NASA has set four different Discovery Program investigations in an elimination match; two to Venus, one to Jupiter's Io, and another to Neptune's moon, Triton. Only two will make it to space, and the final decision comes in 2021.
NASA's Discovery Program
NASA's Discovery Program is calling for scientists and engineers to build teams capable of designing the next generation of planetary science missions, to deepen our knowledge of the solar system, and — of course — our place in it.
"These selected missions have the potential to transform our understanding of some of the solar system's most active and complex worlds," said Associate Administrator of NASA's Science Mission Directorate Thomas Zurbuchen. "Exploring any one of these celestial bodies will help unlock the secrets of how it, and others like it, came to be in the cosmos."
Every one of the four nine-month studies gets $3 million to workshop their concepts, each concluding with a "Concept Study Report." Once evaluated, NASA will continue development with two of the four missions, leaving the others out of the game.
Selected through a competitive peer-review process of value and feasibility, the candidate proposals are as follows:
Trident, to Neptune's icy moon Triton
Project Trident would if selected explore Neptune's moon, Triton, to study the ways that worlds far away from the Sun might one day be habitable. NASA's Voyager 2 mission revealed that Triton possesses active resurfacing — high turnover of its literal surface — which is why it's the second-youngest surface in the solar system. It might also have erupting plumes, and an atmosphere.
The principal investigator is Louise Prockter, of the Lunar and Planetary Institute/Universities Space Research Association. If selected, NASA's Jet Propulsion Laboratory would manage the mission.
VERITAS, for Venus
VERITAS, which is an acronym for Venus Emissivity, Radio Science, InSAR, Topography, and Spectroscopy, will if selected analyze the planet's geologic history, and work to determine why it is that Venus turned out so differently than Earth. In orbit of Earth's sister-planet, VERITAS would use a synthetic aperture radar to chart surface elevations that span almost the entire planet. It will create 3D reconstructions of topography, eventually learning whether processes on Earth — like plate tectonics and volcanism — are still happening on Venus. VERITAS would also scan infrared emissions that come from the surface to learn the geology of Venus, which is still a big unknown to the scientific community.
The principal investigator is Suzanne Smrekar, of NASA's Jet Propulsion Laboratory, so naturally JPL would manage the mission.
Another attractive acronym: Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging Plus. DAVINCI+ would study the atmosphere of Venus, to learn how it formed and evolved, and also attempt to learn whether the hot planet ever had an ocean. This mission would thrust into the harsh environment of Venus' inhospitable atmosphere to analyze its composition, all the way down to the ground.
The instruments onboard would be contained within a custom-made descent sphere, to protect them from the damaging environment of the broiling planet. The "+" in DAVINCI+ stands for imaging carried out by cameras, both on the orbiter, and the descent sphere.
The last time a U.S.-led mission to Venus happened was in 1978, so a return mission with modern technology is sorely needed.
The principal investigator is James Garvin, of NASA's Goddard Space Flight Center. Goddard would manage the mission.
Io volcano observer (IVO)
IVO would fly to Jupiter's moon Io, to study the way tidal forces mold and shape planetary bodies. Io is stretched and squeezed by the differential pull of Jupiter's immense gravity, which heats the moon into the most volcanically-active body in the solar system.
There's not much one can say about Io's (let's say) unique characteristics, like whether a magma ocean exists in its interior, or not. Via close flybys, IVO would help scientists study how magma is generated — and eventually erupts — on the active planet.
This mission might transform our understanding of how rocky, terrestrial planets form and evolve, and it could also help us learn how icy ocean worlds in our solar system form, in addition to other icy worlds beyond our solar system.
The principal investigator is Alfred McEwan, of the University of Arizona. The Johns Hopkins University Applied Physics Laboratory would manage this mission.
It's hard to choose which one will win, but from the mission statements alone, it seems like a fair bet that IVO won't lose, purely on the observation that our findings on Io could also expand our knowledge of other, very-different-looking planetary bodies. It feels like a scientific two-for-one.
May the best missions win.