U.S. plans for Mars should include more than sample return, report warns | Science

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U.S. plans for Mars should include more than sample return, report warns | Science

NASA has fallen behind on its launch cadence for Discovery missions such as Insight, which took flight in May.

JPL-CALTECH/NASA

NASA needs to prepare for future trips to Mars that go beyond an upcoming mission to collect rock samples and eventually return them to Earth, the National Academies of Sciences, Engineering, and Medicine (NASEM) reported today. The new report provides a midpoint assessment of how the agency’s planetary science programs have performed since NASEM’s 2011 decadal survey, which recommended priorities for 2013 to 2022.

The report largely lauds NASA for acting on many science priorities while navigating a budget lower than the worst-case scenario envisioned by the 2011 decadal. Financing for research and technology development has remained high and the agency has made substantial progress on two multibillion-dollar flagship missions: the Mars 2020 rover, set for launch in 2 years; and the Europa Clipper, set to explore Jupiter’s frozen moon and the ocean of liquid water inside it next decade.

The $2.4 billion Mars rover will inaugurate what has been the long-standing, highest priority of planetary science: returning rock samples from Mars to Earth to hunt for signs of past life. The rover will drill samples and leave them cached on the martian surface for retrieval. Last year, after years of delay, the agency began to lay out a plan for how to get them back, envisioning a “skinny” sample return that would send several additional missions to the planet over the next decade to retrieve the rock cores.

The midterm review, which was given the additional task of assessing NASA’s Mars Exploration Program, found the sample return plans sensible and endorsed them. However, overall the review panel found NASA’s plans for Mars disjointed, more a series of unrelated missions rather than a coherent program. “Right now, the Mars program really needs to be reassessed as far as direction,” says Louise Prockter, director of the Lunar and Planetary Institute in Houston, Texas, and co-chair of the committee that conducted the study.

In particular, the panel worried that the communications infrastructure around Mars, which relies on three NASA orbiters, could fail before successor spacecraft are in place. “We are concerned that the infrastructure is aging, it is fragile,” Prockter says. Given the panel’s limited role of evaluating only existing projects and plans, they could not recommend a new orbiter, Prockter added. “But that is one solution [NASA] should probably be considering.” The agency could also seek a commercial partner to provide such a telecommunications relay, a “tantalizing prospect” that the agency mentioned this past year, says G. Scott Hubbard, a space scientist at Stanford University in Palo Alto, California, who reviewed the report and previously lead NASA’s Mars program.

Many planetary scientists who don’t work on the Red Planet remain jealous of the attention, and financing, it has commanded in recent decades. But exploration of Mars is unlikely to stop with sample return, and NASA needs to be strategic about its next steps, Hubbard says. The scientific assets already on the planet keep revealing new mysteries. For example, the recent “detection by radar of a liquid ‘lake’ near the south pole is tremendously exciting,” Hubbard says. “New missions with radar or missions to study the polar regions of Mars could be enormously scientifically productive.”

The report also warns that NASA is unlikely to reach its desired launch cadence for Discovery and New Frontiers, its two largest programs that hold open competitions for mission funding. Discovery funds missions that cost up to about $450 million, whereas New Frontiers has an $850 million cap. The decadal had recommended selecting Discovery missions every 2 years; to meet that goal, it notes, NASA would have to select three more proposals for flight by 2022. Meanwhile, if another New Frontiers mission is not selected, two potential concepts targeted for proposals—a network of four geophysical landers to probe the moon’s interior and a spacecraft to explore Jupiter’s volcanic moon, Io—would not get a fair shot at consideration before the next decadal review. “That was the main casualty of the low budget that we had the start of the decade,” Prockter says. “It remains to be seen whether NASA will get back on track.”

The panel only glances at another prominent reason for these delays: a push by a prominent lawmaker for a mission to the jovian moon Europa, adds Stephen Mackwell, the corporate director of science programs at the Universities Space Research Association in Columbia, Maryland, who reviewed the report prior to publication. Representative John Culberson (R–TX), a member of the House of Representatives appropriations panel who has been critical in boosting NASA’s budget in recent years, has accelerated funding for the Europa mission—and a potential lander to follow—moving it ahead of other missions. In contrast, the decadal survey would have delayed the Europa mission in favor of competitively awarded missions. “It needs to be clear that NASA didn’t capriciously step away here,” Mackwell says.

Although Congress has ordered NASA to start work on a Europa lander, such a mission proposal has not yet been through the agency’s formal cost and technical evaluation process; similar evaluations prompted both the Mars 2020 rover and Europa Clipper to shrink their costs and scientific ambitions. The next decadal will need to pull the proposed Europa lander through a similar evaluation, the midterm warned.

The panel also faulted a recently completed report studying the third most important large-scale scientific objective of the planetary scientists, a potential mission to Neptune or Uranus, which have so far only been explored through flybys by Voyager 2 decades ago. The report, prepared by NASA’s Jet Propulsion Lab in Pasadena, California, altered the scientific objectives outlined in the decadal, it said; it also added a Doppler imager to study the planet’s interior, a less-tested instrument that, if it failed, could jeopardize the project’s science goals. NASA should redo the study, the panel said, this time keeping its focus on the decadal science objectives.

The panel also suggested means to improve the decadal process. For example, the agency should get started now supporting a bevy of new mission concepts for the next decadal to consider. And the agency, the panel recognized, needs a nimble way to respond to new discoveries or technologies—for example, it says, the 2011 decadal was overtaken by the rise of small satellites and revelations about Saturn’s plume-spewing frozen moon, Enceladus. Last year, NASEM’s planetary committee adjusted its charter to consider such issues at NASA’s prompting; for example, it is now mulling how the agency’s plans to return to the moon align with its long-term science goals.

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