“The Phase A analysis demonstrated that, frankly, the single lander breaks entry, descent, and landing heritage. Both are now scheduled for launch in 2028. The single sample retrieval lander mission would be split into two landers, one carrying a European “fetch” rover to pick up the samples and the other the Mars Ascent Vehicle rocket that will launch the samples into orbit. However, in March, NASA announced a change in the structure of the MSR campaign. The lander and Earth return orbiter missions would launch in 2026, bringing the samples back in 2031. The previous plan called for three missions: the Perseverance rover to cache the samples, a sample retrieval lander to pick up the samples and launch them into Mars orbit, and an Earth return orbiter that would pick up the samples and return them to Earth. It’s unclear that cost reflects changes in the MSR effort. NASA had not disclosed a formal cost estimate for the effort, and that price tag is more than either the Uranus or Enceladus missions endorsed by the decadal. The report provided a noteworthy data point about MSR: it estimates the cost of completing the effort of retrieving the samples and bringing them back to Earth at $5.3 billion. “Mars sample return should be completed as soon as practically possible with no changes in its current design,” said Phil Christensen of Arizona State University, the other co-chair of the decadal steering committee, at the rollout event. The decadal survey did endorse the MSR effort, calling it the “highest scientific priority” of NASA’s planetary science program. While the decadal survey endorsed the continuation of the Mars Sample Return (MSR) campaign, the report, and NASA’s actions, left many questions about the long-term future of NASA’s overall Mars exploration efforts. No Mars missions were among the finalists for the flagship missions studied by the decadal survey, unlike the previous decadal survey that backed a Mars rover sample-caching mission called MAX-C that became the Mars 2020 mission, whose Perseverance rover is collecting samples for later return to Earth. The mission, which would orbit the moon to sample its plumes before landing, beat our earlier concepts for a lander to Jupiter’s moon Europa because Enceladus has prominent, steady plumes that Europa lacks, and it lacks the strong radiation environment at Europa that would limit the lifetime of any lander there to weeks, versus years at Enceladus.
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The second-ranked flagship mission is an “orbilander” mission to Saturn’s icy moon Enceladus, which has a subsurface ocean that is potentially habitable. She added that a Uranus mission won out over a Neptune orbiter because the Uranus mission could launch as soon as 2031 with no new technologies required. “Understanding the composition and the properties of either one would revolutionize our understanding of ice giant systems and solar system origins,” said Robin Canup of the Southwest Research Institute, one of the co-chairs of the decadal survey’s steering committee, at an April 19 event to unveil the report. “Mars sample return should be completed as soon as practically possible with no changes in its current design,” said Christensen. At the same time, such ice giants are among the most common exoplanets discovered so far around other stars. Those planets have been visited by only one spacecraft, Voyager 2, in brief flybys, leaving many unanswered questions about them. Juvenile humor aside, the mission to Uranus won the decadal’s endorsement as the top-ranked large, or flagship, mission because of the interest in studying “ice giant” planets like Uranus and Neptune.
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Not only was the decadal recommending that NASA send a mission to Uranus, it was endorsing a Uranus orbiter and probe. The first, and inevitable, reaction to the planetary science decadal survey were jokes, or dread about the inevitable jokes.