How the Earth Was Made: Birth of the Earth, 2009, 720p

Summary

The documentary reconstructs Earth’s early history using meteorites, ancient rocks, lunar samples, and living microbial structures. It portrays Earth as a planet shaped by impacts and geological change, with several key milestones.

Formation and growth

About 4.567 billion years ago, dust and gas around the young Sun began clumping together. An experiment aboard the International Space Station, in which salt grains stuck together in microgravity, offered a possible model for how tiny mineral grains could aggregate. The growing rocky bodies eventually included one that became Earth.

Melting and layering

Repeated impacts and heat from radioactive materials are presented as causes of the young Earth melting. Dense iron and nickel sank to form the core, while lighter material formed the mantle and crust. The surface cooled into a crust, though impacts and volcanism continued.

Dating Earth

Because erosion and tectonic activity have erased most of Earth’s earliest rocks, geologists used meteorites as evidence. Radiometric dating of meteorite samples led to an estimated Earth age of 4.567 billion years.

The Moon’s origin

A theory proposed by Bill Hartmann holds that a Mars-sized body struck the early Earth, ejecting rocky outer material that later formed the Moon. The Moon’s relative lack of iron compared with Earth is presented as evidence supporting this giant-impact explanation.

Early crust and oceans

Amphibolite rocks at Porpoise Cove in northern Canada were dated to about 4.28 billion years old. Their mineral and chemical signatures suggest that Earth already had a substantial crust and oceans at that time. Banded iron formations found in the same ancient sequence provide further evidence of underwater conditions.

Water and life’s building blocks

A meteorite that fell in 1998 contained ancient salt crystals with tiny droplets of liquid water. The documentary presents meteorites as a likely source of Earth’s water. The Allende meteorite and others also contain amino acids, chemical building blocks of life, suggesting that some ingredients for life arrived from space.

Oxygen and changing geology

Stromatolites are structures formed by communities of microbes, including oxygen-producing cyanobacteria. Around 3.5 billion years ago, cyanobacteria began releasing oxygen through photosynthesis. Over geological time, this oxygen transformed the atmosphere and helped make complex life possible.

Living organisms also contributed to the formation of rocks and fossil fuels, including limestone, chalk, coal, oil, and gas.

Evidence and methods

The documentary describes several ways scientists investigate Earth’s early history:

• Use radiometric dating to determine the ages of rocks and meteorites.
• Examine meteorite interiors and mineral contents for clues about the early solar system.
• Analyze ancient rocks’ mineralogy and chemical signatures to infer where and how they formed.
• Use the iron content of lunar rocks to assess theories about the Moon’s formation.
• Study fluid inclusions in meteorite salt crystals as evidence for ancient water.
• Observe modern stromatolites and cyanobacteria to understand how early microbial life affected Earth’s atmosphere.

Researchers and sources featured

Researchers and individuals

• Don Pettit — Astronaut who conducted the salt-grain experiment aboard the International Space Station.
• James Ussher — Archbishop whose biblical chronology placed Earth’s creation in 404 BC.
• Ernest Rutherford — Physicist associated with using radioactive decay to date rocks.
• C. C. Patterson — Geologist who dated meteorites to estimate Earth’s age.
• Bill Hartmann — Proposed the giant-impact explanation for the Moon’s formation.
• O’Neil — Geologist who studied the ancient rocks at Porpoise Cove; no first name is given in the subtitles.
• Zalinsky — Researcher discussing water-bearing meteorites; no first name is given in the subtitles.
• Seaford — Researcher discussing stromatolites and cyanobacteria; no first name is given in the subtitles.
• Charles Duke — Apollo astronaut shown collecting a lunar rock sample.

Evidence sources and locations

• Meteorites, including samples from Meteor Crater, Arizona, and the Allende meteorite.
• Apollo 16 lunar samples held at the Johnson Space Center.
• Ancient amphibolites and banded iron formations at Porpoise Cove, northern Canada.
• Living stromatolites at Cuatro Ciénegas, northern Mexico.
• The International Space Station salt-grain experiment.