Lynn Margulis (1938-2011)

She was a bold thinker undaunted by the condescension that comes with the promotion of ideas ahead of their time.  The unifying thread in her career was symbiosis -- the way that organisms work together to survive, and eventually evolve so dependent on each other that they can be considered a single organism.  

She argued for over a decade before it was accepted that the human cell is composed of a symbiotic relationship amongst formerly independent organisms.  This position was fantastically vindicated when it was discovered that the mitochondria in your cells have their own DNA different from yours, proving that they are essentially a primitive, unrelated species of unicellular life. Without mitochondria your cells would simply not work; they are as much a part of you as your blood or nerves.

She controversially extended this symbiotic view of life not just down to the cellular level, but out to the global level.  She championed the Gaia Hypothesis that the biosphere itself acts, in many ways, as a single organism that can manipulate itself and its environment -- the Earth -- to regulate and perpetuate itself.  An analogy might be an ant colony:  composed of thousands of autonomous units, but practically functioning in many was like a single organism.

There are a few connections to astrobiology for Dr. Margulis -- Gaia Theory and her work on early cellular evolution help to inform the search for life on other planets (what should we be looking for? how robust is it?), and of abiogenesis (how did the first life and cells form?).  

Dr. Margulis was a member of the National Academy of Sciences and received the National Medal of Science in 1999.  She was a University Professor of Geology at UMass Amherst.

Remarkably, she was married to Carl Sagan for a while (whom the Times article linked to above mistakenly refers to as a "cosmologist" -- he was a planetary scientist).  Talk about a power couple!