Alien hunters should search for technological life on planets that possess a high oxygen abundance in their atmospheres, according to new research that aims to hone the search for technosignatures from extraterrestrial civilizations. The study from scientists at the University of Roma Tor Vergata in Italy and the University of Rochester in the U.S. argues that a planet's atmosphere needs to contain at least 18 percent oxygen to facilitate a technological civilization. The reason for this, they say, is a simple one: oxygen is needed for fire. This story cites another study detailing a future oxygen-related challenge for the Earth — as the sun ages and brightens in a billion years to produce more heat that warms our planet in turn, Earth's atmosphere will become deoxygenated, with oxygen levels dropping below 10 percent. That study's co-author is Christopher Reinhard, associate professor in the School of Earth and Atmospheric Sciences.