Darwin To Look For Alien Life 

Equipped with six telescopes, a hub and a satellite, 
an ESA craft will journey into the unknown, reports Biplab Das 

Is earth the lonely outpost of existence? Is there no life elsewhere in the universe? To find out, astrobiologists from the European Space Agency have embarked on an ambitious plan to launch Darwin, a craft that will eavesdrop on other planets for signs of life. By 2014, an Ariane-5 rocket will dispatch Darwin to a remote orbit beyond the moon, 1.5 million km from earth, where it will roam for five years. 

Darwin's eyes are actually six telescopes with a master satellite and a hub. These telescopes will observe in the mid-infrared region of light. Why look in infrared light for signs of life? Life on earth has been around for thousands of millions of years and we have used radio waves for less than a century, but the detection of infrared light is better than trying to look for emission of radio waves, which would only locate intelligent life like ours. By detecting infrared radiation, even the presence of humble life forms like viruses or bacteria can be found. 

Any warm objects, animate or inanimate, emit infrared radiation. On earth, life leaves its imprint in the shape of infrared radiation. On earth, biological activity produces various gases. For instance, plants give out oxygen and animals expel carbon dioxide and methane. These gases, and other substances such as water, absorb certain wavelengths of infrared light. With this clue, an alien eavesdropper armed with infrared light detection equipment can know earth teems with life. In a similar way, Darwin will look for alien life beyond. 

In the 1970s, British scientist James Lovelock pointed out that just by breathing life affects the composition of the earth's atmosphere. "It is better to look for similar effects as a way to search with telescopes for life on other planets," he said. "Thus, you can study the composition of an atmosphere by splitting a planet's light into a rainbow of colours." 

Darwin will look for oxygen, which we know to be closely associated with life. Some life forms use it and some produce it as waste. Without life, all free oxygen in a planet's atmosphere would vanish within just four million years, as it reacts so easily with other chemicals. "The best estimates suggest that Darwin will be able to detect the build-up of oxygen caused within a few hundred million years of life's origin," says Malcom Fridlund, project scientist for ESA's Darwin mission.