As if being downgraded to dwarf planet status was not enough, Pluto may now be in danger of losing its wispy atmosphere by 2030. The dire prediction comes from a 28-year study of the small celestial body, which lies at the edge of our solar system, by a team of international researchers led by University of Tasmania astronomer Andrew Cole.
Located 3.7 billion miles (5.9 billion kilometers) from the Sun, Pluto is one of the most mysterious and intriguing celestial objects in our solar system. While the dwarf planet was discovered in 1930, it was not until 1980 that astronomers began to suspect it may have an atmosphere. The suspicion was confirmed in 1989, during Pluto's last closest flyby of the Sun, when researchers detected a delicate layer of gases surrounding the planet. It largely comprised nitrogen with traces of methane and carbon monoxide, all of which had vaporized from their solid icy forms on its surface.
Since then, scientists have been trying to find out more about the ebbs and flows of the distant planet's atmosphere with the help of ground-based observations of stellar occultations. The phenomena are similar to eclipses and occurs when a minor planet (Pluto, in this case) passes in front of a faint, distant star. Observations of Pluto as it passes in front of the object, causing it to "disappear" for a few minutes, allow scientists to track changes in its temperature and atmospheric pressure. Fortunately for astronomers, during the last decades of the 20th century and the first decades of the 21st century, the Earth and Pluto were perfectly aligned with a dense cluster of stars in the center of the Milky Way. This provided scientists numerous opportunities to capture data on the dwarf planet's atmosphere and radius.
The information collected, along with images captured by NASA's New Horizons spacecraft during its July 2015 flyby of the planet, allowed researchers to determine that similar to Earth, Pluto's axis is tilted on its side. This means that as it revolves around the sun, first the north, and then the south pole, is inclined toward the distant star, allowing for four distinct seasons. However, given that it takes the dwarf planet 248 earth years to complete a single orbit around the Sun, each season lasts for about 60 years! To make matters worse, Pluto has an extremely elliptical orbit, with its distance from the Sun varying from 2.7 to 4.6 billion miles (4.4 to 7.4 billion kilometers). This means that at its furthest distance, the celestial body receives no sunlight at all.
“We were able to construct seasonal models of Pluto and how it responds to changes with the amount of sunlight it receives as it orbits the Sun,” Dr. Cole said. “What we found was when Pluto is farthest away from the Sun, and during its winter in the northern hemisphere, nitrogen freezes out of the atmosphere.”
Following Pluto's most recent closest approach to the Sun in 1989, the tiny planet has been steadily moving away from the star. The trend, expected to continue till the year 2113, will eliminate even the weak sunlight that has kept Pluto's atmospheric nitrogen in gaseous form. As the icy planet, which sports an average temperature of -356 degrees Fahrenheit (-215 degrees Celsius), plunges into an extended northern autumn and winter, the astronomers expect its nitrogen-laden atmosphere to freeze and collapse.
“The atmospheric pressure has tripled over the past three decades, but as the dwarf planet orbits, our modeling showed that most of the atmosphere would condense out to almost nothing left,” Dr. Cole said in a statement. “What our predictions show is that by 2030 the atmosphere is going to frost out and vanish around the whole planet." The researcher adds, "If it does freeze over, Pluto may appear brighter in the sky due to sunlight reflecting."
Though being able to see Pluto more distinctly is a positive for Earthlings, the scientists, who published their findings in the journal Astronomy and Astrophysics on March 6, 2019, believe the frozen nitrogen frost covering Pluto will make it harder for future spacecrafts to capture clear images of the planet. “The striking red terrain seen in the New Horizons images could fade away if they are snowed under with nitrogen frost,” Dr. Cole said. "This research has been crucial in furthering our understanding of Pluto and testing what we know about atmospheres, ices, and climate at extreme conditions.”
On a more positive note, a recent informal poll taken by a small group of scientists voted overwhelmingly in favor of reinstating Pluto's full planetary status. Hopefully, they will be able to convince researchers worldwide to agree and allow the distant, frigid body to reclaim its rightful place as the ninth planet of our solar system.
Resources: CNN.com, phys.org, airandspace.si.edu, techexplorist.com