What Would Alien Astronomers Think of Earth? New Study Has an Answer
Sunrise over the Earth
Ever wonder how our planet would look for someone out there? We humans tend to care a lot about what others think of us, but this new study genuinely seems to be looking at Earth from the other side.If aliens were observing our planet, would they be able to tell whether it has life? In a study led by Zurich Department of Physics, scientists found an answer: Yes – but there are conditions.According to the study titled ‘Earth as an Exoplanet: II. Earth’s Time-Variable Thermal Emission and its Atmospheric Seasonality of Bio-Indicators’, finding evidence of life on Earth may depend on the season the hypothetical alien scientists choose to make their observations. To try and look at the planet from outside, Zurich Department of Physics’ doctoral student Jean-Noel Mettler and his fellow researchers studied the infrared emission spectrum and the effect of different observation geometries had on it.”We learnt that there is significant seasonal variability in Earth’s thermal emission spectrum, and the strength of spectral features of bio-indicators, such as N2O, CH4, O3 and CO2 [nitrous oxide, methane, ozone and carbon dioxide] depends strongly on both season and viewing geometry,” the study reads.Four different geometries were examined in the study: the North and South poles, the one centered on the African equator, and one on the Pacific equator. And each point of view provides different results, with scientists concluding that “there is a significant seasonal variability in Earth’s thermal emission spectrum, and the strength of biosignature absorption features depends strongly on both season and viewing geometry.”Aside from seasonal changes that affect observation, it is also about the observing geometries. The variability in readings appeared to be greater above land masses than above oceans.With all the difficulties faced by the researchers, one thing we know for sure: Earth is too dynamic for it to be characterized by a single thermal emissions spectrum. “Using Earth as our test bed, we learnt that a planet and its characteristics cannot be described by a single thermal emission spectrum, but multi-epoch measurements, preferably in both reflected light and thermal emission, are required.”According to the scientists, there is much more to be done.”Future work is required to investigate how cloud fraction, cloud seasonality, and their thermodynamical phase properties affect the detection and result of atmospheric seasonality,” the paper concludes.The perspective provided by the study reinforces the fact that it is important to consider various elements when looking for extraterrestrial life.
