The P-T mass extinction that almost cleared the planet of life 250 million years ago may have been instigated by populations of algae dying. According to one group of scientists, this die-off of large numbers of relatively simple life forms caused a crash in the ocean’s entire food web. As part of the Astrobiology: Exobiology and Evolutionary Biology program at NASA, the team of scientists will now be exploring signs of an early algae die-off about 1.5 million years before the main P-T extinction event.