杏吧原创

This is the inner solar system as it might appear to alien astronomers. It proves we could one day see surface features like oceans, continents, giant storms, and signs of life on Earth-like exoplanets with powerful future telescopes.

We have taken a few direct images of Jupiter-sized exoplanets, but doing the same for an Earth-scale world would require a space telescope with a mirror hundreds of metres in diameter. James Webb, NASA鈥檚 much-delayed next space telescope, is only 6.5 metres wide.

That isn鈥檛 stopping some people from getting ready now. 鈥淚 can imagine in my children鈥檚 generation we can build such a telescope on the surface of the moon鈥� says Jonathan Jiang at NASA鈥檚 Jet Propulsion Lab in Pasadena, California, whose team created the image.

Powerful telescope

Even such a powerful telescope would only be able to see distant worlds as a single pixel. In an attempt to figure out what we could learn from such a telescope, Jiang and colleagues used data from the Deep Space Climate Observatory (DSCOVR), a spacecraft that monitors changes in our Earth鈥檚 ozone, vegetation and climate.

DSCOVR is known for snapping 鈥�selfies鈥� of Earth from more than 1.5 million kilometres away. The team averaged two years of observations across various wavelengths of light into a series of single point images, akin to what聽Jiang鈥檚 imagined lunar telescope would see when looking at an alien world.

By re-analysing the different frequencies of light contained in these dots, the team were able to recover the 24 hour cycle of night and day on Earth. They were also able to approximate the proportion of sea, land, vegetation, ice and rock, along with seasonal changes in cloud coverage.

Jiang sees his experiment as a baseline to help develop real telescopes, including one that could search directly for signs of life. A telescope that collects the right wavelengths would be able to detect the presence of oxygen, and could therefore look for daily or seasonal cycles from a photosynthesising alien world.