Just like Hubble, the James-Webb Telescope is able to provide amazing images of the planets of the Solar System. Most recently, images of Titan – the mythical moon of Saturn – have been taken and they rival those taken on the ground with the instruments of the Keck Observatory in Hawaii.
All astronomers know that the atmosphere is not only a filter that only lets through certain wavelengths (X-ray astronomy can only be done in space, for example), but that it is also harmful to image quality due to its turbulence. This last defect can be overcome by using adaptive optics technology which corrects the degradation of the images up to a certain point, by deforming a mirror of a telescope with jacks in response to a sounding of the state of the atmosphere above the instrument by means of a laser beam.
Thus, on the ground in Hawaii, astronomers like Franck Marchis of Seti Institutemember ofUnistellarand especially the planetary scientist Imke de Pater (famous for his treatise on planetary sciences), from the University of California at Berkeley, have been able to observe for many years the volcanic activity of Io, one of the moons of Jupiter, using the instruments of the Keck observatory equipped for adaptive optics. Today, Imke de Pater and his colleague Katherine de Kleer, assistant professor of planetary sciences and astronomy at the California Institute of Technologyare also studying the surface of Titan with the Keck.
With their teams, they have just joined other planetary astronomers who are using the James-Webb (JWST) to also observe Titan in the infrared range, but from space. The JWST is almost on par with the Keck and it can even go a little further in the study of Titan because of the instruments it has.
It is therefore a set of international teams of planetary scientists, including the one dedicated to Titan with the JWST and which is led by Conor Nixon of Goddard Space Flight Center from NASA, who have just posted the photos obtained on November 4, 2022 with the JWST, while explaining in several press releases what they were already teaching them, by comparing them in particular to images taken with the Keck about two days later. late.
Titan, an early Earth in the freezer
Remember that Titan is the only moon in the Solar System with a dense atmosphere, composed essentially of 98.4% molecular nitrogen with a little methane. It is also the only planetary body other than Earth that currently has rivers, lakes and seas but composed of hydrocarbons, including methane and ethane, not water. Titan is considered to be a kind of primitive Earth in the freezer where some of the prebiotic reactions that led to life on Earth can possibly be observed, or even alien lifeforms themselves.
After the end of NASA’s Cassini mission and its ESA’s Huygens module that landed on the surface of Titanplanetary scientists have been waiting impatiently for years to be able to use Webb’s infrared vision to study Titan’s atmosphere, test weather models there, and the evolution of its gaseous composition, and finally to see through its thick haze and study the characteristics of its albedo (bright and dark spots) on the surface of Titan.
As one of the press releases explains, it was the Frenchman Sebastien Rodriguez, of the Institut de Physique du Globe de Paris, who gave the alert on the morning of November 5, 2022 when he was the first to see the images. of Titan taken with the JWST near infrared camera (NIRCam), images already showing what appeared to be a large luminous cloud visible in the northern hemisphere of Titan.
Planetary scientists expected this observation because Titan climate models inspired by those known to be built on Earth predict that clouds form easily in the mid-northern hemisphere in late summer on Titan, when its surface is heated by the Sun.
But would these clouds also evolve according to the predictions of these models?
Webb’s piercing gaze and the meteorology of Titan
It was to find out that Conor Nixon contacted Imke de Pater and Katherine de Kleer by sending them the following email: We just received our first images of Webb’s Titan taken last night. It’s very exciting ! There appears to be a large cloud over the northern polar region near Kraken Mare. We wonder if it would not be quickly possible to start observations with the Keck to follow its evolution? »
Imke de Pater remembers his reaction at that time: We were concerned that the clouds were disappearing when we watched Titan two days later with Keck, but to our delight there were clouds in the same positions, appearing to have changed shape. »
The astronomers then turned to colleagues who specialize in modeling Titan’s atmosphere, including Juan Lora of Yale University, who said in the NASA statement: ” I’m glad we see this, as we’re planning good cloud activity for this season! We cannot be sure that the clouds on November 4 and 6 are the same, but they confirm seasonal weather patterns. »
With another JWST instrument, a Near Infrared Spectrograph (NIRSpec), planetary scientists also have access to spectra that are blocked by the Earth’s atmosphere, allowing them to probe the composition of the Earth’s lower atmosphere and surface. Titan in a way even Cassini couldn’t.
« This is some of the most exciting data we’ve seen on Titan since the Cassini-Huygens mission ended in 2017, and some of the best we’ll get before NASA’s Dragonfly arrives in 2032.comments Elizabeth Turtle of Johns-Hopkins University, who is the principal investigator of the mission Dragonfly. The analysis should really help us learn a lot about Titan’s atmosphere and meteorology. »
Elizabeth Turtle of the Johns-Hopkins University (APL) Applied Physics Laboratory and chief scientist of Dragonfly details the mission with ambitious objectives. To obtain a fairly accurate French translation, click on the white rectangle at the bottom right. The English subtitles should then appear. Then click on the nut to the right of the rectangle, then on “Subtitles” and finally on “Translate automatically”. Choose “French”. © APL, YouTube