Understanding the climate of our planet Earth is one of the greatest challenges in Science today. Much is still to be learned for example, on the variations of Earths albedo, or on external forcing factors, such as changes in the solar radiation. To truly go in depth into these open questions one may need to step out, view the Earth as a planet and compare it with others to understand dominant external factors that shape our climate over mid and long timescales.
Our Solar System can help to some extent by providing examples of planets under strong greenhouse effect (Venus), planets that have undergone heavy hydrodynamic escape (Mars), and objects with atmospheres similar to ours, albeit much cooler (Titan). But none of these Solar System objects is close to our Earth in its properties. Looking out to other external planetary systems holds the key to placing our planet in its right context. The impact of greenhouse gases, evaluating climates of atmospheres with different chemical compositions, studying the effects of different albedos, understanding the mechanisms of the runaway greenhouse effect, assessing the influence of stellar forcing on planetary climates, can be studied on terrestrial exoplanets, used to add to our knowledge of the climate of the Earth and of natural causes of climate change.
The research field of exoplanet is, within Astrophysics, the one with largest projection over the coming years. With the present proposal we aim at building and consolidating a strong collaboration that can play an important role in this highly competitive field, and establishing strong ties within the already existing Spanish groups, and channeled through the participation in the CHEOPS mission. The CHaracterizing ExOPlanet Satellite (CHEOPS) is the first ESA S-type mission, and will be the first mission dedicated to search for transits by means of ultrahigh precision photometry on bright stars already known to host planets, with an expected launch in mid 2018. By being able to point at nearly any location on the sky, it will provide the unique capability of determining accurate radii for a subset of those planets for which the mass has already been estimated.
We will pave the road for the preparation and exploitation of CHEOPS (and later PLATO and hopefully ARIEL) by conducting scientific research in key areas of (exo-)planetary sciences:
(1) The characterization of the atmospheres of planets in our own Solar System, in particular the Earth and the earthshine;
(2) understanding the Sun-Earth and star-planet connection problems, their atmospheric stellar irradiation conditions and how they can affect their climates;
(3) participating in survey efforts to find the nearest transiting exoplanets around small or bright stars (like K2 or the CARMENES projects);
(4) conducting ground-based studies of exoplanet atmospheres in the optical and near-infrared, which will further our currently very sparse knowledge on the chemical composition and the physical processes of exo-atmospheres;
(5) continuing our work on the CHEOPS, CARMENES, PLATO and ARIEL projects.
