JWST's first glimpse of Mars reveals the Red Planet in a new light

JWST’s first glimpse of Mars reveals the Red Planet in a new light

The James Webb Space Telescope has made incredible progress, looking further into space and time than any telescope that has come before it. But it also shows us the Universe closer to home… and now it turns its golden eye to Earth’s neighbor Mars.

The resulting images show Mars in a very different light – infrared, in fact – giving us information about the Red Planet that we couldn’t see with our own naked eyes.

Since heat lets out infrared light (what we call thermal radiation), much of this information relates to the temperature of Mars, but there is some other information that scientists will be able to use to better understand a planet like this one, but so different from ours.

And, of course, the view is spectacular.

It’s actually a bit difficult for JWST to imagine anything near home. It is the most powerful telescope ever launched into space, designed to be sensitive enough to detect extraordinarily faint light from the most distant objects in the Universe. Compared to these, Mars blazes like a furnace.

To avoid the oversaturation that would usually result from this brightness, scientists taking the observations and processing the data had to employ techniques to compensate. The timing of the exposures was incredibly short and the data analysis was adjusted accordingly.

On the left, a simulated Mars globe shows features visible to JWST: top right, the 2.1 micron image shows surface features such as craters and dust. Bottom right, the 4.3-micron image shows a heat map of Mars’ atmosphere, warmed by the Sun. (NASA, ESA, CSA, STScI, Mars JWST/GTO team)

The result was worth it: a map of the side of Mars seen by the telescope in two wavelengths of infrared light. At 2.1 microns, the image is dominated by sunlight reflecting off the surface of Mars, so what we see is very similar to what we might see in optical wavelengths.

At 4.3 microns, the image is dominated by thermal radiation from the Martian atmosphere, brightest where the Sun is almost directly aligned with the planet. This is usually where the planet’s atmosphere is the hottest.

But heat is not the only source of infrared light at this wavelength. A dark smear can be seen down to the right of the brightest region in this wavelength; this is actually produced by a feature on the surface of Mars. It’s a huge impact basin called Hellas Planitia – it’s one of the largest craters on Mars and the entire solar system.

The atmosphere on Mars is 96% carbon dioxide, which absorbs light. And the atmosphere is thick enough above Hellas Planitia that this has an observable effect in infrared wavelengths.

jwst's mars spectrum showing signatures of elements of the martian atmosphere
The spectrum obtained by JWST, showing the chemical fingerprints of CO, CO2 and H20. (NASA, ESA, CSA, STScI, Mars JWST/GTO team)

“It’s actually not a thermal effect in Hellas,” says astronomer Geronimo Villanueva of NASA’s Goddard Space Flight Center, who designed the observations.

“The Hellas Basin is at a lower elevation, and therefore experiences higher atmospheric pressure. This higher pressure leads to a suppression of thermal emission at this particular wavelength range. [4.1-4.4 microns] due to an effect called pressure broadening. It will be very interesting to disentangle these competing effects in this data.”

It refers to the near-infrared spectrum of Mars, which shows a finer and more detailed breakdown of the composition of the planet’s atmosphere and surface, as specific wavelengths are attenuated or amplified by absorption and the re-emission of light by specific molecules.

So far, scientists have been able to easily identify carbon dioxide, carbon monoxide, and water in the Martian atmosphere.

However, the analysis is ongoing and we won’t know what details this new data reveals until the team is ready to release their findings in a published paper, which they are currently working on. This will have to go through the peer review and publication process, but we are excited to hear what new information the incredible telescope can reveal about such a well-studied planet.

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