Can Abigail Allwood Find Life On Mars?

She made her name identifying the earliest accepted proof of life on Earth. Now NASA is counting on her to repeat the trick.

- Laura A Parker

From 2003 to 2005, when Abigail Allwood was a graduate student in earth science at Macquarie University, in Australia, she made a series of remarkable discoveries. She was doing fieldwork in the country’s Pilbara region, where she was charged with studying fossilized stromatolites, or columns of sedimentary rock originally created by layers of microbes—some of the planet’s first known life.

The area, a 196,000-square-mile expanse of rust-colored desert populated with rock formations dating back more than 2 billion years, is more or less what you might picture when someone says “the ends of the Earth.” Parts of it remain virtually untouched by humans. Allwood recalled for me recently how one day she and Ian Burch, then her research partner (now her husband), hiked the length of a high, narrow ridge some 10 miles long. “I’m pretty sure we were the only people that had been there for thousands of years,” she told me. “I remember a northern quoll [a ratlike marsupial native to Australia] coming right up to us to take a closer look. It had never seen a human being before, so it wasn’t afraid.”

Even more exciting than the native fauna, however, were the geologic formations Allwood and Burch had come to study. They resembled stacks of upside-down ice-cream cones—a pattern typical of stromatolites, which usually form in shallow water. Their presence suggested that this part of the desert was once a very wet area, perhaps an ocean reef. Before long, Allwood would establish that the rocks constituted the oldest known evidence of life on Earth.