On the Effects of the Evolution of Microbial Mats and Land Plants on the Earth as a Planet. Photometric and Spectroscopic Light Curves of Paleo-Earths

Abstract

Understanding the spectral and photometric variability of the Earth and the rest of the solar system planets has become of the utmost importance for the future characterization of rocky exoplanets. As this is not only interesting at present times but also along the planetary evolution, we studied the effect that the evolution of microbial mats and plants over land has had on the way our planet looks from afar. As life evolved, continental surfaces changed gradually and nonuniformly from deserts through microbial mats to land plants, modifying the reflective properties of the ground and most probably the distribution of moisture and cloudiness. Here, we used a radiative transfer model of the Earth, together with geological paleo-records of the continental distribution and a reconstructed cloud distribution, to simulate the visible and near-IR radiation reflected by our planet as a function of Earth's rotation. We found that the evolution from deserts to microbial mats and to land plants produces detectable changes in the globally averaged Earth's reflectance. The variability of each surface type is located in different bands and can induce reflectance changes of up to 40% in period of hours. We conclude that using photometric observations of an Earth-like planet at different photometric bands, it would be possible to discriminate between different surface types. While recent literature propose the red edge feature of vegetation near 0.7 µm as a signature for land plants, observations in near-IR bands can be equally or even better suited for this purpose.

On the Sensitivity of the Devonian Climate to Continental Configuration, Vegetation Cover, Orbital Configuration, CO 2 Concentration, and Insolation

“…We note, however, that the soil albedo value used in Le Hir et al () is very high; given the early presence of microbial mats (Boyce & Lee, ) which have a much lower albedo (Sanromá et al, ) than the one used in Le Hir et al (), our low value for the soil albedo is better suited to represent rocks covered with microbial mats and therefore appears to be more plausible.…”

Theoretical Reflectance Spectra of Earth-like Planets through Their Evolutions: Impact of Clouds on the Detectability of Oxygen, Water, and Methane with Future Direct Imaging Missions

“…Previous studies have modeled the reflectance spectra of modern Earth-like planets considering the effect of clouds in the atmospheres (e.g., Des Marais et al 2002;Tinetti et al 2006a,b;Robinson et al 2011;Kitzmann et al 2011;Rugheimer et al 2013;Sanromá et al 2013;Kitzmann et al 2013;Sanromá et al 2014;Rugheimer et al 2015a;Feng et al 2018;Wang et al 2018). In addition to modern Earth-like planets, Kaltenegger et al (2007) and Rugheimer & Kaltenegger (2018) modeled the reflectance spectra of planets similar to the Earth at earlier geological epochs orbiting around Sun-like stars, and those around F, G, K, and M stars, respectively.…”

Geology and Photometric Variation of Solar System Bodies with Minor Atmospheres: Implications for Solid Exoplanets

“…For this purpose, Earth, among others, has been of significant interest in terms of habitability, and its diskintegrated spectrum has been studied both observationally (e.g., Arnold et al, 2002;Woolf et al, 2002;Hamdani et al, 2006;Turnbull et al, 2006;Livengood et al, 2011) and theoretically (e.g., Ford et al, 2001;Des Marais et al, 2002;Tinetti et al, 2006aTinetti et al, , 2006bKaltenegger et al, 2010;Robinson, 2011;Robinson et al, 2011). Spectra of the Earth at different evolutionary stages have also been modeled by changing the bioactivity (Kaltenegger et al, 2007;Sanromá et al, 2013) and continental distribution (Sanromá and Pallé, 2012).…”