Mars Is Mighty: First Webb Space Telescope Images of Red Planet



The first pictures and spectra of Mars were taken by NASA's James Webb Space Telescope on September 5. The robust telescope complements the information being gathered by orbiters, rovers, and other telescopes by offering a distinctive perspective on our neighboring planet through its infrared sensitivity. Webb is a global partnership between the Canadian Space Agency and the European Space Agency (Canadian Space Agency).

Nearly a million miles beyond Earth, at the Sun-Earth Lagrange point 2, sits Webb's special observation station (L2). Views of Mars' visible disk are provided (the portion of the sunlit side that is facing the telescope). Because of this, Webb is able to take photos and spectra with the spectral resolution required to investigate short-lived phenomena like dust storms, weather patterns, seasonal changes, and, in a single observation, processes that happen at different times of the day (day, sunset, and night) on Mars.

The Red Planet is one of the brightest objects in the night sky, both in terms of visible light (which human eyes can perceive) and the infrared light that Webb is meant to detect, due to its close proximity to Earth. The observatory has particular difficulties because it was designed to pick up the incredibly faint light from the universe's most distant galaxies. In fact, the strong infrared light from Mars is so blinding without particular viewing methods, leading to a phenomena known as "detector saturation," because Webb's equipment are so sensitive. By detecting only a portion of the light that reached the detectors, using extremely brief exposures, and utilizing specialized data analysis methods, astronomers were able to compensate for Mars' high brightness.

The second Sun-Earth Lagrange point (L2), which is situated roughly 1.5 million kilometers (1 million miles) from Earth on the opposite side of the Sun, is where Webb orbits the Sun. While Webb orbits the Sun, it is not precisely placed at L2 and instead travels in a halo orbit around L2. With this orbit, Webb can keep its position in relation to Earth while simultaneously keeping a safe distance from the Sun, Earth, and Moon's intense lights. Source: STScI

The Near-Infrared Camera (NIRCam) on Webb's spacecraft took the top image on this page, which depicts a portion of Mars' eastern hemisphere at two different infrared light wavelengths. In this image, the two Webb NIRCam instrument field of views are superimposed over a NASA surface reference map on the left and the Mars Orbiter Laser Altimeter (MOLA) on the right. The photographs on the right are from Webb's near-infrared camera.

Reflected sunlight dominates the NIRCam's shorter-wavelength (2.1 microns) image [top right], which displays surface details comparable to those shown in images taken in visible light [left]. This image clearly shows the Huygens Crater rings, Syrtis Major's dark volcanic rock, and the Hellas Basin's brightening.

The lower right-hand corner of the NIRCam image at a longer wavelength (4.3 microns) displays thermal emission—light that the planet emits as it loses heat. The temperature of the surface and the environment affects the brightness of 4.3-micron light. Because it is typically the warmest, the area of the planet closest to the Sun is also the brightest. Less light is emitted from the northern hemisphere, which is cooler and currently experiencing winter, and brightness diminishes toward the polar regions, which receive less sunshine.

However, the amount of 4.3-micron light that passes through this filter and reaches Webb is not only influenced by temperature. Some of the planet's light that strikes Mars is absorbed by carbon dioxide (CO2) molecules as it travels through the planet's atmosphere. This effect makes the Hellas Basin, which spans more than 1,200 miles (2,000 kilometers) and is the biggest well-preserved impact formation on Mars, appear darker than its surroundings.

The primary investigator of these Webb findings, Geronimo Villanueva of NASA's Goddard Space Flight Center, said, "This is actually not a thermal effect at Hellas. Because of its lower altitude, the Hellas Basin has higher air pressure. Due to a phenomenon known as pressure widening, the higher pressure causes the thermal emission at this specific wavelength range [4.1-4.4 microns] to be suppressed. To separate these opposing effects in these data will be quite intriguing.

Additionally, Villanueva and his group made available Webb's first near-infrared spectrum of Mars, showcasing the capability of Webb to investigate the Red Planet through spectroscopy.
On September 5, 2022, as part of the Guaranteed Time Observation Program 1415, Webb's Near-Infrared Spectrograph (NIRSpec) observed Mars and recorded its first near-infrared spectra (G140H, G235H, G395H). Thermal emission at longer wavelengths and reflected sunlight at shorter wavelengths dominate the spectrum. According to preliminary study, the wavelengths where light is absorbed by molecules in Mars' atmosphere, notably carbon dioxide, carbon monoxide, and water, are where the spectral dips appear. Other details provide information on the surface characteristics, clouds, and dust. It is possible to determine the abundances of specific chemicals in the atmosphere by creating a best-fit model of the spectrum, for instance, using the Planetary Spectrum Generator. Credit: Mars JWST/GTO team, NASA, ESA, CSA, STScI

The spectrum displays the subtle variations in brightness between hundreds of different wavelengths that are representative of the planet as a whole, as opposed to the images, which show differences in brightness integrated over a large number of wavelengths from place to place across the planet at a specific day and time. To learn more about the surface and atmosphere of the planet, astronomers will examine the spectrum's characteristics.

This infrared spectrum was created by combining measurements from Webb's Near-Infrared Spectrograph's six high-resolution spectroscopic modes (NIRSpec). A preliminary investigation of the spectrum reveals a wealth of spectral signatures that provide details about the atmosphere, icy clouds, types of rocks on the planet's surface, and dust. With Webb, it is simple to identify the spectral signatures of water, carbon dioxide, and carbon monoxide, which include deep troughs known as absorption characteristics. The scientists are getting ready to submit an article to a scholarly journal for peer review and publication after examining the spectral data from these observations.

The Mars team will later use these images and spectroscopic data to investigate regional variations on the planet and look for trace gases like methane and hydrogen chloride that may be present in the atmosphere.                                        
By MARGARET CARRUTHERS, SPACE TELESCOPE SCIENCE INSTITUTE 


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