Application of terrestrial glints to exoplanet studies
Abstract
Glints, small flashes of reflected light, found in images taken by spacecraft observing the Earth, are generally believed to be due to specularly reflected solar radiation. These glints have been found over both ocean and land. We show that glints over land are due to specular reflection off horizontally oriented ice platelets floating in the air, while glints over ocean have contributions from reflection off both platelets floating above the ocean and ocean waves. Although glints only cover a small proportion of the Earth's surface, they are highly polarized. We use a radiative transfer model to simulate different kinds of glints and to explore their properties. Exoplanets with specularly reflecting materials like icy cloud, surface ice and water could generate light variations that are very different from those with clear atmospheres. For example, rocky, Earth sized exoplanets in the TRAPPIST-1 system are now thought to contain up to 5% of their mass in water (Grimm et al, 2018), which could be observable as clouds, surface oceans or ice. This technique of comparing observations of terrestrial glints with model simulations may provide new information relevant to the search for habitable exoplanets.
- Publication:
-
42nd COSPAR Scientific Assembly
- Pub Date:
- July 2018
- Bibcode:
- 2018cosp...42E1992L