Micrometeorites in the Post-lunar Greenhouse Effect

Abstract

On the Earth, an astonishing balance between the absorption and scattering of solar radiation by the early Earth produced the remarkable benign greenhouse effect favourable to the origin and evolution of life. Indeed, the first constraint on any scenario is that the early oceans were not boiling or freezing! It is generally considered that the temperature has to be sufficiently high to prevent freezing at a time when the solar luminosity was smaller than today. But it has to be kept sufficiently low by some mysterious feedback effect, in order to protect the Earth from a runaway greenhouse effect, which led to a surface temperature of about 450 °C on Venus. In fact, the long-lasting micrometeorite thermospheric volcanism effective after the Moon-forming impact, should have ruled the post-lunar greenhouse effect that was critical for the birth of life. Indeed, this impact eradicated at once all atmospheric ingredients of the pre-lunar greenhouse effect at a time when the young Earth was already almost fully outgassed. Subsequently, micrometeorites released simultaneously greenhouse gases for heating and smoke particles for cooling. These micrometeorite ashes resided temporarily within a kind of giant thermospheric cocoon, which might have functioned as a self-regulating IR heater during the period of low solar luminosity. Indeed, it was simultaneously heated up from the inside through the aerodynamical braking of micrometeorites.