LAUREL, Md. — Before NASA had confirmation that the New Horizons probe had completed its historic Pluto flyby July 14, the mission’s principal investigator Alan Stern admitted he is already contemplating a follow-on mission: A Charon lander that could study the surface Pluto’s largest moon while remotely observing the dwarf planet as an orbiter would.
“I’ve been thinking about the next thing to do, and in my own mind, I think that a lander is smarter. But the lander that I’d like to fly is actually a lander to Charon,” Stern said in a brief interview July 14, about an hour after the Pluto flyby. “We land on the Pluto-facing hemisphere of Charon, we have an orbiter that’s looking at Pluto every day from the surface, and we can look at all the small satellites as they move through the sky.”
The standard NASA operating model for robotic planetary science is, in order: fly by, orbit, land, rove, collect samples. Stern’s concept, which he dubbed a “hyper orbiter,” would combine orbiting and landing. However, the mission has hardly made it out of Stern’s own mind, let alone to a drawing board.
“I’ve just been thinking about it myself, to be honest,” Stern said when asked if he had shared the idea with other space scientists.
Even if the planetary science community starts laying the groundwork now, the earliest possible date for Pluto encore is some time between the early 2020s and the early 2030s: The range for which the community’s next decadal survey will prescribe top-priority missions for NASA’s Planetary Science Division.
Decadal surveys are 10-year roadmaps drafted by the science community under the auspices of the National Research Council. These documents run to the hundreds of pages and provide NASA with a compass for which missions to fund, and in which order. The last, published in 2011, was 400-pages long and set planetary science priorities through 2022.
In the most recent planetary science decadal, Pluto was mentioned mostly in connection with New Horizons. The rest of the sprawling Kuiper belt, a ring of bodies including potentially Pluto-like ones, appears in connection with only one possible future mission: a Neptune orbiter concept.
Astronomers had long suspected the Kuiper belt existed, but hard evidence came only in the early 1990s. Scientific interest in the Pluto system and the multitude of tiny worlds beyond spiked, but it still took nearly a decade — and false starts on five Pluto mission concepts — before New Horizons managed to run the scientific and political gamuts required to get funded.
Key to that victory was the 2003 planetary science decadal survey, in which scientists anointed the Pluto system and worlds beyond a top-priority destination. Congress relies heavily, although not exclusively, on decadal priorities when writing annual U.S. spending bills.
The first obstacle for a second mission to Pluto — no longer among the solar system’s unexplored corners — is getting that decadal priority back. That would require the entire planetary science community coming to an accord that the dwarf planet and its moons, one of which may even be geologically active, deserve a fresh injection of scarce NASA science dollars.
So far, only a tiny fraction of the data New Horizons collected about Pluto during the July 14 flyby has made it back to Earth, making it too early to say whether the mission made discoveries that will spur scientists to again push Pluto to the top of NASA’s to-do list.
But early results, including the abundance of nitrogen on the dwarf-planet, left the head of NASA’s $1.4-billion-a-year Planetary Science Division with the impression that New Horizons could again ignite decadal fervor over Pluto.
“I think Pluto is indeed an object we’re going to need to know more about,” Jim Green, NASA’s director of planetary science said in a July 14 interview at the Johns Hopkins University’s Applied Physics Laboratory here. “I think the excitement is there, the details, in terms of the science will come out … and they’re going to be pushing for what might be the next steps, you bet.”
The early bellwethers for community push are the mission-concept studies NASA funds early on in the decadal process. This study money helps scientists sound out the technical, budgetary and political feasibility of gathering the community’s most sought-after data sets. The agency funded 26 such studies ahead of the 2011 planetary decadal.
NASA will reach out to the National Research Council to begin the next planetary decadal survey process in 2018 or 2019, with an eye toward publishing a final survey around 2022, Green said.