As Pluto embarks on its lengthy 248-year orbit, scientists have observed notable changes in its atmosphere, particularly as it transitions into colder and darker regions of the outer Solar System. This shift is expected to lead to a gradual thinning of its predominantly nitrogen atmosphere, which may ultimately freeze out over the coming decades.
Researchers from the Planetary Science Institute, led by Senior Scientist Amanda Sickafoose, have utilized starlight measurements to track this atmospheric thinning. Their findings indicate that Pluto’s atmospheric pressure has decreased by 16% from mid-2021 to July 2023. Prior to this period, atmospheric pressure remained stable at approximately 10 millibars, a value that is about 1/100,000 of Earth’s atmospheric pressure, with occasional fluctuations influenced by solar heating at the northern pole.
Tracking Atmospheric Changes through Occultations
Studying Pluto’s atmosphere poses significant challenges due to its distance from Earth. As Pluto approaches perihelion, it experiences increased solar heating, which causes variations in its atmosphere. While earlier models suggested that the atmosphere would completely freeze out at aphelion, recent observations indicate that some atmospheric components may persist throughout its orbit.
To monitor these changes, scientists have employed a technique known as occultations, which occur when Pluto passes in front of a more distant star. This event allows starlight to pass through Pluto’s atmosphere, where it can be absorbed or deflected by atmospheric particles. The degree of light absorption provides insights into the thickness and structure of the hazes present in the atmosphere.
Challenges and Observational Techniques
Observing Pluto’s occultations requires precise coordination among teams of scientists, as the planet’s shadow can span vast distances across Earth. By strategically positioning themselves along the predicted shadow paths, researchers can gather data on different regions of Pluto’s atmosphere. During these events, telescopes measure the brightness of the star before, during, and after the occultation, allowing scientists to calculate the density of the atmosphere.
Sickafoose expressed her astonishment at how the simple act of monitoring starlight can yield valuable information about Pluto’s thin atmosphere. “I’m constantly amazed at how the simple technique of watching starlight dim and reappear allows us to study a thin atmosphere – a few millionths of the Earth’s – on a world two-thirds the size of our Moon and 30 times farther from the Sun,” she stated.
Implications for Future Research
Despite the valuable data obtained from these occultation measurements, many questions remain regarding the future of Pluto’s atmosphere. The recent findings suggest a pressure plateau from the New Horizons flyby in 2015 until around 2021, followed by a significant pressure drop. The team noted variations in atmospheric pressure, with a decrease of 7 ± 6% at 1275 km and 16 ± 2% at 1215 km when haze is included.
As Pluto continues its journey farther from the Sun, further observations and analyses of the current occultation data will be essential to understand the evolving characteristics of its atmosphere.
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Original source: universetoday.com
