Is Milky Way teeming with ‘Earths’? All planets may have been formed by the same building blocks, study says
Scientists are yet to discover alien civilizations that have liquid water and support life. The assumption has been that planets like Earth get their water by chance if a large, ice asteroid hits it. However, researchers now suggest that water may be present during the very formation of a planet. According to their calculations, this is true for both Earth, Venus, and Mars. The findings, which indicate that these planets were created from small dust particles containing ice and carbon, opens up the possibility that planets like Earth with oceans and continents may be abundant in the Milky Way.
Based on their analysis, the team from the GLOBE Institute at the University of Copenhagen believes that Earth may be just one of many planets in our galaxy with continents and liquid water. “All our data suggest that water was part of Earth’s building blocks, right from the beginning. And because the water molecule is frequently occurring, there is a reasonable probability that it applies to all planets in the Milky Way. The decisive point for whether liquid water is present is the distance of the planet from its star,” says Professor Anders Johansen from the Centre for Star and Planet Formation.
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The scientists looked at a theory called “pebble accretion,” which states that planets are formed by pebbles that are clumping together, and that the planets then grow larger and larger. Using a computer model, the team calculated how quickly planets are formed, and from which building blocks.
The analysis shows that it was millimeter-sized dust particles of ice and carbon, which are known to orbit around all young stars in the Milky Way, that 4.5 billion years ago accreted in the formation of what would later become Earth. The findings have been published in Science Advances.
“Up to the point where Earth had grown to one percent of its current mass, our planet grew by capturing masses of pebbles filled with ice and carbon. Earth then grew faster and faster until, after five million years, it became as large as we know it today. Along the way, the temperature on the surface rose sharply, causing the ice in the pebbles to evaporate on the way down to the surface so that, today, only 0.1% of the planet is made up of water, even though 70% of Earth’s surface is covered by water,” explains Johansen.
Using this information, the research team simulated the formation of worlds around other stars. According to the authors, water molecule H2O is found everywhere in the Milky Way galaxy, and the pebble accretion theory thus opens up the possibility that other planets may have been formed in the same way as Earth, Mars, and Venus. They explain that if planets in our galaxy had the same building blocks and the same temperature conditions as Earth, there will also be good chances that they may have about the same amount of water and continents as Earth.
“All planets in the Milky Way may be formed by the same building blocks, meaning that planets with the same amount of water and carbon as Earth, and thus potential places where life may be present, occur frequently around other stars in our galaxy, provided the temperature is right,” the findings state.