Next Great Interplanetary Mission

NASA Is Selecting Its Next Great Interplanetary Mission

The next great NASA spacecraft could go to Jupiter's volcano moon Io, or Saturn's ocean moon Enceladus, or perhaps to sample one of the most mysterious regions of our own moon.

Michael Stillwell

By Jay Bennett

NASA has received 12 mission proposals for their New Frontiers program, which will select a spacecraft to send to a new target in the solar system with a planned launch in the mid-2020s. Of the 12 proposals, one or more will be selected for Phase A studies in November, and one mission will be chosen in early 2019 to proceed with development with a budget around $1 billion. Launch is expected sometime around 2024.

NASA does not release information about the specific missions proposals, as they are considered proprietary information. However, in a talk given last night about the Grand Finale of the Cassini mission at Saturn, Project Scientist Linda Spilker mentioned that three of the proposals are for spacecraft to send back to the Saturn system. One probe would dive into the atmosphere of Saturn to sample the gas and determine its composition, one would return to the moon Titan to orbit and possibly land on the mysterious world of hydrocarbon lakes, and a third would return to Enceladus to sample and analyze the water ice that shoots out into space from the moon's geysers to search for things like amino acids—possible indicators of life.


Saturn's sixth-largest moon Enceladus, with a subsurface ocean and geysers that spew water ice out into space.
NASA/JPL-Caltech/Space Science Institute

Although NASA does not reveal specifics of any mission proposal, the agency does have a list of "mission themes" that the proposals should focus on. This list suggests a mission to Jupiter's moon Io to study the volcanism there might be one of the proposals, as well as a mission to land on Venus. However, this is simply speculation from the list of "mission themes," which are as follows:

• Comet Surface Sample Return
• Lunar South Pole-Aitken Basin Sample Return
• Ocean Worlds (Titan and/or Enceladus)
• Saturn Probe
• Trojan Tour and Rendezvous
• Venus In Situ Explorer

One of the most intriguing "mission themes" is a lander to sample the South Pole-Aitken (SPA) basin of our own moon. This massive impact crater on the far side of the moon is one of the largest in the entire solar system, stretching about 1,600 miles in diameter. It is also thought to be the oldest impact crater on the moon, at least 3.9 billion years old and possibly older.


Concept of a lunar lander to sample the South Pole–Aitken basin.
NASA

A sample from the SPA basin has never been obtained, and many planetary scientists are extremely eager to get their hands on some of this material because astrobiologists believe that life likely formed on Earth at the same time the SPA crater was created. Craters on Earth that are as old as the SPA basin have all been eroded away or buried under rock and water, but a sample from this lunar crater could act as a substitute for a terrestrial one. Analyzing the composition of the SPA could potentially answer one of planetary science's biggest questions—did life spark from material on Earth that stewed in the right conditions for long enough, or was it brought here by an impacting asteroid?

NASA's New Frontiers program has previously launched three missions. New Horizons was the first, launched in January 2006, and it captured the world's attention when it made the first close flyby of Pluto in July 2015. Juno was next, and it arrived at Jupiter in July 2016 where it is currently studying the composition and structure of the largest planet in our solar system. OSIRIS-REx—the Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer—was launched in September 2016, and the craft will arrive at asteroid 101955 Bennu in 2018, where it will orbit until March 2021 and send a sample back to Earth that should arrive in 2023.


Enhanced-color image of Pluto taken by the New Horizons spacecraft on July 14, 2015.
NASA/JHUAPL/SwRI

The next launch of an exciting interplanetary spacecraft from NASA will be the Europa Clipper, designed to visit Jupiter's moon Europa, possibly land, and study the icy moon for signs of life. Europa Clipper is slated to launch around 2022, and the craft will be operated jointly by Johns Hopkins University's Applied Physics Laboratory (APL) and the Jet Propulsion Laboratory (JPL).

Spilker also mentioned talk within NASA about a mission like Cassini to Uranus or Neptune, but this would be a much larger and more expensive mission than the New Frontiers program provides for. Given the great distances to the two outer planets, it will be some time before the ice giants get their first orbiters even if talks about such missions have begun.

The solar system is full of more wonders than anyone could have guessed 10 years ago, with liquid water possible as far out as Pluto, geologic activity on practically every large object, and microbial life potentially as close as the Jupiter system, or even Mars. Here's to many more spacecraft, and many more discoveries that transform our understanding of the small celestial neighborhood we float in.