Cosmic Space

Uranus and Enceladus top planetary scientists’ to-do list

Uranus has long been the butt of jokes, but the ice giant is finally getting its day in the sun, thanks to a recommendation in the National Academies’ newly released survey of potential interplanetary missions.

The decadal survey, drawn up by teams of scientists, serves as a roadmap for research in planetary science and astrobiology over the next 10 years. And the survey’s highest priority for multibillion-dollar flagship missions is to send an orbiter and a piggyback atmospheric probe to Uranus (preferably pronounced “urine-us,” not “your-anus”). Launch would come as early as 2031 or 2032, when the orbital mechanics are optimal for a multibillion-mile cruise.

In preparation for this decadal survey, a team of scientists led by NASA and the Jet Propulsion Laboratory drew up preliminary plans for a mission to Uranus or its ice-giant neighbor, Neptune.  Separately, Purdue University researchers developed a mission concept called OCEANUS (Observatory Capture Exploring the Atmospheric Nature of Uranus and Neptune) that included a Saturn flyby as well as a years-long study of Uranus.

The second flagship priority is a mission to Enceladus, an icy moon of Saturn that’s thought to harbor a subsurface ocean and potentially an exotic form of life.

Scientists at the Johns Hopkins University Applied Physics Laboratory have already started working out a concept for an innovative type of “orbilander” that would sample Enceladus’ plumes of water vapor from orbit, and then descend to the surface to sample and analyze the moon’s ice. The concept calls for a mission launch in 2038.

The two proposed flagship missions wouldn’t deliver their scientific payoff until the 2040s or the 2050s. Nevertheless, the scientists who wrote up the survey say the payoff would be well worth the investment.

Studying Uranus, its moons and its rings would provide an unprecedented opportunity to learn about a type of world that’s thought to be common in distant star systems.

“Uranus itself is one of the most intriguing bodies in the solar system: an extreme axial tilt; low internal energy; high-speed winds and active atmospheric dynamics; and complex magnetic field all present major puzzles,” the survey says. “It is unclear when and where Uranus formed, or if it swapped positions with Neptune during early solar system migration.”

The survey’s authors say that missions to either Uranus or Neptune would have equal scientific merit, but add that the technical readiness for a Uranus mission is higher.

Enceladus is in the spotlight because it’s a good contender — along with Mars and an icy moon of Jupiter called Europa — to provide evidence of life, most likely on the microbial scale. “This addresses one of the most fundamental questions in solar system science: is there life beyond Earth, and if not, why not?” the survey says.

NASA typically sticks close to the National Academies’ series of decadal surveys when it selects space missions for future funding. Europa, for example, was targeted for a flagship mission after it scored highly in the 2010 decadal survey. It’s likely that Uranus and Enceladus will get similar attention, although there are no guarantees.

“We look forward to reviewing the recommendations in detail,” Thomas Zurbuchen, NASA’s associate administrator for space science, said in a tweet.

Here are other priorities listed in the survey released today:

Planetary defense: The survey calls on NASA to support the development and launch of NEO Surveyor, a space probe that would scan our cosmic surroundings in mid-infrared wavelengths to look for potentially threatening near-Earth objects, or NEOs. It also supports a demonstration mission that would conduct a rapid-response NEO flyby as a rehearsal for dealing with cosmic threats.

Mars exploration: The survey supports the current campaign to bring samples back from Mars for study on Earth, but cautions that the costs and the scope of the campaign shouldn’t be allowed to undermine other interplanetary initiatives. A proposed mission designed to look for signs of extant life and modern-day habitability on the Red Planet, known as Mars Life Explorer, also gets a thumbs-up.

Moon exploration: NASA’s big-ticket exploration project, the Artemis program to send astronauts to the moon, is outside the scope of the decadal survey. However, the survey’s authors say the highest priority for medium-class robotic exploration of the moon would be the Endurance-A rover. Such a mission would collect a substantial mass of high-value samples across a wide swath of the lunar surface, and then deliver them to astronauts for return to Earth.

Other destinations: The report says NASA should consider other  concepts such as a Centaur Orbiter and Lander, which would study a class of icy worlds orbiting between Jupiter and Neptune; a mission that would bring back samples from Ceres, a dwarf planet with reserves of water; a comet surface sample return mission; a probe that would make multiple flybys past Enceladus; a plan for a Lunar Geophysical Network; and probes that would head for Saturn, Titan and Venus.

The survey released today focuses on planetary science and astrobiology, but a different survey sets priorities for astrophysics and astronomy. That survey, released last November, called for spending billions of dollars on next-generation telescopes on Earth and in space.

By Alan Boyle

Mastermind of Cosmic Log, contributor to GeekWire and Universe Today, author of "The Case for Pluto: How a Little Planet Made a Big Difference," past president of the Council for the Advancement of Science Writing.

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