Where did the Moon come from? A new theory | Sarah T. Stewart

Summary

A planetary scientist explores the origins of the Earth and Moon, challenging the conventional giant impact theory. Through innovative experiments and simulations, they discover a new type of astronomical object called a 'synestia,' formed when a planet spins so fast it breaks the rules of being a planet. The Moon, they propose, formed inside a synestia, explaining the Earth-Moon connection. This groundbreaking theory shifts our understanding of planet formation and the history of our solar system, highlighting the importance of questioning assumptions and embracing new ideas.

Takeaways

• 😀 The speaker, a planetary scientist, discusses their favorite activity: simulating planet collisions to understand planetary formation.
• 😀 The 'giant impact theory' posits that the Moon formed from debris after a Mars-sized body collided with Earth, but it has a major flaw regarding the isotopic similarity between the Earth and Moon.
• 😀 The Earth and Moon have identical isotopes, suggesting they were made from the same materials, which challenges the giant impact theory.
• 😀 No other planetary bodies share the same isotopic relationship as the Earth and Moon, making them 'twins' in a way that no other planets are.
• 😀 The scientist and their team struggled to find a better theory than the giant impact hypothesis, but they eventually realized that changing the spin of the Earth could explain the Moon's formation.
• 😀 Simulations of fast-spinning giant impacts showed that it is theoretically possible to make a disk from the same materials as the planet, but this scenario was highly unlikely.
• 😀 The breakthrough came when the scientist realized that their assumptions about the formation of planets were wrong, leading to the discovery of a new type of astronomical object: the synestia.
• 😀 A synestia is a massive, hot, rotating object formed when a planet's surface vaporizes due to the extreme heat and spin caused by a giant impact.
• 😀 In the new theory, the Earth became a synestia after the impact, and the Moon formed inside this vaporous body, explaining their isotopic similarity.
• 😀 Synestias are not stable for long and eventually cool down and shrink, turning back into planets over time. The formation of the Moon could have occurred during this transformation process.

Q & A

What is the primary theory about the origin of the Earth and Moon?

The leading theory for the origin of the Earth and Moon is called the 'giant impact theory.' This theory suggests that a Mars-sized body struck the young Earth, and the Moon formed from the debris disk around the planet.

What is the flaw in the giant impact theory?

The giant impact theory predicts that the Moon should be mostly made from the Mars-sized impactor. However, both the Earth and Moon have identical isotopes, suggesting that they are made from the same materials, which contradicts the theory's prediction.

Why are the Earth and Moon considered 'identical twins'?

The Earth and Moon are considered 'identical twins' because they have the same isotopes. This means that their materials are nearly identical, which is highly unusual since other planets have distinct isotopic signatures.

What did the scientist and his team initially propose to explain the special relationship between the Earth and Moon?

They proposed that changing the spin of the Earth after the giant impact might mix more material, making it possible for the Earth and Moon to have identical isotopes.

What breakthrough did the scientist make when analyzing the data from fast-spinning giant impacts?

The breakthrough came when the scientist realized that after a giant impact, the Earth doesn’t remain a planet in its usual form. Instead, it becomes a completely new object, which led to the discovery of 'synestia,' a new type of astronomical object.

What is a synestia, and how is it formed?

A synestia is a new type of astronomical object formed when the heat and spin from a giant impact cause a planet to lose its spherical shape. The material at the planet’s equator spreads into a disk, and the planet becomes a highly deformed, vaporized object that is not quite a planet anymore.

How does a synestia help explain the formation of the Moon?

The Moon likely formed inside a synestia, which is a vaporized and highly deformed version of Earth after a giant impact. As the synestia cooled, the Moon grew from the magma rain that condensed out of the vapor, explaining the isotopic similarity between Earth and the Moon.

What is the significance of the new theory about synestias in planetary science?

The discovery of synestias offers a new way to solve the problem of the Moon’s origin, providing a mechanism that accounts for the isotopic similarities between Earth and the Moon. It also challenges previous assumptions about planetary formation and the aftermath of giant impacts.

What was the challenge the scientist faced when confronted with the strange object in the data?

The scientist faced the challenge of understanding a strange new object that didn't resemble a planet or a normal disk. It led to the realization that the planet was not behaving as expected, and that the object formed by the giant impact was something entirely new—leading to the discovery of synestia.

How does the scientist suggest we approach the unknown in scientific discovery?

The scientist advocates for questioning assumptions, being willing to throw away old ideas, and creating mental space for outrageous new ideas. By playing with these ideas and testing them against real-world data, new discoveries can be made.