on August 24a vital tool on board the James Webb Space Telescope (JWST) experienced a glitch that prompted the mission team to take it offline. The problem occurred when the Mid-infrared instrument (MIRI) experienced increased friction in one of its wheels in Medium-Resolution Spectroscopy (MRS) mode. The mission team took MIRI offline while they tried to diagnose the problem, leaving the observatory to continue making observations in other modes.
This came shortly after Webb was hit by a large micrometeoroid in late May that caused damage to one of the primary mirror segments. Fortunately, the damage this caused has not affected the telescope’s performance, and the mission team announced earlier this month that they had returned MIRI to operation. With everything in green, Webb has refocused its infrared optics on the cosmos and captured breathtaking images. This includes a new image of Saturn’s largest moon, Titan, that recently appeared online.
The image has been processed and uploaded to Twitter by Michael Radke, a Ph.D. student studying planetary atmospheres using laboratory photochemistry experiments at Johns Hopkins University (JHU). According to Radke, the image was acquired between November 4 and 5, he doubled in scale and added red, green and blue to represent different wavelengths (R = 4.8 um, G = 2.1 um, B = 1.4 um). These values were based on the Cassini missions Visible and infrared mapping spectrometer (VIMS).
These colors appear to correspond to the absorption spectrum of carbon monoxide (green), methane (blue) and nitrogen (red), the gases that make up most of Titan’s atmosphere. Titan also appears to be illuminated from the top left corner of the image, giving the impression of a sunrise. Planetary scientist, author and space journalist Emily Lakdawalla suggested the source could be light reflected from Saturn’s atmosphere. This image also gives a glimpse of the types of scientific operations Webb will perform with Titan and other bodies in our solar system.
Its powerful instruments and near- and mid-infrared imaging capabilities will enable astronomers to study the chemical composition of atmospheres in detail. Titan is of particular interest because it is the only moon in our atmosphere with a substantial atmosphere – where the air pressure is about 50% greater than Earth’s. Like Earth, Titan’s atmosphere is composed primarily of nitrogen gas (94%), with hydrocarbons such as methane making up the second largest fraction (5.65%).
Titan is the only other body in the solar system with a precipitation and evaporation cycle. While Earth has a water cycle, Titan has a methane cycle, where methane forms clouds in the moon’s atmosphere, falls to the surface as rain and replenishes methane lakes. In addition, Titan’s atmosphere is rich in chemical processes in which hydrocarbons are broken down by solar radiation into their components (i.e. carbon, hydrogen, oxygen and nitrogen) and then form new molecules that seep and settle on the surface.
Titan’s atmosphere and surface also possess something that no body other than Earth possesses: a rich prebiotic environment and organic chemistry. For this reason, astrobiologists have suspected that Titan is one of the most promising places to look for extraterrestrial life. For these reasons, Webb needs his instruments in working order, especially MIRI and the Near infrared spectrograph (NIRSpec). These will obtain highly accurate spectra from Titan’s atmosphere to observe these molecules and processes at work.
These studies will build on previous efforts of the joint NASA-ESA Cassini-Huygens mission, which studied Saturn and its satellites from 2004 to 2017. Both the orbiter and lander thoroughly studied Titan’s atmosphere and made many profound discoveries. The more detailed information Webb will obtain will be used to study Titan’s seasonal cycles, leading to more detailed climate models. This will help pave the way for missions like NASA’s Dragonfly rotorcraft to launch for Titan in 2027 and arrive sometime in the 2030s.