A new study suggests a bit of cosmic good fortune in the form of a massive nearby explosion may have been instrumental in preventing Earth from transforming into a hostile ocean world.
The research, published in the journal Nature, focuses on the earliest days of our solar system, when our sun was extremely young and surrounded by rocky bodies known as planetesimals. These building blocks of future planets, rich in abundant ices, are believed to have played a large role in delivering water to Earth.
Ultima Thule, an icy primordial object visited by NASA's New Horizons spacecraft in January, is an example of such a planetary building block frozen in time.
According to the study, too much of a good thing can be a big problem for planets inundated with ice-rich planetesimals.
"But if a terrestrial planet accretes lots of material from beyond the so-called snowline, it receives way too much water," lead author Tim Lichtenberg, who performed the research as a doctoral student at the Institute of Geophysics of ETH Zürich in Switzerland, said in a statement.
These so-called "water worlds," believed common throughout the universe, are generally covered in deep global oceans and feature an impenetrable layer of ice on the ocean floor. According to the scientists, the very geochemical processes that gave birth to Earth's life-supporting climate and surface conditions — such as the carbon cycle — are doused on drowned planets.
A fortuitous explosion
To discover why our solar system, and specifically Earth, wasn't drowned in its early water-rich past, Lichtenberg and his team developed computer models that simulated the formation of thousands of planets and their planetesimals. Along with other scientists, they believe a supernova from a nearby dying star nearly 4.6 billion years ago showered our early solar system with radioactive elements like aluminium-26 (Al-26).
As it decayed, the AI-26 heated and effectively dehydrated the planetesimals prior to their gradual buildup into protoplanets.
"The results of our simulations suggest that there are two qualitatively different types of planetary systems," summarizes Lichtenberg. "There are those similar to our solar system, whose planets have little water. In contrast, there are those in which primarily ocean worlds are created because no massive star, and so no Al-26, was around when their host system formed. The presence of Al-26 during planetesimal formation can make an order-of-magnitude difference in planetary water budgets between these two species of planetary systems."
The researchers believe the study's findings could aid future space telescopes, such as the upcoming James Webb, in the search for exoplanets located in regions rich in star-formation and, consequentially, AI-26.
"These will bring humanity ever-closer to understanding whether our home planet is one of a kind, or if there are an infinity of worlds of the same kind as our own," they add.