The recent US Decadal Survey (Astro2010) contains a conundrum.
As part of the report, the Decadal Survey committee identified three key “scientific objectives” on which they felt the community should focus. These were:
- “Cosmic Dawn: Searching for the First Stars, Galaxies, and Black Holes”
- “New Worlds: Seeking Nearby, Habitable Planets”
- “Physics of the Universe: Understanding Scientific Principles
(For the record, I think this is a completely reasonable list, filled with the kinds of things that make splashy magazine covers. It’s arguably tilted a bit far from more traditional but critically important aspects of astronomy — for example, we don’t actually know how stars form, or how they explode, and yet the only bit of stellar physics that’s covered under this list is the fossil record of the absolute lowest metallicity stars. However, the committee had to narrow things down, and these are certainly the most “sellable” aspects of our field, as far as congressional committees and the general public is concerned.)
Now, these key questions are supposed to be partial guides to the project prioritization that the committee carried out. And yet, when you look at the list of recommended space- and ground-based investments, there really is precious little that is deeply connected to #2. As many have commented here and elsewhere, where is the investment in exoplanets?
While I agree it appears to be a glaring conflict, I think it’s actually completely sensible. The search for extrasolar planets is by far the hottest new area of astronomy. However, because it’s so new, the scientific landscape is wide open and barely explored. Is the most interesting question the mass function and radial distribution of planets? Are the subset of habitable planets the most compelling targets? Is the study of atmospheres and exoplanet weather the big breakthrough issue? What about the theory of stability of planetary systems? Do we know the physics controlling how all these planetary systems form? Every single one of these questions is awesome, but it would be nuts to take bets now on a billion dollar flagship facility dedicated to just one of these topics.
I’m guessing that what the committee did was essentially try to earmark some of the explorer-class space and ground missions for exoplanets. They made exoplanets an unambiguous scientific priority, and then they did their best to protect pots of money for faster timescale moderate-sized experiments (2nd ranked for both ground and space). Thus, when an exoplanet mission is proposed for an Explorer satellite, they get the huge boost of saying that their satellite will help answer one of the key questions from the Decadal Survey. (Edit: They also called out for investment in “New Worlds Technology” (i.e., things like a steerable sunshade) that would reduce the price of a mission to study habitable planets in the future, putting an exoplanet-optimized flagship mission at a fundable price point in time for the next decadal survey.) This strategy is smart — we’ve got Kepler up right now, JWST in the nearish future, and on-going ground-based work across the world. The field is evolving so rapidly, that it’s almost certainly better that the experimental response be kept as nimble as possible. So, reading the tea leaves, I think exoplanets did just fine in this report.