How to Search for Ice Age Aliens
Could an alien astronomer have detected life on Earth during an ice age?
Recent work has calculated how past climate extremes affected the light reflected from vegetation out into space. The results could give hope to our own search for life on distant worlds. From far away, our planet is a single faint speck of light in the sky. Although we have sent radio messages out to potential extraterrestrial listeners, none of these signals have traveled more than a few tens of light years. However, Earthlings have been broadcasting their presence to the galaxy for millions of years. Terrestrial plants reflect strongly in the infrared, resulting in a distinctive feature (called the vegetation red edge or VRE) in the light bouncing off the Earth's surface. "We know from earlier works that vegetation was detectable in the contemporary spectrum, but was vegetation visible when the Earth was much colder than today?" wonders Luc Arnold from the Observatory of Haute Provence in
Arnold and his colleagues have taken climate models from a recent ice age, as well as a recent warm period, and used them to generate the reflection spectrum of the Earth in times past.
Their result that was published in the International Journal of Astrobiology shows that the VRE has remained a relatively constant interstellar beacon over the millennia.
Kemo D. 7