“When you arise in the morning, think of what a precious privilege it is to be alive — to breathe, to think, to enjoy, to love.” –Marcus Aurelius
How old is life on Earth? If all you had to go on was the fossil record, you’d run into severe trouble once you went back more than one or two billion years, as all your rock would have metamorphosed, making examination and identification of fossils impossible. But recently, we’ve discovered another method: to measure the isotopic content of carbon deposits in ancient rock formations.
Hadean diamonds embedded in zircon/quartz, some of which date to over 4 billion years old. Image credit: Martina Menneken, Alexander A. Nemchin, Thorsten Geisler, Robert T. Pidgeon & Simon A. Wilde, via http://www.nature.com/nature/journal/v448/n7156/fig_tab/nature06083_F3.html.
The carbon-12 to carbon-13 ratio is a surefire signature of life, and tells us that life on Earth goes back at least 4.1 billion years: 90% of the age of our planet. Could this be the hint we’ve needed to conclude that life on Earth actually predates the Earth itself?
Organic molecules are found in interstellar space in many varieties. Image credit: NASA / JPL-Caltech / T. Pyle; Spitzer Space Telescope.
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