14 DAY TRIAL // As it turns out, planets that orbit the same star don't just keep each other company. On the contrary, they can influence one another just enough to encourage or pull the plug on the emergence and evolution of extraterrestrial lifeforms.
In a report in NASA's Astrobiology Magazine, scientists explain that neighboring planets can make each other more or less life-friendly by altering one another's climate. This can happen when they sit close enough to interact gravitationally.
A well-known scenario
Mind you, astronomers have long been aware of the fact that two distinct celestial bodies can interact with each other when the distance between them is not all that great. In fact, they've known this simple fact since they got to work studying the Earth and the Moon.
Thus, our planet and its accompanying satellite have been interacting since forever. Long story short, it is the Moon's gravitational pull that is partly to blame for the rises and decreases of sea levels that we call tides.
Scientists say that, by causing and sustaining tides over the course of billions of years, the Moon has ever so slightly modified Earth's spin rate, its axial tilt and its orbit. In doing so, it has influenced our planet's climate and, consequently, the evolution of life.
Specifically, researchers argue that it was the Moon's gravitational pull that compelled our home planet to switch from a 6-hour rotation period and, consequently, a 6-hour day, to the 24-hour rotation period we set our clocks to in this day and age.
Besides, it is this natural satellite of ours that helps keep the planet's axial tilt at 23.44 degrees. Were Earth's axial tilt to have any other value, the seasons and Earth's overall temperature would be very different to what we are accustomed to.
The same rules apply in outer space
Specialists say that interactions like the ones between Earth and the moon can also happen in outer space. More precisely, they can occur between planets that orbit the same star and that sit close enough to one another for their gravities to influence each other.
Looking to reach a better understanding of how planets in tightly packed solar systems can alter each other's climate and ability to sustain life, astronomers ran computer simulations of potential interactions between celestial bodies in two distinct solar systems, i.e. Kepler-62 and Kepler-186.
These solar systems were chosen because previous investigations have shown that they each host planets located in their star's so-called habitable zone, i.e. the space region where water can form and remain liquid on a planetary surface.
Thus, the planets Kepler-62e and Kepler-62f in the solar system Kepler-62 both sit in their parent star's habitable zone. The same is true about Kepler-186f, a planet about the size of Earth, that sits in the habitable zone of the solar system Kepler-186.
The computer simulations carried out as part of this research project showed that, as suspected, tidal effects from neighboring planets can, in fact, alter a celestial body's rotation and axial tilt and, consequently, its climate and its ability to sustain life.
“The presence of liquid water on a planet’s surface depends on many different parameters, some of which are the orbital distance, the shape of the orbit, the direction of the rotation axis of the planet and the rotation period of the planet.”
“All these quantities are influenced by dynamics and in particular by tidal dynamics,” researcher Emeline Bolmont, now working with the University of Namur in Belgium, said in a statement.
So, does any of these planets host life?
As mentioned, Kepler-62e, Kepler-62f and Kepler-186f all sit in the habitable zone of their parent star. However, it looks like the chances that Kepler-62-e and Kepler-186f might be home to alien lifeforms are pretty much slim to none.
This is because Kepler-62e most likely has a very small axial tilt. As a result, chances are that it does not experience seasons. Evidence indicates that the same is true about Kepler-186f. Kepler-62f, on the other hand, might have seasons and even days about as long as the ones we are accustomed to.