It was a cloudy day on Titan.
It was clear on the morning of Nov. 5 when Sébastien Rodriguez, an astronomer at Paris Cité University, downloaded the first images of Saturn’s largest moon taken by NASA’s James Webb Space Telescope. He saw what looked like a large cloud near Kraken Mare, a sea 300 meters deep in the north polar region of Titan.
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“What a wake up call this morning,” he said in an email to his team. “I think we see a cloud!”
This sparked a weather emergency of sorts among the Al Rokers of the cosmos, sending them scrambling for more cover.
Titan has long been a gem of curiosities for astronomers. Less than half the size of Earth, it has its own atmosphere thick with methane and nitrogen – and even denser than the air we breathe. When it rains on Titan, it rains gasoline; when it snows, the snowdrifts are black as coffee grounds. Its lakes and streams abound in liquid methane and ethane. Beneath its frozen mud crust hides an ocean of water and ammonia.
Aspiring astrobiologists have long wondered if the chemistry that prevailed during Earth’s early years was being recreated in the muddy mounds of Titan. Potential precursors to life make the smoggy world (where the surface temperature is minus 290 degrees Fahrenheit) a long-held hope for the discovery of extraterrestrial chemistry.
To that end, missions are planned on Titan, including sending a nuclear-powered drone named Dragonfly to hop around Saturn’s moon by 2034 as well as more theoretical trips like sending a sub sailor to explore his oceans.
In the meantime, however, despite observations from Voyager 1 in 1980 and the Cassini Saturn orbiter and its Huygens lander in 2004-2005, planetary scientists’ models of Titan’s atmospheric dynamics were still only tentative. But the Webb Telescope, which launched nearly a year ago, has infrared eyes that can see through Titan’s haze.
So when Conor Nixon of NASA’s Goddard Space Flight Center received Rodriquez’s email, he was excited.
“We had waited years to use Webb’s infrared vision to study Titan’s atmosphere,” Nixon said. “Titan’s atmosphere is incredibly interesting, not only because of its methane clouds and storms, but also because of what it can tell us about Titan’s past and future, including if it ever had an atmosphere.”
Nixon contacted two astronomers the same day – Imke de Pater of the University of California, Berkeley and Katherine de Kleer of the California Institute of Technology – who were affiliated with the twin 10-meter Keck telescopes on Mauna Kea in Hawaii and discussed called the team Keck Titan. He called for immediate follow-up observations to see if the clouds were changing and which way the winds were blowing.
As de Pater explained, such last-minute requests aren’t always possible, because telescope time is a precious commodity.
“We were extremely lucky,” she said.
The duty observer that night, Carl Schmidt of Boston University, was one of their collaborators on other planetary studies.
Keck staff, de Pater added, are also keen to support Webb Telescope observations.
“They love solar system objects,” she said, “because they’re just neat and always changing over time.”
With visible light images from Keck and infrared images from the Webb Telescope, Nixon and his colleagues were able to probe Titan from ground features through the various layers of its atmosphere – everything a long-range meteorologist could need. .
And more is on the way.
In an email, Nixon said his team is especially eager to see what happens in 2025, when Titan reaches its northern autumnal equinox.
“Shortly after the last equinox we saw a giant storm on Titan, so we’re excited to see if the same thing will happen again,” he said.
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