I spent the day at Northrop Grumman, where Alberto Conti (NG Aerospace) convened an intimate workshop on the search for life around other stars. It was a remarkably interdisciplinary day, and I learned a huge amount. An incomplete and personal list of highlights follow.
Tom Vice (NG Aerospace Systems President) and Tom Pieroneck (NG) opened up the meeting by talking about hard problems, which is a good way of thinking about building an engineering team that will have work to do for many years; I realized that it is hard problems in data analysis that unites a lot of what we do at Camp Hogg; it attracts good students, postdocs, and collaborators.
Sara Seager (MIT) kicked off the science talks with a completely eye-opening discussion of how we might identify signs of life through spectroscopy. She emphasized that there are many possible false-positive signals. But it would be exciting if we found oxygen, water, and methane in the same atmosphere. The discussion of water-based life vs other liquids. She made a strong case for water! Another great idea (maybe from Lee Feinberg in the audience?) was to look for signs of climate change to identify life!
Sanjoy Som (Blue Marble) gave a great and surprising talk about how we might use the geological record of rocks on Earth to look at life signatures and changes to our atmosphere over time. The coolest was his use of fossilized raindrops, plus some first-year mechanics. His point: The different states of Earth through time are proxies for exoplanets with life. Great point!
Leslie Rogers (Berkeley) talked about inferring planet masses and mass–radius relationships. In a direct-detection experiment we will measure neither directly; is that a problem? In the question period, someone brought up the possibility that it would be the moon of a giant planet in the habitable zone that might be the inhabited object.
Chris Stark (STScI) produced mind-blowing simulations of all possible ExoHab or LUVOIR missions to find habitable planets. His simulations include optimizations of target ordering, exposure time, for starshade and coronographic experiments, all as a function of things like mirror size, mission lifetime, and so on. So much input! He made the comparison to the LHC: We need a mission that produces an interesting answer even if it doesn't detect life signatures. That is a good point. He mentioned that we will be affected by exo-Zodiacal light at unknown levels; we need to figure this out before we settle on final design decisions for anything. Fortunately, this may be addressable from the ground or with WFIRST.
There were so many other interesting things, in talks and discussions: Karin Öberg (CfA) talked about the formation of planets and the chemical and materials properties of the disks in which planets formed; Daniel Apai (Arizona) talked about mapping planet surfaces with time-domain lightcurves (something he has done to great effect); Alicia Berger (Colorado) talked about amino acids and their relationship to biosignatures. In that latter talk, Öberg burst one of my bubbles by noting that despite claims in the literature, amino acids have not been discovered in interstellar spectra. A great day!