Nancy Huang

Nov 8th 2021

Planet-Forming Disks Contain Key Ingredients for Life: Methanol

The essential ingredients of life as we know include water and carbon. These two substances make DNA, RNA, proteins, fats and sugars, which are part of every living thing. In searching for the possibility of life beyond our planet, scientists have found water elsewhere in our solar system and in other solar systems. The search for carbon has been more challenging, but recent advances in radio telescopes have allowed us to analyze the cloudy disks swirling around young stars to identify molecules that are present as new planets are being born.

Key Molecules of Life

In 2021, the complex carbon molecule methanol was discovered in a developing solar system 320 light-years away, as Nature Astronomy reports. This planet-forming disk around star HD10056 was analyzed by an international team led by Alice Booth of Leiden University (the Netherlands) using the ALMA observatory in Chile. Methanol (chemical formula CH3OH) — also known as wood alcohol — is considered a key molecule of life because it can be used to form more complex organic molecules.

In space, the only efficient way to make methanol is for hydrogen atoms (H) to bond with carbon monoxide (CO) on cosmic dust at temperatures below 20 Kelvin (-423.67 Fahrenheit). Complex carbon molecules have been detected in young solar systems with cooler stars, as explains.

According to Leiden University, the recent discovery around star HD10056 is especially exciting because it was detected in a part of the planet-forming disk that is “warm” at 30 Kelvin (-405.67 Fahrenheit). Methanol cannot form at this temperature, so the large amount detected must be leftover from an earlier cold phase. One possibility is that the methanol formed in a cold interstellar cloud containing just dust, gas and ice, and then survived the heat of that cloud collapsing into a planet-forming disc with a new star at its center.

The abundant methanol detected around the young star HD10056 can be incorporated into planets, moons, asteroids and comets as they are being formed. The available evidence indicates that two giant planets are already present in this solar system. Furthermore, when complex molecules are exposed to ultraviolet radiation from a hot sun, chemical bonds will break and occasionally form more stable and more complex compounds. Therefore, many newly formed planets may start with the essential ingredients of life.

Our Solar System

Scientists are still working to understand how Earth acquired the key ingredients of life. As the Natural History Museum of London describes, our current understanding is as follows: Around 4.6 billion years ago, 99.9% of the material in a swirling cloud of gas, dust and ice coalesced to form our sun. The remaining debris orbited the sun in a flat disc shape and cooled to form solid material. In the high temperatures close to the sun, minerals and metals formed. Farther away, less volatile solids such as ice and ammonia formed. The tiny, dust-like particles bumped into each other, sticking together to form larger particles. They eventually formed planets that swept up the remaining dust and gas in their orbits.

Near the hot sun, the rocky debris gave rise to the four terrestrial planets with metal cores: Mercury, Venus, Earth and Mars. Farther from the sun, the gas and ice giants formed Jupiter, Saturn, Uranus and Neptune. The remaining bits of debris became asteroids (made mostly of metal and rock) and comets (made mostly of ice, dust and rock). Today, many asteroids reside in the asteroid belt between Mars and Jupiter, and many comets reside in the Kuiper belt beyond Neptune.

Special Delivery

In the early days of the solar system, the new planets were constantly bombarded with asteroids and comets. As Smithsonian Magazine shares, it’s believed that these impacts delivered carbon molecules and water from the outer solar system to Earth. These would become the building blocks for life on Earth.

With hundreds of billions of galaxies in the universe, and perhaps 100 billion stars per galaxy, it seems inevitable that there is life elsewhere in the universe. However, while it was once believed that the conditions for life were the result of an almost impossible series of events, new observations suggest that these conditions might be fairly common. Extraordinary new technologies are allowing us to peer into distant galaxies at all stages of development. Thus, the answer to whether there is life on other planets — and where that life might be — may soon come.

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