科学美国人60秒:E.T. May Reveal Itself with Vibration

When we look for life beyond Earth, we usually search for its chemical signatures. The recent discovery of methane emissions on Mars, for example, is a possible sign of bacterial life. But there IS another way to detect life. See if it moves. 

"Everything moves. [laughter] I'm looking for something that I know that should be alive and does not move, but up to now I have not seen anything like this." Giovanni Longo, a physicist at the École Polytechnique Fédérale in Lausanne, Switzerland. “It’s extremely interesting, because it gives us a possible new definition of life if you want. If it moves, then it's alive."

Longo and his colleagues studied the movements of bacteria, yeast, mouse, human and plant cells, using the nanosensor in an atomic force microscope. And they found that every living cell they studied vibrated in tune with the metabolic processes going on inside. When they altered bits of the cells' metabolism, the vibrations changed; when they killed the cells in the sample chamber--the vibrations stopped. The findings appear in the Proceedings of the National Academy of Sciences. [Sandor Kasas et al, Detecting nanoscale vibrations as signature of life] 

Using their nanosensor search technique, the researchers were able to detect the vibrations of life in soil and water samples, too. So why not do the same thing on Mars? An atomic force microscope has in fact already been sent there, on the Phoenix Lander, though it wasn't set up to do these types of analyses. "But it can be done, so next time they can just modify it a little bit." And in doing so - expand our suite of life-detecting tools.

—Christopher Intagliata