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Life May Have Started In The Solar System Before Rocky Planets Like Earth Formed

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The primitive years of the solar system is shrouded in mystery, but could life have existed back then, even when there were no planets?

Scientist Suggests Existence Of Life In Planetesimals

During the Breakthrough Discuss conference at the University of California, Berkeley, on April 11, planetary scientist Lindy Elkins-Tanton from the Arizona State University brought up the suggestion that life may have been around before the planets have finished forming.

After all, Elkins-Tanton pointed out, planetesimals contained all the ingredients necessary for life to flourish even back in the days when the solar system was still forming. It's possible that clement conditions persisted in these planetesimals for millions and millions of years, allowing life to develop.

Planetesimals are the building blocks of planets. It's possible that these small objects may have even made its way to planets such as Earth to seed life that already existed in their cargo. After all, previous research has already theorized that space rocks brought life-giving elements to Earth by crashing on the planet.

"Not all planetesimals are going to be involved in the kinds of catastrophic collisions that would cause them to go into a plasma or otherwise completely denature anything that was created," explained Elkins-Tanton. "Some things are going to fall — like Chelyabinsk, for example — back onto the surface of a temperate planet."

Building Blocks Of Life

Elkins-Tanton, co-author Stephen West, and her students at ASU explored the possibility of life emerging from smaller cosmic bodies. All three ingredients of life are present in planetesimals: liquid water, organic molecules, and energy.

For instance, the radioactive decay of particles inside planetesimals may have provided a heat source that could lead to liquid water and a habitable environment within the rocky object. These environments could persist for millions of years, which is potentially ample time for life to emerge.

Of course, Elkins-Tanton says that her team isn't arguing that life on Earth originated from planetesimals but is simply saying that the possibility exists. It is, as she describes, a thought problem that's worth considering, since even just exploring the potential could give rise to new knowledge about the early stages of solar system.

"Could life actually have arisen on planetesimals? Could there be evidence for life in meteorites that we have not known to look for?" Elkins-Tanton asks. "And if this is so, how could they have been spread through the solar system — and many, many unanswerable implications of that possibility."

As the building blocks of planets, planetesimals are unique cosmic bodies that are of particular interest to scientists like Elkins-Tanton, who also leads the NASA mission to explore the metallic asteroid Psyche, according to Scientific American.

NASA's New Horizons spacecraft completed a flyby of the Kuiper Belt planetesimal Ultima Thule in March. This pristinely preserved rock offers the best opportunity that scientists have ever had to study a planetesimal.

Along with many other features of Ultima Thule, its surface feature evidence of methanol, water ice, and organic molecules. The mission could potentially provide the ideal window for astronomers to understand planetesimals better — and consequently understand early life in the solar system as well.

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