Mars (Near-Infrared Spectrum)

Editor’s Note: The findings reported here are based on preliminary results that have not been shared formally with the scientific community via peer-reviewed publication.

Webb’s first near-infrared spectrum of Mars, captured by the Near-Infrared Spectrograph (NIRSpec) on September 5, 2022, reveals chemical and physical properties of Mars’ surface and atmosphere. Data are shown in white, with a best-fit model in purple. 

The spectrum shows a combination of sunlight reflected from Mars’ surface and atmosphere, and light emitted by the planet as it gives off heat. Wavelengths between 1 and 3 microns are dominated by reflected light, while those between 3 and 5 microns are dominated by emitted light. Both the reflected and emitted light pass through Mars’ atmosphere, affecting the brightness of various wavelengths and the shape of the spectrum in various ways.

The deep valleys are absorption features caused when specific wavelengths are blocked by gases such as carbon dioxide, water, and carbon monoxide. Other details, like the broad shape of the spectrum and the slope of the curve at different points, reveal information about dust, clouds, and surface features. 

The data were collected using six different high-resolution spectroscopy modes (grating modes), each of which covers a different wavelength range. (The white line is not continuous because there are small gaps in coverage.) The best-fit model takes into account the data as well as other known properties of Mars. Constructing a best-fit model using a tool such as the Planetary Spectrum Generator makes it possible to estimate abundances of given molecules in the atmosphere.

NIRSpec was built for the European Space Agency (ESA) by a consortium of European companies led by Airbus Defence and Space (ADS) with NASA’s Goddard Space Flight Centre providing its detector and micro-shutter subsystems.

See the Fast Facts below for additional technical details. 

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