We are studying Earth's paleoclimate and paleogeography as a base model to characterize future observations of Earth-like exoplanets. We are particularly interested in interpreting the diurnal and seasonal light curves variations (reflected light), which are strongly influence by the distribution of land and ocean masses. Earth-like planets will potentially show measurable changes in brightness as they rotate while planets with dense atmospheres, like Venus, will not show variations. Therefore, future observations of Earth-like planets will be able to at least recognize planets with land and oceans, or even (luckily) determine the percent coverage of each. Other spectral observations will complement these observations by measuring the chemical composition of their atmosphere and search for potential biosignatures.
We are using terrestrial global paleogeography reconstructions to model Earth-like exoplanets. A spinoff of this study is the Visible Paleo-Earth Project, a more educational and artistic project. As a preliminary step of this study, we are also developing a program to analyze the distribution of land and ocean masses from paleomaps. The program was done with IDL and is available upon request. Figures 1-7 show the output analysis for seven periods: Today, 20, 65, 240, 370, 450, and 500 million years ago. Later, we will add more periods. The results are very interesting, and some of this analysis was done before, but we still need to validate the numbers with previous studies. For example, the figures show that oceans in our planet remained between 70 to 80% coverage in the last 500 million years while land areas moved predominantly from south to north.
The figures are divided in four frames, a context paleomap in an equirectangular projection with annotated percent coverage of ocean and lands areas, including how the land is divided between the northern and southern hemisphere (a), the latitudinal distribution of land areas every 15 degrees (b), the simultaneously viewable land area from space as a function of longitude (c), and the longitudinal distribution of land areas every 30 degrees (d). To better appreciate the view from space, here are orthographic projections for some of the periods.
Figure 1. Earth Today.
Figure 2. Earth 20 Mya during the Early Miocene.
Figure 3. Earth 65 Mya during the KT Boundary.
Figure 4. Earth 240 Mya during the Late Triassic.
Figure 5. Earth 370 Mya during the Late Devonian.
Figure 6. Earth 450 Mya during the Late Ordovician.
Figure 7. Earth 500 Mya during the Late Cambrian.