Life could have started on carbon-based planets, study finds

Rather than forming on Earth-like planets made of silicate rocks and iron cores, extraterrestrial life may have originated on carbon-based planets comprised of diamond or graphite, researchers from the Harvard-Smithsonian Center for Astrophysics (CfA) reported in a new study.

Writing in the Monthly Notices of the Royal Astronomical Society, lead author Natalie Mashian, a graduate physics student at Harvard, and her colleagues went on to explain that these life-supporting worlds could be discovered by searching for an extremely rare class of stars.

“This work shows that even stars with a tiny fraction of the carbon in our solar system can host planets,” Mashian, who worked on the study along with PhD thesis advisor, Avi Loeb, explained in a statement. “We have good reason to believe that alien life will be carbon-based, like life on Earth, so this also bodes well for the possibility of life in the early universe.”

The findings could strengthen the notion that alien life exists somewhere beyond our planet and our solar system, according to Wired UK, and that astronomers might be able to find it simply by searching for an ancient type of star known as a carbon-enhanced metal-poor (CEMP) star.

Studying CEMP stars may shed new insight on planetary formation

As the CfA researchers explain, the primordial universe lacked chemical elements such as carbon and oxygen, both of which are essential for life as we know it, and consisted mainly of hydrogen and helium. It wasn’t until the first stars went supernova, providing additional resources required for planet formation, did it become possible for these organisms to survive.

CEMP stars, however, contain just one hundred-thousandth as much iron as is found in our sun, meaning that they formed before interstellar space became seeded with these heavy elements. Despite this, they tend to contain higher amounts of carbon that one might expect due to their age, and this relative abundance would influence planet formation, the authors said.

These carbon-rich worlds, should they exist, would be difficult to tell apart from planets that are more like the Earth when it comes to their mass and physical size, the CfA astronomers said. The only way to tell them apart would be to analyze their atmospheres in search of gases like carbon monoxide and methane. If they exist, however, they could provide new insight into how planets (and possibly biological life) originally formed in the aftermath of the Big Bang.

“These stars are fossils from the young universe. By studying them, we can look at how planets, and possibly life in the universe, got started,” Loeb explained. Searching for these stars by using the transit method could be a “practical” way to discover “how early planets may have formed in the infant universe,” he added.

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Image credit: Christine Pulliam (CfA). Sun image: NASA/SDO

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