Using radiometric dating, scientists have determined that the Earth is 4.54 billion years old (with an uncertainty of less than 1%). The first 600 million years of the Earth’s history are known as the Hadean Eon (from Hades, the Greek god of the underworld) — when the Earth resembled Dante’s Inferno (minus the colorful cast of characters), a hellish place, scattered with volcanoes belching hot lava, gases, and ash. Since there were no webcams or Google driverless cars recording all this red-hot activity, the earliest objects discovered by scientists in the last decade provide a unique window into the formation of the planet and evolution of life.
Oldest crystal: 4.4 billion years
A tiny crystal composed of zircon was discovered in a sheep ranch near Perth Australia back in 2001. Scientists using atom-probe tomography were able to accurately date the crystal, publishing their results in the journal Nature Geoscience (February, 2014). The ancient crystal, a mere 400 micrometers long, is translucent red and glows blue when bombarded with electrons. The crystal is the earliest confirmed piece of the earth’s crust. The ratio of oxygen isotopes contained in the crystal suggest that the Earth’s temperature 4.4 billion years ago would have supported liquid water and, most likely, life (note that the earliest fossils are about 3.5 billion years old).
Oldest rock: 4.33 billion years
In the eastern shore of the Hudson Bay, in northern Quebec, geologists discovered the earth’s oldest rocks in a section of bedrock, known as the Nuvvuagittuq (pronounced “NOO-voo-AG-it-tuck”) greenstone belt, that is the only surviving portion of the Earth’s crust formed during its nascence. The Nuvvuagittuq rocks are composed of cummingtonite-plagioclase-biotite-garnet magic amphiboles (truly, a geological mouthful; and for those with a prurient curiosity, “cummingtonite” is actually a scientific term for a metamorphic amphibole composed of magnesium iron silicate hydroxide — so there!). By measuring the levels of the isotopes samarium and neodymium, considered rare earth elements, the rocks were dated between 3.8 to 4.33 billion years. The results were published in the journal Science (September, 2008). Geologist Richard Carlson stated the value of the findings: “[Study of these ancient rocks] gives us an unprecedented glimpse of the processes that formed the [Earth’s] early crust.”
Oldest skeleton: 55 million years
Palaeontologists discovered the oldest skeleton, a tiny tree-dwelling primate, known as Archicebus achillus, in a quarry located in the Hubei Province of central China in 2013. Archicebus belongs to the evolutionary tree’s branch that leads to modern apes, monkeys, and humans; and critically, near the point where monkeys and apes split into two separate groups. About the size of a human hand, the creature looks like a pygmy mouse lemur with monkey features — it has a long tail, with teeth, hands, and feet like a monkey. Like other primates, the feet have long, large toes with nails. It is only a matter of time, of course, before Disney creates a film franchise based on the adorable Archicebus. The palaeontologists published their results in the journal Nature (June, 2013). The lead scientist explaiend the importance of the find: “Archicebus marks the first time that we have a reasonably complete picture of a primate close to the divergence between tarsiers and anthropoids. It represents a big step forward in our efforts to chart the course of the earliest phases of primate and human evolution.” Great news, now pass me the banana.
For further reading: The Oldest Living Things in the World by Rachel Sussman, University of Chicago Press (2014)
The Age of the Earth by G. Brent Dalrymple, Stanford University Press (1991)