The first images of the planet Mars captured by the James Webb Space Telescope. What NASA discovered with its help?

Credit image: NASA/ESA/CSA/STScI
Credit image: NASA/ESA/CSA/STScI

Article by: Andacs Robert Eugen, on 20 September 2022, at 10:52 am Los Angeles time

NASA's James Webb Space Telescope captured the first images and spectra of Mars.

It provided a unique perspective of our neighboring planet with the help of its infrared features, thus complementing the data gathered by other devices.

From there, Webb provided a view of Mars' observable disk (the portion of the sunlit side facing the telescope) and can capture images and spectra with the resolution needed to study short-term phenomena such as dust storms, weather patterns, seasonal changes, and processes that occur at different times of a Martian day.

Credit image: NASA/ESA/CSA/STScI
Credit image: NASA/ESA/CSA/STScI

How the Webb telescope manages to withstand the glare of Mars?

Because it is so close to Earth, the Red Planet is one of the brightest objects in the night sky, both in light visible to the human eye and in the infrared light that Webb is designed to detect it.

This poses special challenges for the telescope, which was built to detect the extremely faint light of the most distant galaxies in the universe. Webb is so sensitive that without special observing techniques, the bright infrared light from Mars is blinding, causing a phenomenon known as "detector saturation." 

Astronomers adjusted for the extreme brightness of Mars by measuring only a fraction of the light that hit the detectors, using very short exposures and applying special data analysis techniques. 

What does Webb's first images of Mars show?

Webb's first images of Mars, captured 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 longer-wavelength NIRCam image shows thermal emission - the light emitted by the planet as it loses heat. 

Luminosity is related to surface and atmospheric temperature. The brightest region on the planet is where the Sun is almost overhead because it is generally the warmest. Brightness decreases toward the polar regions, which receive less sunlight, and less light is emitted from the colder northern hemisphere, which experiences winter at this time of year. 

Why the Hellas Basin on Mars appears darker than its surroundings?

But temperature isn't the only factor that affects the amount of light reaching Webb with this filter. As the light emitted by the planet passes through the Martian atmosphere, some are absorbed by carbon dioxide molecules. The Hellas Basin, the largest and best-preserved impact structure on Mars, spanning more than 2,000 kilometers, appears darker than its surroundings because of this effect. 

A team from NASA's Goddard Space Flight Center has released the first near-infrared spectrum for Mars, and preliminary analyzes of the spectrum show a rich set of spectral features that contain information about dust, ice clouds, what kind of rocks are on the surface of the planet and the composition of the atmosphere. 

The spectral signatures-including deep valleys known as absorption features of water, carbon dioxide, and carbon monoxide are easy to detect with Webb. 

In the future, the team will use this data to explore regional differences on the planet and look for traces of gases in the atmosphere, including methane and hydrogen chloride.

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