« Characterising transiting planet atmospheres through 2025 » is the ambitious title of a report written by the “Exoplanet Exploration Analysis Group” mandated by NASA. The lead author is Nick Cowan, who’s realised some nice work on exoplanet atmospheres (see for instance here).
A short time ago, I wrote an update on the status of space missions for the study of exoplanet atmosphere, taking stock of the non-selection of the dedicated Echo and FINESSE missions. The James Webb Space Telescope (JWST), Hubble’s successor, is the only space instrument able to study exoplanet atmospheres planned for the 2020-2025 years.
The report by NASA’s working group makes the case for a space mission dedicated to atmosphere observations for transiting planets, using a 1-meter space telescope. The telescope would cover visible and near-infrared wavelengths, and carry out a survey of up to 1000 nearby transiting planets. The mission would realise a wide survey of atmospheres from hot Jupiters to super-Earths (Earth-size planets remain out of reach in transit even for the next generation of instruments), while the JWST would be able to concentrate on a few key targets.
The project corresponds, in all its fundamental characteristics, to ESA’s defunct Echo proposal. Cheekily, Echo is not mentioned even once in the report. This might be due to the bittersweet legacy it has left: the lead scientist of Echo was associated with highly doubtful claims on exoplanet atmospheres.
Most of the best targets for the proposed space mission are still to be identified by upcoming surveys, including NASA’s TESS survey missions that might be launched in 2017. Except in the case of a catastrophic failure of these surveys, the targets should be available by 2020.
Signal estimates suggest that a 1-m dedicated space mission could provide solid data for hot Jupiters and hot Super-Earths, some indications on warm Neptunes, and a few tentative indications on temperate super-Earths. Initial estimates predict that TESS could identify about 4 temperate super-Earths transiting sufficiently bright stars.
Unlike Echo proposals, this report does not identify the identification of bio-markers in the atmosphere of habitable planets as an objective, which is more in line with previous experience and realistic expectations. To quote the report: “These measurements will be unlikely to conclusively establish or refute the habitability of these worlds, but would lay the ground-work for future flagship missions.”