What Would Earth Look Like to Alien Astronomers in the Age of Dinosaurs? --New Research Models History of Earth's Climate
What would Earth look like to alien astronomers in the Age of the Dinosaurs? Two astronomers from Spain -- Enric Palle and Esther Sanroma, of the Astrophysical Institute of the Canary Islands (IAC)--are modeling the clouds at different periods in Earth's past to better understand what alien worlds might look like in different stages of their evolution. The results of their reserach would not only reveal how Earth would look to a distant observer, but could also help astronomers determine the layout of landforms on alien planets.
“When you look at the planet...it has a given distribution of continents and clouds,” said Enric Palle, of the Astrophysical Institute of the Canary Islands (IAC) in an interview with Astrobio.net“But it has not always been the same.”
The team looked back in time to measure how much the brightness of the planet would vary as the continents of Earth shifted 90, 230, 340, and 500 million years ago, when the planet had a different layout. They decided not to look farther back, because Earth's atmosphere has only had a similar temperature and composition for the last half billion years.
Five hundred million years ago, there were huge swings in the light as the planet rotated each day. The variations were four times as large as changes in other periods.The authors attribute this to two causes.
First, the land masses were closer together, rather than spread out, leaving wider expanses of oceans. These result in a wildly different cloud distribution. Second, the land half a billion years ago was all desert, completely bare of all life.
”Five hundred million years ago is the time in which life evolved from oceans to land,” Palle said.As plants began to cover the land, the cloud arrangement shifted. The advent of life brought changes that would have made Earth more difficult to examine from space. “We camouflaged ourselves, and made it more difficult for a distant observer to characterize the Earth,” Palle said.
The process could work in reverse - a light curve with small changes could potentially indicate vegetation on another planet. However, stronomers studying an exoplanet would need more information before they could definitively reach such a conclusion.
Rather than relying on climate modeling to predict how clouds would behave, Palle and Sanroma decided to base their modelling on the assumption that wide global patterns would continue in the past, with clouds behaving the same way over oceans and deserts as they do today.“Big cloud patterns, on a global scale, are tied to the continental distribution and ocean circulation,” Palle added.
By applying this pattern to other time frames, they were able to calculate how widely the brightness of Earth would change over the course of its daily rotation. According to Palle, a new approach was necessary to look so far back in time. By focusing on the patterns of clouds over land and ocean, Sanroma and Palle hope to overcome the uncertainties that crop up in climate modeling.