Dr Randall S Perry
Analogues for Ancient Life on Earth
How can we tell if life existed billions of years ago, or if it does or did on Mars, or for that matter how do we define life? Understanding these problems requires a little philosophy of what life is and a lot of chemistry. While we can start from the beginning by looking at the chemical origins of life, another way is to look backwards in more contemporary systems to understand how life's chemical signals are preserved in minerals. One such mineral is silica, and it' found in hot springs such as in the Taupo Volcanic Zone, New Zealand (Fig. 1). Dr. Perry and colleagues are currently studying silica in microbial mats from the Golden Fleece Terrace in Orakei Korako, New Zealand and how they preserve life's chemical signals. Another type of silica is found as a coating on desert rocks, known as desert varnish. Trapped within this varnish are one of the most-
Figure 1. The Orakei Korako geothermal field on the North island of New Zealand discharges water near the boiling point and forms deposits of silica (green, yellow, white areas) fossilizing microorganisms (insert, Scanning Electron Microsope image-
Figure 2. Black coatings of desert varnish on rocks in Death Valley, CA. The coatings are made of silica containing microcolonial fungi (insert, Scanning Electron Microsope image, scale bar is 50 microns) that provide information about past environments.
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