Would you like NASA to fly a drone across Saturn’s biggest moon, or to send a probe to gather samples from a duck-shaped comet?
From a dozen offers to the agency’s New Frontiers competition — not unlike an interplanetary “Shark Tank” for a forthcoming robotic mission — NASA declared these two finalists on Wednesday.
“It’s one of the most difficult programs to be selected for,” said James L. Green, director of the planetary science division at NASA. “We fly only about two of these kinds of missions per decade.”
In the first proposed mission, Comet Astrobiology Exploration Sample Return, or Caesar, a spacecraft would go to Comet 67P/Churyumov-Gerasimenko, already explored by the European Space Agency’s Rosetta mission, and carry back a little chunk to Earth for closer study.
In the second mission, named Dragonfly, a robotic drone would be sent to Titan, Saturn’s biggest moon, which has seas of hydrocarbons. The drone would be capable to fly from one location to another and to perform detailed explorations of different terrains.
“These are extremely exciting missions,” Dr. Green said.
Each team now will get $4 million and about one year to flesh out its idea. NASA will decide in mid-2019 which one of the two to build. The selected mission is to launch by the end of 2025.
NASA flies two kinds of science missions. In the first kind, which includes the Mars Curiosity rover and a arriving spacecraft that will analyze Jupiter’s moon Europa, the agency decides where it needs to go and then builds and operates the mission itself.
But for the second type, NASA tries to sell suggestions from inside and outside the space agency. Previous New Frontiers missions include New Horizons, which zipped past Pluto two years ago; Juno, presently looping around Jupiter; and Osiris-Rex, presently en route to an asteroid.
For this round of New Frontiers, NASA will spend up to $850 million for the spacecraft, equipments and mission operations. Add in the cost of the rocket to get the spacecraft off the ground, and the total price tag will be about $1 billion.
Steven W. Squyres, a professor of physical sciences at Cornell University who leads the Caesar proposal, said his team chose Comet 67P because of the wealth of data gathered by the Rosetta mission, which flew alongside the comet from 2014 to 2016.
“We are capable to design our mission, design our spacecraft specifically for the conditions that we know to exist there,” Dr. Squyres said. “And what that does is just dramatically progress the chances for success for a very difficult activity, which is grabbing a piece of a comet.”
Comets are trusted to contain primitive ingredients from the early solar system that went into the building of the planets.
Caesar would scoop up at least 100 grams from the comet, separating the volatiles — constituents that could evaporate — from the more solid elements. The spacecraft would then head back to Earth and drop off the sample in a capsule.
“The sample will come back on Earth on the 20th of November, 2038,” Dr. Squyres said. “So mark your calendars, and once it’s been delivered to laboratories worldwide, I think it’s going to produce groundbreaking science for decades to arrive.”
The Dragonfly mission would follow up on experience made by the Cassini-Huygens mission that concluded in September. The Huygens probe, built by the European Space Agency, landed on Titan in 2005. The Cassini orbiter made many flybys of Titan during its 13 years in orbit around Saturn.
Powered by a chunk of plutonium, Dragonfly would take benefit of recent technological advances in flying drones. The craft would spend most of its time making analysis on the ground, but it would be able to fly tens or hundreds of kilometers through Titan’s thick atmosphere to study other geologic terrains, said Elizabeth Turtle, a planetary scientist at the Johns Hopkins University Applied Physics Laboratory who is the principal investigator for Dragonfly.
“In this way, we can check how far prebiotic chemistry has progressed in an environment that we know has the ingredients for life — for water-based life or potentially even hydrocarbon-based life,” Dr. Turtle said.
NASA also decided to finance further technological development of two other proposals: Enceladus Life Signatures and Habitability, or Elsah, which proposes to study icy plumes arising from Enceladus, a little moon of Saturn; and Venus In situ Composition Investigations, which searches to put two landers on the planet’s surface.
Other proposals that NASA did not seek include MoonRise, which would have brought back soil and rock from the moon’s South Pole-Aitken Basin, the scar of a cataclysmic impact more than four billion years ago; and Sprite, a probe that would have parachuted onto Saturn.