Pluto Hasn’t Always Been a Small Ice Planet
Before NASA’s New Horizons probe flew past Pluto in July 2015, some scientists speculated that it would probably see an icy, cratered ball on the outskirts of the solar system.
How wrong they were.
Not only is Pluto a dynamic world with icy plains, huge ice mountains and a hazy atmosphere, it also may have once had liquid nitrogen on its surface, according to new models developed by the New Horizons team.
In the most extreme circumstances of this simple climate model, which was developed using data from New Horizons, “the pressure and temperature are high enough that liquids may have existed on the surface of Pluto, liquid nitrogen, in the past,” New Horizons principal investigator Alan Stern said during a press conference Monday.
“Pluto’s atmospheric pressure has varied dramatically over millions and in fact billions of years, increasing in some instances perhaps by as much as a factor of four orders of magnitude.”
Today, the dwarf planet is too cold for any liquid nitrogen to exist.
However, due to the variations in Pluto’s orbit, it’s possible that at some point in the world’s geological past, it may have harbored enough atmospheric pressure to increase the planet’s average temperature by an amount that would have supported liquid nitrogen on its surface.
An extreme season with higher atmospheric pressure and warmer weather could have occurred when Pluto was at its closest point to the sun and its poles were pointed toward the star within the last million years, New Horizons team member Rick Binzel said during the press conference.
The world may have gone through other warmer cycles in the past as well, and it may yet head toward another warm cycle in the future.
At the moment, Pluto may be in the intermediate stage between two extremes of its cycle.
“We find that Pluto’s atmospheric pressure today is atypically low, and that in the past, it can have been as much as 1,000 to 10,000 times higher,” Stern said.
“Currently Pluto’s atmospheric pressure is measured at 10 microbars, [which was] measured by New Horizons during the flyby, that’s 1/100,000th of the pressure at sea level on the Earth.”
Now, don’t get too excited about possible nitrogen-bathing aliens.
The results from this modeling don’t necessarily mean that Pluto once could have supported life, but it does mean that scientists are closer to understanding some of the geological features on the world that may have been carved by liquid nitrogen.
“These simple models tell us that there is a lot more work ahead,” Stern said.
“They may also explain some of the features on the surface that we are seeing in high resolution imagery from New Horizons.”
For example, a 20-mile-long feature looks somewhat like a frozen-over lake, Stern said, and there are branched features seen by the probe that seem as though they may have been formed by liquid.
Frozen nitrogen already flows in the form of glaciers on Pluto, in the world’s informally named Sputnik Planum region. This area is located in the heart-shaped feature on the dwarf planet’s surface.
Scientists will continue to learn more about Pluto as New Horizons continues its journey deep into the solar system.
The probe is still beaming back the data it collected during the close pass of Pluto and will continue to do so for months to come.