“All planets in the Milky Way can be formed by the same building blocks, which means that planets have the same amount of water and carbon as the earth,” says Professor Anders Johansen. Credit: NASA, ESA and G. Bacon (STScI)
According to a new study from the University of Copenhagen, Earth, Venus, en March is made of small dust particles that contain ice and carbon. The discovery opens the possibility that the Milky Way can be filled with water planets.
Astronomers have long looked to the vast universe in hopes of discovering alien civilizations. But for a planet to have life, liquid water must be present. The chance of the find scenario seems impossible to calculate, as it was the assumption that planets like Earth accidentally get their water when a large ice steroid hits the planet.
Now, researchers from the GLOBE Institute at the University of Copenhagen have published a striking study that suggests that there may be water during the formation of a planet. According to the calculations of the study, this applies to Earth, Venus and Mars.
‘All our data indicate that water was part of the Earth’s building blocks from the beginning. And because the water molecule occurs frequently, there is a reasonable probability that it applies to all planets in the Milky Way. The crucial point of whether liquid water is present is the distance of the planet from its star, ”says Professor Anders Johansen of the Center for Star and Planet Formation, who led the study, which is published in the journal Science Advances.
Are all planets formed by ice?
Anders Johansen and his team calculated using a computer model how fast planets are formed and from which building blocks. The study indicates that it is dust particles of ice and carbon millimeters in size – known to orbit all young stars in the Milky Way – that increased 4.5 billion years ago in the formation of what would later become Earth.
‘Up to the point where the earth has grown to one percent of its current mass, our planet has grown by trapping masses of pebbles filled with ice and carbon. The earth then grew faster and faster until after five million years it became as big as we know it today. Along the way, the temperature on the surface rose sharply, causing the ice in the pebbles to evaporate on its way down to the surface, so that today only 0.1 percent of the planet is made up of water, although 70 percent of the earth’s a surface is covered by water, ”says Anders Johansen, who ten years ago, together with his research team in Lund, presented the theory that the new study now confirms.
The theory, called “pebble growth”, is that planets are formed by pebbles that clump together, and that the planets then get bigger and bigger.
Anders Johansen explains that the water molecule H2O occurs everywhere in our galaxy, and that the theory therefore opens up the possibility that other planets can be formed in the same way as Earth, Mars and Venus.
‘All planets in the Milky Way can be formed by the same building blocks, which means that planets with the same amount of water and carbon as the earth – and therefore potential places where there may be life – regularly occur around other stars in our galaxy, provided the temperature is right, ”he says.
Good chances for the origin of life
If planets in our galaxy had the same building blocks and the same temperature conditions as the earth, chances are they would have about the same amount of water and continents as our planet.
Professor Martin Bizzarro, co-author of the study, says:
‘According to our model, all planets get the same amount of water, and this indicates that other planets not only have the same amount of water and oceans, but also the same amount of continents as here on earth. It offers good opportunities for the origin of life, ”he says.
If, on the other hand, the amount of water on planets is random, the planets may look very different. Some planets would be too dry to develop life, while others would be completely covered by water.
“A planet covered with water would, of course, be good for maritime beings, but offer less than ideal conditions for the formation of civilizations that the universe can observe,” says Anders Johansen.
Anders Johansen and his research team are looking forward to the next generation of space telescopes, which offer much better opportunities to observe exoplanets orbiting a star other than the Sun.
‘The new telescopes are powerful. They use spectroscopy, which means that by noting what kind of light from the planets’ orbit around their star is blocked, you can see how much water vapor there is. It can tell us something about the number of oceans on that planet, ”he says.
Reference: “A Klippie accretion model for the formation of terrestrial planets in the solar system” by Anders Johansen, Thomas Ronnet, Martin Bizzarro, Martin Schiller, Michiel Lambrechts, Åke Nordlund and Helmut Lammer, 17 February 2021, Scientific progress.
DOI: 10.1126 / sciadv.abc0444