Earth is the only planet whose composition and characteristics scientists know in detail, and the only world where life is confirmed. To improve the search for life elsewhere, researchers at the University of Washington have created a virtual version of Earth without organisms, which can be used to compare the planet with more than 6,000 known exoplanets.
Earlier virtual Earth models represented the planet’s core, mantle and crust. The new model also includes the atmosphere and surface, two areas that are important when assessing whether a planet could support life. It tracks Earth from its formation about 4.5 billion years ago through to a point 500 million years in the future.
The model initially represents Earth using geological characteristics alone, without accounting for life. Comparing this lifeless version with the real, inhabited planet can reveal atmospheric differences that may serve as signs of biological activity. Many gases in Earth’s atmosphere, for example, are produced by living organisms.
The team’s first tests of the model have produced promising results. Researchers plan to apply it to exoplanets, particularly rocky worlds that resemble Earth. They will enter measurements gathered by telescopes, including each planet’s mass, radius and orbit, as well as the radiation and composition of its star. The model will then estimate what the planet’s atmosphere might look like without life.
If that estimate matches the atmosphere observed by space-telescope spectrographs, the measurements would be consistent with a lifeless planet. Differences could point to biological activity and make the exoplanet a candidate for further study. One example is the simultaneous presence of methane and oxygen: the gases destroy one another, so their continued coexistence could suggest that organisms are replenishing them.
The virtual Earth could also help guide the design of space telescopes. For work on the Habitable Worlds Observatory, researchers modelled Earth at different geological periods and simulated how a telescope might observe it. Such simulations can help determine which wavelengths instruments should measure and how much detail their images need to capture. Different stages of Earth’s history produce different atmospheres, and therefore different requirements for detecting signs of life.
Sources: Xataka.