“An image of Pluto’s atmosphere, backlit by the sun, captured by the New Horizons spacecraft as it zipped past the planet.” Source of caption and photo: online version of the NYT article quoted and cited below.
(p. A13) Confounding expectations, Pluto’s atmosphere has actually thickened over the last 26 years, and many planetary scientists changed their minds. Maybe the atmosphere would persist throughout Pluto’s 248-year orbit, they speculated.
Now the story appears to be changing again. New Horizons obtained a snapshot of the structure of the atmosphere by looking at distortions in radio signals sent from Earth passing through Pluto’s atmosphere.
What the new measurement “seems to have detected is a potential for the first stages of that collapse just as New Horizons arrived,” Dr. Stern said. “It would be an amazing coincidence, but there are some on our team who would say, ‘I told you so.’ ”
Even if the atmosphere is collapsing, though, the view from the night side of Pluto is, at present, spectacularly hazy. A photograph showing a silhouette of Pluto surrounded by a ring of sunlight “almost brought tears” to the atmospheric scientists, Dr. Summers said, showing sunlight scattered by small particles of haze up to 100 miles above the surface.
“This is our first peek at weather in Pluto’s atmosphere,” he said.
Computer models had suggested that the haze would float within 20 miles of the surface, where temperatures are about minus 390 degrees Fahrenheit. Instead, the haze particles formed higher, 30 to 50 miles up, where temperatures are balmier, around minus 270.
“We’re having to start from scratch to understand what we thought we knew about the atmosphere,” Dr. Summers said.
For the full story, see:
KENNETH CHANG. “Pluto’s Atmosphere Is Thinner Than Expected, but Still Looks Hazy.” The New York Times (Sat., JULY 25, 2015): A13.
(Note: ellipses added.)
(Note: the online version of the article has the date JULY 24, 2015.)