Published on: 11/12/2023 (Last updated: 11/12/2023 at: 12:37)
Together – A study found that the oldest continents in our galaxy may have originated 5 billion years before the Earth, meaning that there may be multiple worlds in the Milky Way harboring alien life, more advanced than our own.
Astrobiologists point out that the planet needs certain features to support life: oxygen in its atmosphere, an element that protects living organisms from dangerous radiation, and liquid water, for starters.
Although plate tectonics is not absolutely necessary for life, Earth’s history shows that it is important for organisms to flourish and exist for long periods of time. So, if there were exoplanet continents before Earth, that means there may have been older, more advanced life on that world.
Plate tectonics plays an important role in reducing the Earth’s temperature, as it allows heat to escape from the core, and the presence of a lot of heat in the core would prevent the Earth’s protective magnetosphere. However, some research shows that plate tectonics were not very active billions of years ago when life first appeared. So they may not be necessary for life to begin, but for life to continue and evolve into more complex organisms like humans, they are likely necessary.
These sciences led Jane Greaves, an astronomer at Cardiff University in the United Kingdom, to answer the question: When did the first continents appear on a planet in our galaxy? It turns out that two continents of exoplanets, and perhaps life, likely originated four to five billion years before Earth.
If life on another planet began five billion years ago, it would likely host life more advanced than us, Greaves wrote in a study published in the journal Research Notes of the American Astronomical Society.
Continents are formed due to plate tectonics, which is the movement of rocky plates that float above the molten interior of the planet.
The heat emanating from the planet’s core prevents that magma from solidifying and stops the movement of the continents. This heat comes from radioactive elements, such as uranium-238, thorium-232, and potassium-40, found in the planet’s core, which release energy as they decay.
Most of those radioactive elements came from cataclysmic cosmic events, such as supernova explosions and collisions between the dead crusts of giant stars, known as neutron stars. Traces of these elements can be detected in the wavelengths of light emitted by stars.
In her new work, Greaves used levels of uranium-238 and potassium found in nearby stars, as well as the ages of stars measured by the Gaia satellite, to estimate when a hypothetical rocky planet around each of these stars became hot enough for plate tectonics to appear.
Earth’s plate tectonics began about 3 billion years ago, or about 9.5 billion years since the beginning of the universe. In Greaves’ sample, the first continents appeared two billion years before Earth on thin disk stars. Thick disk stars produced rocky planets with continents that appeared even earlier, about 4 to 5 billion years before the Earth.
“The outlook looks very promising for finding rocky exoplanets with continents, given that nearby Sun-like stars have already produced a few candidate hosts,” Greaves says. “The next step is to study the stellar amounts of thorium and potassium isotopes that cause radiative heating. Doing so could enable “It helps reveal more ancient systems where life could have predated that on Earth.”
