![]() ![]() Even an understanding of the planet's star is imperative, to know whether it provides steady, nourishing light or unpredictable blasts of harmful radiation. Knowing that the planet's average temperature supports liquid water is a start, but the length of the planet's day and seasons and its temperature extremes count, too. ![]() Finding a specific gas-oxygen, say-in an alien atmosphere isn't enough without figuring out how the gas could have gotten there. Instead, context and multiple lines of evidence will be key to a detection of alien life. There is unlikely to be a single smoking gun. To prepare for the coming flood of exoplanet data, and help telescope designers know what to look for, researchers are now compiling lists of possible biosignatures, from spectral hints of gases that might emanate from living things to pigments that could reside in alien plants or microbes. But they will be able to sample light from a range of other planets, and astronomers are already dreaming of a space telescope that might produce an image of an Earth-like planet as good as Kane's pixelated views of Earth. The new generation of space telescopes heading toward the launch pad, including NASA's mammoth James Webb Space Telescope (JWST), have only an outside chance of probing an Earth twin in sufficient detail. But astronomers hope that a true Earth twin, bursting with flora and fauna, would reveal its secrets to even a distant observer.ĭetecting them won't be easy, considering the meager harvest of photons astronomers are likely to get from such a tiny, distant world, its signal almost swamped by its much brighter nearby star. Kane says he and his colleagues are trying to figure out "what we can expect to see when we can finally directly image an exoplanet." Their exercise shows that even a precious few pixels can help scientists make the ultimate diagnosis: Does a planet harbor life?įinding conclusive evidence of life, or biosignatures, on a planet light-years away might seem impossible, given that space agencies have spent billions of dollars sending robot probes to much closer bodies that might be habitable, such as Mars and the moons of Saturn, without detecting even a whiff of life. The images are a glimpse into a future when telescopes will be able to just make out rocky, Earth-sized planets around other stars. Kane took images from the Deep Space Climate Observatory satellite, which has a camera pointing constantly at Earth from a vantage partway to the sun, and intentionally degraded them from 4 million pixels to just a handful. He knows his findings are correct because the planet in question is Earth. They are enough for him and his colleagues to conclude that the planet has oceans, continents, and clouds. Yet Kane, an astronomer at the University of California, Riverside, has tracked subtle changes in the pixels over time. The images are just a few pixels across and nearly featureless. ![]() Stephen Kane spends a lot of time staring at bad pictures of a planet. ![]()
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