Scientists designed the James Webb Space Telescope to be able to detect faint light from distant parts of the universe. But with a few careful adjustments, the high-tech telescope was recently able to turn its attention toward a much closer and brighter object in the night sky: Mars.
The telescope captured its first images and spectra of the Red Planet on September 5, according to NASA, which is collaborating with scientists at the European Space Agency (ESA) and Canadian Space Agency (CSA) on the James Webb project.
Webb, which launched in December 2021 and is located roughly one million miles away from Earth (1.6 million kilometers), was able to capture the sunlit side of the Red Planet that was facing the telescope. From its vantage point, Webb can at once observe Martian processes that occur at various times of day, and it will help researchers study short-term phenomena like seasonal changes, weather and dust storms, per NASA. Webb’s images provide insights that help complement data gathered by the other telescopes, rovers and orbiters that are studying Mars.
Because Mars is so close and so bright—and because Webb is so sensitive—researchers had to employ special observing techniques to avoid what’s known as detector saturation, a phenomenon caused by too much infrared light that ‘blinds’ the sensors. To get around this issue, scientists used very short exposures and only measured some of the light that reached Webb’s instruments.
“The fact that, when we opened the images and when we got the spectra, we actually could get the data and they were good data, it was exciting,” says Sara Faggi, an astrophysicist working on the project for NASA, to New Scientist’s Alex Wilkins.
The telescope’s first images of Mars, captured using its Near-Infrared Camera (NIRCam) at two different wavelengths, show an area of the planet’s eastern hemisphere. The images depict surface features such as dust layers, craters and dark spots, including the Hellas Basin, Syrtis Major and Huygens Crater. They also show variations in temperature at different latitudes and times of day, revealing warm regions where the Sun was almost directly overhead, as well as cooler areas in the northern hemisphere and near Mars’ polar regions.
Webb also captured its first near-infrared spectrum of Mars, which shows “the subtle variations in brightness between hundreds of different wavelengths representative of the planet as a whole,” per NASA. The spectrum, created using data from all six high-resolution spectroscopy modes of the telescope’s Near-Infrared Spectrograph (NIRSpec), provides astronomers with information about Mars’ icy clouds, dust, surface rocks and atmospheric composition.
The telescope may also be able to help astronomers look for trace gases in the Martian atmosphere, including hydrogen chloride, methane and other chemical compounds. The presence of methane, a potential marker of life in Mars’s past, has been particularly tricky to confirm using other instruments. Now, scientists are hopeful that Webb will be able to help.
“The big conundrum has been that the rovers on the surface and the observational data have left a gap between zero and 10 kilometers,” Giuliano Liuzzi, an atmospheric spectroscopist and the lead investigator on the project, said at a press conference, as reported by Space.com’s Robert Lea. “Now we have James Webb, we can see the full column [of the atmosphere] all the way to the surface where the rover is. So, we've provided a new way to solve this conundrum.”