Science & Technology: Martian Territory ; If There Is Life on Other Planets, How Will We Find It? Marcus Chown Meets a Team of Scientists in Chile Who Say They Have the Answer
Chown, Marcus, The Independent (London, England)
Picture the scene: a desolate, alien-looking plain, cowering beneath a blistering sun. In the middle of the plain a robotic vehicle, about the size of a Mini Cooper, is trundling along at a slow walking pace, as it has been ever since the sun came up a few hours ago. It stops at a scarred, wind-scuffed rock. Lights flash, cameras whirr. Then it moves on.
Cut to Mission Control, a darkened room in Pittsburgh. It's late evening. A dozen excited scientists crowd round monitors showing the wind-scuffed rock. The atmosphere is tense as they examine the image, pointing at spectral data scrolling down the side of the screen. Finally, a cheer goes up. It's official. They've found it " life on Earth!
Earth? Yes, the alien plain is actually in the Atacama Desert of Chile, probably the dryest place on Earth. You would be forgiven for thinking it was the surface of another planet " like Mars. But this is precisely the point: the scientists and engineers behind the robotic rover are testing the technology they hope will one day be used on a world like Mars.
'If you can't detect life in the most inhospitable place on Earth, what chance will you have on Mars?' says Alan Waggoner, an Atacama team member and the director of the Molecular Biosensor and Imaging Center at the Carnegie Mellon University in Pittsburgh. Waggoner and his colleagues are one of several teams developing schemes to detect life on other worlds, with the backing of Nasa's Astep (Astrobiology Science and Technology for Exploring Planets) programme.
The project is headed by the Carnegie Mellon Robotics Institute for the technology part, and by the Nasa Ames Research Center/Seti Institute. It involves experts in robotics, plus geologists, chemists, physicists and, of course, biologists.
If you're going to look for life on another planet, you need a good definition of life. No such definition exists, although most can agree on life's central characteristics " the ability to reproduce, move around, compete for resources, pass information from generation to generation, and so on.
Waggoner and his colleagues look for four of the chemical 'building blocks' of life " DNA, the genetic material; proteins, the scaffolding and chemical engines of cells; lipids, the molecules of cell walls; and carbohydrates, the fuel of life.
Waggoner is an expert in fluorescent biosensors " molecules that can be attached to target biological molecules and which, when illuminated, 'fluoresce', or give out characteristic flashes of light. They are usually used to show the chemical pathways in cells. 'But it's also an ideal technology for detecting life on another planet,' Waggoner says.
The rover, christened Zoe, uses four fluorescent dyes, which attach to DNA, proteins, lipids and carbohydrates respectively. When it stops at an interesting location, these are sprayed on the ground beneath and allowed to soak in for a few minutes. When the ground is lit up with artificial light from Zoe, the dyes that have found their targets fluoresce.
The difficulty is that the solar-powered rover has to 'rove' in bright daylight, making it hard to detect the fluorescence. The solution is to illuminate the ground with an intense but ultra- short pulse of light, and to open the shutter of the rover's camera for the same interval. …