050—at least—is a very long time to wait for the first science results from a NASA mission.
That’s exploring the outer solar system for you.
Yet there’s a good scientific argument to wait until then anyway. Beginning the development of Orbilander late in the 2020s means arriving at Enceladus in the early 2050s when its south pole will be coming into southern summer. It means more of the moon will be illuminated as the mission goes on.
3. It might launch on a SpaceX Starship spaceship
To reach Saturn in seven years—which would be followed by a four-year “moon tour” to “pump down” its speed so it can get into orbit of its target—the Enceladus Orbilander requires a super-heavy lift launch vehicle. That probably means NASA’s Space launch System (SLS), though it could also mean the SpaceX Starship vehicle. Both are still in development.
However, it could launch on a heavy lift vehicle—like the SpaceX Falcon Heavy—if it also included a solar-electric propulsion stage and/or a Jupiter gravity assist. Venus and Earth-gravity assists would also be possible. But for either we’re then talking nine or 10 years just to reach Saturn.
4. It will search for life
Enceladus is an ice-rock world with active plumes of gas and particles that originate from its subsurface ocean. So Orbilander will be able to study material in its plumes as if directly sampling its subsurface ocean for signs of habitability.
The main science objectives of Orbilander are:
- to search for evidence of life.
- to obtain geochemical and geophysical context for life detection experiments.
5. Enceladus is tiny
The main issues with the Orbilander mission concept is that Enceladus is so very small. It’s just 311 miles/500 kilometers in diameter—the same distance from London and Edinburgh—so physically getting out of Saturn orbit and into orbit around Enceladus won’t be easy.
Cue a four-year tour of Saturn’s moons to slow it down and get it onto the right trajectory to intercept Enceladus.
6. It will cost $4.9 billion … or $900 million
If NASA just can’t afford to begin development of the $4.9 billion Orbilander mission it does have a Plan B from the committee. Also on the roster is the Enceladus Multiple Flyby (EMF) concept, a more affordable “New Frontiers” mission costing less than $900 million. EMP is a flyby mission that would have a spacecraft collect plume samples while traveling at 4 km/s—not ideal—and it would gather 100 times less material than Orbilander. EMF would also lack life-detection capability and be unable to provide any geological or geophysical context.
If Orbilander gets started by 2030, on target, then EMF is history, states the Decadal Survey report. “When we generate a Decadal Survey, we do not know what the budget will be over that 10 years, and there are many pulls on the funding,” said Amy Simon, senior scientist for Planetary Atmospheres Research in the Solar System Exploration Division at the NASA Goddard Space Flight Center, and a member of the committee that prepared the report. “While we’d like two new Flagships to be started in the decade, that may or may not be affordable, so allowing Enceladus to remain in New Frontiers allows extra flexibility.”
7. Enceladus Orbilander isn’t guaranteed
Despite beating rival concept missions—specifically the Europa Lander, the Mercury Lander, the Neptune-Triton Odyssey Flagship and the Venus Flagship—Orbilander is only the second- highest priority new flagship mission after the Uranus Orbiter and Lander.
Given that NASA is already committed to the Mars Sample Return mission to go get the rocks now being collected by its Perseverance rover—and that the Uranus Orbiter and Lander was ranked third in the 2010 Decadal Survey and never got built—the chances of Orbilander becoming a reality are still in the balance.
“Orbilander provides an outstanding opportunity to explore the astrobiological conditions of ocean worlds and will revolutionize our understanding of these worlds,” says the Decadal Survey report.
That’s got to be worth the wait.
Wishing you wide eyes and clear skies.