Habitability of the early Earth: Liquid water under a faint young Sun facilitated by strong tidal heating due to a nearby Moon Ren´eHeller · Jan-Peter Duda · Max Winkler · Joachim Reitner · Laurent Gizon Draft July 9, 2020 Abstract Geological evidence suggests liquid water near the Earths surface as early as 4.4 gigayears ago when the faint young Sun only radiated about 70 % of its modern power output. At this point, the Earth should have been a global snow- ball. An extreme atmospheric greenhouse effect, an initially more massive Sun, release of heat acquired during the accretion process of protoplanetary material, and radioactivity of the early Earth material have been proposed as alternative reservoirs or traps for heat. For now, the faint-young-sun paradox persists as one of the most important unsolved problems in our understanding of the origin of life on Earth. Here we use astrophysical models to explore the possibility that the new-born Moon, which formed about 69 million years (Myr) after the ignition of the Sun, generated extreme tidal friction { and therefore heat { in the Hadean R. Heller Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, 37077 G¨ottingen, Germany E-mail:
[email protected] J.-P. Duda G¨ottingenCentre of Geosciences, Georg-August-University G¨ottingen, 37077 G¨ottingen,Ger- many E-mail:
[email protected] M. Winkler Max Planck Institute for Extraterrestrial Physics, Giessenbachstraße 1, 85748 Garching, Ger- many E-mail:
[email protected] J. Reitner G¨ottingenCentre of Geosciences, Georg-August-University G¨ottingen, 37077 G¨ottingen,Ger- many G¨ottingenAcademy of Sciences and Humanities, 37073 G¨ottingen,Germany E-mail:
[email protected] L.