Written by Margaret W. Carothers, Space Telescope Science Institute
NASA’s James Webb Space Telescope captured its first images and spectra of Mars on September 5. The telescope, an international collaboration with the European Space Agency (ESA) and the Canadian Space Agency (CSA), provides a unique perspective of infrared sensitivity on our neighboring planet. , to complement data collected by orbiters, rovers, and other telescopes.
Webb’s unique observation point, about a million miles from the Sun’s Lagrange Point 2 (L2), provides a view of Mars’ visible disk (the part of the sunlit side facing the telescope). As a result, Webb can capture images and files spectra With the spectral resolution needed to study short-term phenomena such as dust storms, weather patterns, seasonal variations, and, on a single note, processes occurring at different times (day, sunset, and night) of a Martian day.
Due to its close proximity to the Red Planet, the Red Planet is one of the brightest objects in the night sky in terms of visible light that the human eye can see and infrared light that Webb designed to detect. This poses special challenges for the observatory, which is built to detect the very faint light of the most distant galaxies in the universe. Webb’s instruments are so sensitive that without special observing techniques, the bright infrared light coming from Mars would lead to blindness, causing a phenomenon known as “detector saturation.” Astronomers have modified Mars’ extreme brightness using very short exposures, measuring only some of the light hitting detectors, and applying special techniques to analyze the data.
Webb’s first images of Mars, taken by the Near Infrared Camera (NIRCam), show a region of the planet’s eastern hemisphere at two different wavelengths, or colors of infrared light. The first image in this article shows a surface reference map from NASA and the Mars Orbiter Laser Altimeter (MOLA) on the left, with the Webb NIRCam field-of-view overlay. Webb’s near-infrared images are shown on the right.
The shorter wavelength NIRCam image (2.1 μm) [top right] It is dominated by reflected sunlight, thus revealing surface details similar to those seen in visible light images [left]. The Huygens Crater rings, dark igneous rocks in Syrtis Major, and brightness in the Hellas Basin are visible in this image.
The image with the longest wavelength NIRCam (4.3 μm) [lower right] Offers heat emissionThe light emitted by the planet as it loses heat. The brightness of the light of 4.3 microns is related to the temperature of the surface and the atmosphere. The brightest region on the planet is the region where the Sun is approximately, because it is generally the warmest. Brightness decreases toward the polar regions, which receive less sunlight, and emit less light than the cooler Northern Hemisphere, which goes through winter at this time of year.
However, temperature is not the only factor affecting the amount of 4.3 micron light that reaches Webb using this filter. When light from the planet passes through the Martian atmosphere, carbon dioxide (CO .) is absorbed2) Molecules. The Hellas Basin – the largest well-preserved impact structure on Mars, extending more than 1,200 miles (2,000 km) – appears darker than the surrounding areas due to this impact.
“This is actually not a heat effect in Hellas,” explained principal investigator, Jeronimo Villanueva of NASA’s Goddard Space Flight Center, who designed these Webb observations. “The Hellas Basin is of lower altitude, and therefore is subjected to higher air pressure. This higher pressure suppresses thermal emission in this specific wavelength range. [4.1-4.4 microns] Because of an effect called pressure expansion. It would be interesting to separate these competing effects in this data.”
Villanueva and his team also released Webb’s first near-infrared spectrum of Mars, demonstrating Webb’s ability to study the Red Planet using spectroscopy.
While the images show differences in brightness combined over a large number of wavelengths from one place to another across the planet on a given day and time, the spectrum shows the subtle differences in brightness between hundreds of different wavelengths that represent the planet as a whole. Astronomers will analyze features of the spectrum to gather additional information about the planet’s surface and atmosphere.
This infrared spectrum was obtained by combining measurements from all six high-resolution spectroscopy modes of Webb’s Near-Infrared Spectrograph (NIRSpec). The initial analysis of the spectrum shows a rich set of spectral features that contain information about dust, ice clouds, the type of rocks on the planet’s surface, and the composition of the atmosphere. Spectral signals – including deep valleys known as absorption features – can easily be detected for water, carbon dioxide, and carbon monoxide using Webb. The researchers analyzed the spectral data from these observations and are preparing a paper that they will submit to a peer-reviewed scientific journal for publication.
In the future, the Mars team will use this imaging and Spectral data To explore regional differences across the planet, searching for trace gases in the atmosphere, including methane and hydrogen chloride.
NIRCam and NIRSpec observations of Mars were made as part of Webb’s Cycle 1 Guaranteed Time Observation (GTO) program for the Solar System led by AURA’s Heidi Hamill.
Presented by the Space Telescope Science Institute
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