Were the Oceans of Earth Born with the Moon?

The Earth is the lone body in the inner solar system known to have vast quantities of liquid water. Life on our world came about, in part, due to the stabilizing effects the Moon has on our planetary climate. What may seem unusual, however, is that water arrived on Earth at nearly the exact same time the Moon formed. A new study reveals an accidental game of planetary billiards that may have helped define who we are, as a planet.

As our Solar System took shape, roughly 4.5 billion years ago, the planetary disk appears to have divided into dry and wet regions. Water-rich carbonaceous bodies formed in the outer part of the Solar System, while drier, non-carbonaceous objects came into being closer to the Sun. Therefore, examining isotopes (specific varieties) of the silver/white metal molybdenum in meteorites allows researchers to determine the ultimate origin of rocks from beyond our world.

“The molybdenum isotopes allow us to clearly distinguish carbonaceous and non-carbonaceous material, and as such represent a ‘genetic fingerprint’ of material from the outer and inner solar system,” explains Dr. Gerrit Budde of the Institute of Planetology in Münster.

Concentrations of various isotopes of molybdenum in the mantle of the Earth suggest much of the molybdenum located there came from the outer solar system. This idea is entirely consistent with the most-accepted theory for the origin of the Moon.

No, Really, I Think We Should Exchange Insurance Information…

Theia, a body the size of the planet Mars, collided with the young Earth roughly 4.4 billion years ago. Debris from this collision (mostly from the young Earth) fell together, forming the Moon. Chemical analysis of meteorites, performed by a team of researchers from WWU Münster, have now shown that Theia originated in the far reaches of our solar system.

If Theia did form in the cold, dark reaches of the Solar System, this origin could provide additional support suggesting that Theia was mostly solid at the time of impact, while Earth was still partly molten. The greatest collision in the history of our planet would have thus created both oceans and the Moon at the same time. Further impacts by material from the outer solar system would have delivered additional supplies of water to our world.

“Understanding when and how this material was added to Earth is critical for constraining the dynamics of terrestrial planet formation and the fundamental processes by which Earth became habitable,” researchers describe in an article published in Nature Astronomy.

Later on in the formation of the Moon, a body the size of a dwarf planet may have collided with our planetary companion, altering the geology of the lunar surface.

I’ve Always Enjoyed a Place Near the Water…

As we look for signs of life beyond our own world, the moons of the large planets beckon us to search their surfaces. Vast oceans of water are present on three moons of Jupiter, including the largest member of the family, Ganymede, as well as the water world, Europa. The human race will soon be seeing that giant moon up-close and personal, with the Europa Clipper.

Enceladus, orbiting Saturn, holds on to its own sizable stores of water. Titan, the largest moon of the ringed planet, is a world of carbon, the basis of all life. Even tiny Pluto, out in the distant reaches of the planets, may have some liquid water.

In the inner solar system, Mercury is too dry to hold onto water, except small amounts in eternally-shaded craters. Venus has a dense atmosphere, resulting in a runaway greenhouse effect. Surface temperatures on Venus are far too hot for water to exist. The Moon does have water, most of which is hidden in dark craters, like it could be on Mercury. Mars was once a water world, sporting oceans, seas and rivers. But, the Red Planet lost most of its atmosphere and all liquid water long ago. Now, all the water on Mars is found in the form of ice beneath the ruddy crust.

Water may be common in the outer solar system, but the inner solar system appears to be a “dry county.” Let’s be happy that the birth of the Moon was accompanied by something to drink — a toast to Theia!

The Cosmic Companion

Exploring the wonders of the Cosmos, one mystery at a time

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Written by

James Maynard is the author of two books, and thousands of articles about space and science. E-mail: thecosmiccompanion@gmail.com

The Cosmic Companion

Exploring the wonders of the Cosmos, one mystery at a time