First view of Mars with the Webb Telescope


The brand new James Webb Space Telescope captured its first images and spectra of Mars on September 5, 2022, a unique perspective of the red planet with its infrared sensitivity.

Webb’s unique observation post, almost 1.5 million kilometers away at the Sun-Earth Lagrange Point 2 (L2), offers a view of the observable disk of Mars (the part of the sunlit side facing towards the telescope).

As a result, Webb can capture images and spectra with the spectral resolution necessary to study short-term phenomena such as dust storms, weather patterns, seasonal changes and, in a single observation, processes that occur at different times (during the day, sunset and night) of a Martian day.

Because it is so close, the Red Planet is one of the brightest objects in the night sky in terms of visible light (that human eyes can see) and the infrared light that Webb is designed to detect. This poses special challenges for the observatory, which was built to detect the extremely faint light from the most distant galaxies in the universe.

Webb’s instruments are so sensitive that, without special observing techniques, the bright infrared light from Mars is blinding, causing a phenomenon known as “detector saturation.” The astronomers adjusted for the extreme brightness of Mars using very short exposures, measuring only part of the light that hit the detectors and applying special data analysis techniques.

Webb’s first images of Mars, captured by the near-infrared camera (NIRCam), show a region of the planet’s eastern hemisphere in two different wavelengths, or colors, of infrared light. This image shows a NASA surface reference map and the Mars Orbiter Laser Altimeter (MOLA) on the left, with the two fields of view from the Webb NIRCam instrument superimposed. Near-infrared images of Webb are shown to the right.

Webb’s first near-infrared spectrum of Mars, captured by the Near-Infrared Spectrograph (NIRSpec), demonstrates Webb’s power to study the Red Planet with spectroscopy, ESA reports in a statement.

While images of Mars show built-in differences in brightness over a large number of wavelengths from place to place across the planet on a particular day and time, the spectrum shows the subtle variations in brightness between hundreds of different wavelengths. wavelengths representative of the planet as a whole. Astronomers will analyze the features of the spectrum to gather additional information about the planet’s surface and atmosphere.

In the future, Webb will use these imaging and spectroscopic data to explore regional differences across the planet and look for trace species in the atmosphere, including methane and hydrogen chloride.

These observations of Mars were made as part of Webb’s Cycle 1 Guaranteed Time Observing (GTO) Solar System program, led by Heidi Hammel of the Association of Universities for Research in Astronomy (AURA).

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