It’s been a cloudy season for Saturn’s largest moon, Titan.
Titan is an strange world, resembling Earth if the land was made of water ice, rivers and seas were filled with liquid methane and other hydrocarbons, and the atmosphere was thick and hazy, dotted with methane clouds. According to a NASA statement, the James Webb Space Telescope (Webb or JWST) has now observed two of those clouds during observations on November 4 that have thrilled scientists.
“Fantastic! Love seeing the cloud and the obvious albedo markings,” Heidi Hammel, a planetary scientist at the Association of Universities for Research in Astronomy and a project lead for JWST’s solar system work, wrote in an email shared in the statement, referring to glimpses of bright and dark regions of Titan’s surface.
Conor Nixon, an astronomer at NASA’s Goddard Space Flight Center in Maryland, arranged for JWST to study Titan for a total of 15 hours during its first year. Nixon’s team, in particular, wants to explore Titan’s atmosphere, with the goal of mapping the distribution of haze and identifying new gases, among other goals.
And the scientists were thrilled at the data JWST sent them. “At first glance, it is simply extraordinary,” Sebastien Rodriguez, an astronomer at the Université Paris Cité and colleague on the research, wrote in an email shared in the statement. “I think we’re seeing a cloud!”
As they combed through the data, the researchers discovered not one, but two clouds, one of which was intriguingly located over Kraken Mare, Titan’s largest sea. The scientists were soon inspired to find a way to revisit those clouds in order to better understand how they changed over time. The team contacted the Keck Observatory in Hawaii, which was able to obtain Titan observations just two days after JWST.
“We were concerned that the clouds would be gone when we looked at Titan two days later with Keck,” Imke de Pater, an astronomer at the University of California, Berkeley, who leads Keck’s observations of Titan, said in the statement. “But to our delight there were clouds at the same positions, looking like they had changed in shape.”
That alignment, however, does not necessarily imply that Keck saw the same clouds as JWST. Scientists expected high cloud activity because Titan’s northern hemisphere is in late summer and absorbing more solar radiation, so Keck’s clouds could have formed recently.
And the scientists aren’t done with the data yet. The clouds were identified in images taken by JWST’s Near-Infrared Camera (NIRCam), a powerful camera that can image a target in several different wavelengths of light, allowing scientists to separate out Titan’s lower atmosphere.
However, the researchers haven’t even finished analyzing all of the data from NIRCam, and a second instrument was also in use. Spectra were collected using the observatory’s Near-Infrared Spectrograph (NIRSpec). This technique divides light reflected off surfaces such as Titan’s atmosphere and measures how much of each wavelength is present. The spectra should help scientists figure out what compounds are in the lower atmosphere, including a strange bright spot near the moon’s south pole.
According to the statement, JWST will return to Titan in May or June 2023, this time using its Mid-Infrared Instrument (MIRI), which will improve scientists’ understanding of the chemicals in the moon’s strange, hazy atmosphere.
Titan observations are especially important now, during a quiet period in spacecraft visits to the icy moon. Cassini, NASA’s spacecraft, arrived at Saturn in 2004 and flew past the moon more than a hundred times before it was destroyed in 2017. And NASA is working on a new Titan mission called Dragonfly, which will send a drone through the hazy skies, allowing scientists to study the moon from a variety of vantage points.
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