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Four Shortlisted NASA Missions Would Explore the Nastiest Places in the Solar System

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NASA’s Galileo spacecraft caught Jupiter’s moon Io experiencing a volcanic eruption on June 28, 1997.
Image: NASA/JPL/DLR

As part of its ongoing Discovery Program, NASA has selected four possible missions that would involve some of the most hostile and enigmatic places in the solar system.

Established in 1992, NASA’s Discovery Program “gives scientists a chance to dig deep into their imaginations and find new ways to unlock the mysteries of our solar system,” according to the program website. Projects previously chosen under the Discovery Program include the Kepler space telescope, the Lunar Reconnaissance Orbiter, and the InSight lander, which is currently on Mars. Upcoming missions include ones to explore Jupiter’s trojan asteroids, the 210-kilometer-wide (130 miles) 16 Psyche asteroid, and the Martian moon Phobos.

So yeah, this program has a pretty decent track record—and as the newly announced batch of possible missions indicates, this is a happy trend that’s set to continue.

Due to the way the Discovery Program works, proposed missions can’t step on the toes of ongoing or pre-approved projects. Accordingly, these four new concepts, all of which have yet to receive final approval, involve missions to previously neglected yet highly valuable scientific targets. In this case, the destinations would include Venus, Jupiter’s moon Io, and Neptune’s moon Triton.

The planners of these four shortlisted missions will now embark upon nine-month studies to further flesh out their concepts, and they’ve all been given $3 million in additional funding to make it happen. All candidates will have to further develop and refine their concepts and submit a formal Concept Study Report to the Discovery Program.

Let’s take a look at the four candidates in more detail.

Conceptual image of DAVINCI+ during its descent toward the surface of Venus.
Image: NASA/GSFC

First, there’s DAVINCI+, which stands for Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging Plus. Goddard Space Flight Center in Greenbelt, Maryland is the group behind this project, the primary purpose of which is to analyze Venus’s noxious, roiling atmosphere. Indeed, many lingering questions remain about this pressure cooker of a planet, such as how it formed and evolved and whether or not it once hosted liquid water at the surface.

During this brief mission, the spherical DAVINCI+ probe will use a parachute to slowly descend toward the surface, during which time it will take various measurements. In particular, the probe will try to sniff out traces of noble gases, such as xenon, which could reveal insights into Venus’s volcanic and hydrological past. The probe will also map the surface and detect different types of rock.

The instruments on DAVINCI+ will be protected from the planet’s tremendous heat and pressure, including a camera (which accounts for the + sign in the project name, a recent addition) that will snap pics during the hour-long descent. As to how long the probe will last once it’s on the surface, that’s anyone’s guess.

The Io Volcano Observer (IVO) would explore another hostile target, Jupiter’s moon Io. This object is super volcanic, the result of tremendous gravitational forces imposed by its enormous, gaseous host. Io has the most dynamic surface of any object in the solar system, making it an excellent target for scientific exploration. Institutions involved in this bid include the University of Arizona in Tucson and the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland.

IVO would perform around 10 close flybys of Io during the five-year mission, which could be extended by an additional three years depending on how things go. The probe would reveal new insights into tidal heating and how heat builds up in the core and then spreads to the surface. These findings would help scientists better understand similar processes seen elsewhere, such as on Saturn’s moon Enceladus, which features a warm subsurface ocean.

Neptune’s moon Triton, as photographed by Voyager 2 in 1989.
Image: NASA/JPL/USGS

The Trident mission would see a spacecraft zoom past Triton, a poorly understood moon around Neptune. This proposed mission from the Lunar and Planetary Institute in Houston, with help from NASA’s Jet Propulsion Laboratory in Pasadena, California, would explore the potential for habitability at the extreme edges of the solar system.

Observations from NASA’s Voyager 2 probe revealed an icy yet highly active surface on Triton. And in fact, this moon features the youngest surface of any terrestrial body in the solar system, second only to Io. Triton might actually have its own atmosphere, which would make it only the second moon in our solar system known to host an atmosphere, the other being Saturn’s Titan. The moon might also be erupting material into space via cryovolcanoes (yes, literally ice volcanoes), and its ionosphere is thought to churn out complex organics that precipitate like snow. Excitingly, Triton could also feature a subsurface ocean.

The Trident mission would involve a single flyby, so it’d be a one-and-done deal, similar to the New Horizons mission to Pluto. Though brief, Trident would pass exceptionally close to the moon (within 500 kilometers), during which time it would map the surface, measure its ionosphere, and hunt for traces of a hidden ocean. As an added bonus, Trident would swing by Jupiter on its way to the Neptune system.

Conceptual image of VERITAS in orbit around Venus.
Image: NASA/JPL-Caltech

Finally there’s the VERITAS mission, which stands for Venus Emissivity, Radio Science, InSAR, Topography, and Spectroscopy. This low-cost, two-year mission would see a satellite stationed in orbit around Venus, where it would perform a detailed analysis of the planet’s surface. The primary purpose of this mission, led by NASA’s JPL, is to understand the differences and similarities compared to Earth. Essentially, why did Venus deteriorate into our evil twin?

Equipped with an array of sensors, VERITAS would create a 3D topographical map of Venus, hunt for signs of craters, tectonic activity, volcanism, and previous water, take the planet’s temperature, study its gravitational field, and perform a detailed geological survey.

The VERITAS mission could be seen as a rival the DAVINCI+ project. Its planners have designed the mission such that the satellite could deploy a nanosat probe into the atmosphere, where, with its mass spectrometer, it would hunt for noble gases.

It seems unlikely, therefore, that NASA would choose both the VERITAS and DAVINCI+ missions, but we’ll have to wait and see. Sadly, only one or two of these missions will get greenlit as an official NASA mission, a decision we can expect in 2021.

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