JWST Observes Mars Very Carefully

JWST captured a pair of infrared images of Mars taken at two different wavelengths that reveal thermal features due to sunlight.

Beth Johnson

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IMAGE: First Webb observations of Mars. CREDIT: NASA, ESA, CSA, STSci, MARS JWST/GTO team

If it feels like we’re getting a lot of “JWST does something for the first time” stories this year… it’s because we are. That’s by design for a couple of reasons. One, obviously, is to get the public excited about the capabilities of a telescope that went into massive cost overruns. Two is to get science data into the hands of early observers who can then learn the instrumentation and nuances of gathering data with the big infrared light bucket.

This week, the newest images are of Mars. Once again, they have tracked JWST to look inside our solar system, just as they did with Jupiter last month. These observations aren’t exactly simple to take, either. Mars is incredibly close to the telescope, making it a very bright object both in visible and infrared light. Since JWST is a giant light bucket, astronomers had to use some special techniques to not cause “detector saturation” while collecting data. They took the images in very short exposures, only measuring part of the light hitting the detectors, and then applied some bespoke data analysis methods to reduce that data.

And what they managed to capture was a portion of Mars’s eastern hemisphere in two different infrared wavelengths. Two images have been released along with a reference map collected by NASA and the Mars Orbiter Laser Altimeter. The smaller, more orange image is dominated by reflected sunlight collected at 2.1 microns and matches up to the visible-light version. The longer wavelength version — collected at 4.3 microns — is a product of the planet’s thermal emission or heat. That image shows which regions of the red planet were receiving the most sunlight at the time of the observation. You can see the images in our show notes at DailySpace.org.

IMAGE: This is Webb’s first near-infrared spectrum of Mars, demonstrating Webb’s power to study the Red Planet with spectroscopy. This near-infrared spectrum of Mars was captured by the Near-Infrared Spectrograph (NIRSpec) on 5 September 2022, over 3 slit gratings (G140H, G235H, G395H). The spectrum is dominated by reflected sunlight at wavelengths shorter than 3 microns and thermal emission at longer wavelengths. CREDIT: NASA/ESA/CSA/STScI and Mars JWST/GTO team

In addition to the infrared images, JWST also collected a near-infrared spectrum of Mars. While that spectrum is still being analyzed, the initial release shows the presence of carbon dioxide, carbon…

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Beth Johnson

Planetary scientist, podcast host. Communication specialist for SETI Institute and Planetary Science Institute. Buy me a coffee: https://ko-fi.com/planetarypan