Unearthing the Destructive Power of Unstable Moons in Eradicating Alien Life in the Universe

The fall of the moon to Earth may seem like an unrealistic apocalypse scenario, but for some planets in other star systems, such catastrophic collisions may be commonplace.

In a new study published in the journal Monthly Notices of The Royal Astronomical Society has used computer simulations to show that collisions between exoplanets and their moons could actually be a common occurrence, which would be a disaster for any alien life emerging on these planets.

Although astronomers have not reliably detected exomoons, they expect there to be many of them in the universe.

“We know about many satellites in our solar system, so naturally we expect to see satellites in exoplanetary systems,” says Jonathan Brand, an astrophysicist at the University of Kansas who was not involved in the new study. Brad Hansen, an astronomer at the University of Kansas, California, Los Angeles and author of the new study, is interested in understanding how moons and exoplanets interact and how these interactions affect the possibility of life in distant star systems.”

Gravity governs the interaction between the planet and its moons, manifesting itself in the form of tides and other effects such as the tidal slowing of our Moon.

Each year, the Earth’s moon moves away from our planet by a little more than an inch, and its orbit increases every year.

Meanwhile, the Earth rotates a little more slowly every year. These two effects are directly related, so that the Earth gives up some angular momentum from its rotation to the Moon’s orbit.

And if this trade-off continues long enough, the Moon may eventually come loose with the Earth. Luckily for us, this process will take a long time before the Sun explodes long before the Moon can completely withdraw. But around some exoplanets, especially those that are much closer to their stars than the Earth is to the Sun, this situation can develop much faster, because, according to Hansen’s calculations, the planets and their “unstable” satellites collide during the first billion years of their formation. (For comparison, the Earth and Moon are about 4.5 billion years old.)

In Hansen’s simulations, moons that were moving away from their host planets would often rumble back, crashing into the planet and creating huge clouds of dust. These dust clouds glowed in the infrared, illuminated and heated by starlight. But it only lasted about 10,000 years before disappearing, which is the “blink of an eye” in cosmic calculations.

Hansen said observations from NASA’s Wide Field Infrared Space Telescope show that every star undergoes such an event at some point in its life.

Because these dust clouds are short-lived, astronomers have only observed about a dozen of them.

In addition, some astronomers remain unconvinced that these dust clouds originated from the exomoon and instead speculate that they may be the result of a collision between two planets.

In any case, more observations are needed to understand the role of exomoons in the evolution of exoplanets and to determine whether these collisions could affect alien life.

“The moons are often considered beneficial. They are believed to help stabilize the tilt of the planet’s axis, making the seasons more pleasant and more livable,” Hansen explained. However, a collision like the one in Hansen’s simulation would certainly outweigh this advantage, destroying any chance of life with a fiery explosion.

Source: Living Science