Study: alien astronomers may mistake the Earth for an uninhabited planet

New studyEarth as an Exoplanet II. Earth's Time-Variable Thermal Emission and its Atmospheric Seasonality of Bio-Indicators shows that the detection of evidence of life on Earth may depend on the season observed by alien astronomers.

Lead author, Jean-Noel Mettler of ETH Zurich, notesthat when studying exoplanets, scientists measure ultraviolet and infrared radiation, which makes it possible to learn about the properties of planetary atmospheres, surfaces, and the overall energy balance. A similar approach should be taken with respect to the Earth, if one ever studies it from the depths of space.

With this approach, the potential habitability of the Earth can only be proven under certain conditions.

The study looked at four different observing geometries and analyzed thermal spectra using an atmospheric infrared probe aboard NASA's Aqua satellite. Data from different positions differed greatly, not always corresponding to the conditions considered favorable for the development of life.

The general conclusion from this study is that a living, dynamic planet such as the Earth cannot be characterized by a single spectrum of thermal radiation. Too many different processes take place on the planet, and this complexity makes the remote characterization of the Earth a very difficult task.