“The search for planets is the search for life,” said Natalie Batalha, a Kepler mission scientist at NASA’s Ames Research Center. In the search for habitable Earth-like planets, sometimes something really strange appears, something different from anything in our solar system.
The “era of exoplanets” officially began in October 1995, when Nobel laureates Michel Mayor and Didier Queloz revealed the first discovery of a planet outside our solar system, an exoplanet, orbiting a solar-type star in our home galaxy, the Milky Way, planet 51 Pegasi b, a gaseous ball comparable to the largest gas giant of the solar system, Jupiter. Their discovery started a revolution in astronomy and more than 4,100 exoplanets have been found in the Milky Way since then. And strange new worlds are discovered almost every day.
“Extremely extreme life” of the Milky Way
One of those weird “something” was announced by a team of researchers from Arizona State University (ASU) and the University of Chicago with a new study published in the Planetary Science Journal. The team determined that some carbon-rich exoplanets, given the right circumstances, could be made of diamonds and silica. “These exoplanets are unlike anything in our solar system,” says lead author Harrison Allen-Sutter of the ASU School of Earth and Space Exploration.
When stars and planets form, they do so from the same gas cloud, so their mass compositions are similar. A star with a lower carbon / oxygen ratio will have planets like Earth, made up of silicates and oxides with very small diamond content (Earth’s diamond content is about 0.001%).
But exoplanets around stars with a higher carbon / oxygen ratio than our sun are more likely to be carbon-rich. Allen-Sutter and co-authors speculated that these carbon-rich exoplanets could convert to diamond and silicate if water (which is abundant in the universe) were present, creating a diamond-rich composition.
“Island Worlds”: a totally new frontier of exoplanets
Test the hypothesis
To test this hypothesis, the research team needed to mimic the interior of carbide exoplanets using high heat and high pressure. To do this, they used high-pressure diamond anvil cells at co-author Shim’s Lab for Earth and Planetary Materials. First, they immersed the silicon carbide in water and compressed the sample between the diamonds at a very high pressure. Then, to monitor the reaction between silicon carbide and water, they conducted laser heating at the Argonne National Laboratory in Illinois, taking X-ray measurements as the laser heated the sample to high pressures.
As expected, with high heat and pressure, the silicon carbide reacted with water and turned into diamonds and silica.
“Proof of existence”
Some astronomers have argued that it is irrelevant whether or not there are other life forms discovered in the Milky Way or other galaxies. The fact that we are here provides “proof of existence” as it is called in mathematics. But so far the research continues. Planetary scientists and astrobiologists are using sophisticated tools in space and on Earth to find planets with the right properties and the right position around their stars where life could exist.
“The nearby alien planets may be in the” Early Earth “stage of life” – Carl Sagan Institute
For the carbon-rich planets that are the focus of this study, however, they probably lack the properties necessary for life. Although the Earth is geologically active (an indicator of habitability), the results of this study show that carbon-rich planets are too difficult to be geologically active and this lack of geological activity can render the atmospheric composition uninhabitable. Atmospheres are critical to life as they provide us with air to breathe, protection from the hostile environment of space, and even pressure to allow liquid water.
“Regardless of habitability, this is another step to help us understand and characterize our ever-increasing and improving observations of exoplanets,” says Allen-Sutter. “The more we learn, the better we will be able to interpret new data from upcoming future missions such as the James Webb Space Telescope and the Nancy Grace Roman Space Telescope to understand the worlds beyond our solar system.”
The Daily Galaxy, Sam Cabot, via Arizona State University
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