“Foust Forward” appears in every issue of SpaceNews magazine. This column ran in the Sept. 10, 2018 issue.
How much is it worth to answer one of humanity’s biggest questions? That’s a topic that astrophysicists, NASA and Congress will have to grapple with in the next few years.
On Sept. 5, a committee of the National Academies released their final report on an “Exoplanet Science Strategy,” a document requested by Congress in the 2017 NASA authorization act. The report makes recommendations for future research to discover and analyze exoplanets, including determining if any may be habitable.
The committee of scientists who prepared the report were optimistic about the future of the field. Advances in the last decade have shown that exoplanets in general are common, including those roughly the size of the Earth and in orbits that would allow liquid water to exist on their surfaces.
Those scientists concluded that it’s only a matter of time, and funding, before they either find evidence of life on exoplanets or conclude such life must be rare. “If we choose, we could learn the answer to that question — we could figure out whether or not there’s life on planets orbiting other stars — in the next 20 years,” said committee co-chair David Charbonneau at a briefing about the report at the National Academies in Washington.
Most of the recommendations in the report involve spacecraft and observatories already in development, from using the James Webb Space Telescope to study exoplanet atmospheres and continuing work on the Wide Field Infrared Survey Telescope to providing financial support for two large ground-based telescopes.
Its top recommendation, though, called for development of a new large space telescope able to directly image Earth-sized exoplanets and perform spectroscopic observations to identify the presence of biosignatures like oxygen, water and methane. Such a telescope could be ready by the mid-2030s if recommended by the next astrophysics decadal survey, scheduled for completion in late 2020.
NASA is already funding studies of two such missions, called HabEx and LUVOIR, in preparation for the decadal survey. The two, though, are very different. HabEx features a mirror 4 meters across — larger than WFIRST but smaller that JWST — devoted to exoplanet research. LUVOIR’s current concept calls for a telescope with a primary mirror up to 15 meters across, but intended for use throughout astrophysics.
The new report made no attempt to pick one over the other, or to discuss costs at all. “We do not feel it is up to us to decide where in that buffet of options the mission architecture should be,” said the committee’s other co-chair, Scott Gaudi. Either mission could meet that recommendation, he said, and it should be the decadal survey committee that makes a final choice after seeing completed mission designs and cost estimates.
But even if the decadal survey does recommend HabEx or LUVOIR (two other concepts less useful to exoplanet science, Lynx and Origins, are also being studied), exoplanet scientists may still have an uphill battle with NASA and Congress. Earlier this year NASA asked the teams working on each of those concepts to develop a second, less expensive option, likely through the use of smaller mirrors or fewer, less sophisticated instruments.
The problems with WFIRST and JWST in particular will make it difficult for whatever concept the decadal survey selects as its highest-priority flagship mission. It may be especially difficult for LUVOIR, which looks like a scaled-up JWST. What confidence will Congress have that this time will be different when it comes to staying on budget and schedule?
The scientific and even cultural payoff, though, could be immense if that mission ultimately does find evidence of life on exoplanets. Can you put a dollar value on finding out if we’re not alone in the universe? The federal government might, in effect, be asked to do that when it considers what next big astrophysics mission to develop after WFIRST.
Jeff Foust writes about space policy, commercial space, and related topics for SpaceNews. His Foust Forward column appears in every issue of the magazine.