'Sniffing Out' Extraterrestrial Life

We’ve looked for E.T. but haven’t seen him, and we’ve listened but haven’t heard him, so now scientists are working on a plan to see if they can “sniff” him out.

It’s not exactly as though they expect to detect his under-tentacle deodorant. Instead, they hope to inhale a few molecules on some distant celestial body and see if those molecules are specific proteins that bear the clear signature of life.

Library of Life

It’s all the brainchild of Marilyn Fogel, senior scientist at the Carnegie Institution of Washington, and she has a lot of work laid out for her in the years to come. First, she has to build a complete library of heavy molecules, such as proteins, here on Earth. Then, she needs to show which molecules resulted from non-biological processes and which are proteins that show the presence of life.

“This will be five years of work,” Fogel says, and that’s just for the first stage. After completing her “library,” Fogel expects a device similar to the one she is using for her ambitious project to be shipped off to Mars or some other object in our solar system to see what it can find.

It all began about three years ago when she was a member of the Space Studies Board of the National Research Council, the research arm of the National Academy of Sciences. The board was being briefed by NASA on plans to bring back a sample from Mars to see if it contained any evidence of life.

“This was very disturbing to me,” she says, because she thought NASA had put the cart before the horse. It would make more sense, she concluded, to come up with some sort of gadget that could do the same thing while still on the surface of Mars.

Without doing that first, she asked NASA, how could you know which samples were worth bringing back?

It would also be a lot cheaper than hauling a bag full of rocks back from Mars that might turn out to be of little value. But unfortunately no one knew just how to isolate and analyze proteins on the surface of Mars without shipping an entire laboratory to the Red Planet.

A DNA Nose

So Fogel set out to find a way to do just that. She knew she needed something similar to DNA microchips that can do thousands of reactions on a very small surface, but she needed it to work on proteins, the building blocks of life. All living tissue contains proteins.

As luck would have it, a California firm, Ciphergen Inc., was developing an instrument for biomedical research that could fill the bill. The instrument, which became available just last year, consists of tiny, thin strips of metal coated with different chemically active molecules that can extract and identify other molecules, including proteins, from complex mixtures.

Think of it as a hypersensitive nose.

Such a device, Fogel believed, could “sniff out” the clues she was looking for.

She wrote a proposal that was immediately accepted by NASA’s National Astrobiology Institute, an interdisciplinary consortium at the Ames Research Center south of San Francisco that is dedicated to the search for extraterrestrial life. The equipment is now at Carnegie’s Geophysical Laboratory in Washington, D.C.

“I’m right at the beginning, and I think it’s very exciting,” says Fogel, an astrobiologist who has spent many years studying how molecules are affected by biological processes.

The device, called a “time of flight mass spectrometer,” isolates molecules, and then separates them according to weight. Some molecules are very light, such as amino acid. A typical protein consists of a chain of amino acids, and is thus much heavier.

Amino acids are essential for life to form, but their presence doesn’t necessarily mean life is there. The presence of protein, on the other hand, indicates that amino acids have combined to form the basic structure of organic life.

So it’s those larger molecules, or proteins that bear the clear signature of life.

Misleading Molecules

But nature can be tricky, as evidenced by the on-going debate over whether tiny rod-shaped crystals found in the Martian meteorite ALH84001 were formed by geology or biology. Some heavy molecules can be formed by non-biological processes, and sorting out which molecules resulted from which process is the task that now stretches before Fogel.

The problem, as she sees it, is “we don’t even have a complete inventory of proteins here on Earth,” so that’s the starting point.

“What I intend to do with this instrument is look at things like organic matter from meteorites, organic matter that comes from my colleagues here who are doing abiotic [not produced by living organisms] synthesis experiments” as well as proteins that are an essential part of the cells of every living substance, she says.

In a few years, she hopes to have a complete catalogue of which molecules were formed by which processes, and how they changed through fossilization.

Then, maybe in a decade, the instrument in her lab could be downsized to the microchip level and sent off to Mars, or possibly Jupiter’s moon Europa, to search for proteins there. If it finds them, Fogel believes she can compare them to samples in her library and determine their role in a very different world.

Then, at least, we’ll know what we should be looking for.

Lee Dye’s column appears weekly on ABCNEWS.com. A former science writer for the Los Angeles Times, he now lives in Juneau, Alaska.

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