First images of Mars from the James Webb Space Telescope reveal the secrets of the atmosphere

The James Webb Space Telescope (JWST) has captured its first images of Mars, observing infrared light coming from the red planet with high sensitivity.

The first images and spectra of Mars from the James Webb Space Telescope were published on Monday September 19 during the Europlanet scientific congress (opens in a new tab) (EPSC) 2022. The images and measurements were taken September 5, 2022 from JWST’s position approximately one million miles (1.6 million kilometers) from Mars.

Images of Mars’ observable disk – the side of the planet lit by the sun and facing the telescope – were captured by Webb’s Near infrared camera (opens in a new tab) (NIRCam) and could provide planetary scientists with a unique view of Earth’s near neighbor, providing data that can be used in conjunction with observations made by rovers like NASA’s Perseverance and craft in Mars orbit.

Related: The James Webb Space Telescope takes its first direct photo of an alien world

Because Mars is relatively close and very bright, it’s not the easiest object for the JWST to view – designed to see incredibly distant and faint objects.

“Mars is so bright that the challenge is how to see it,” said Giuliano Liuzzi, a scientist and principal investigator of NASA’s Planetary Systems Laboratory at Goddard Space Flight Center, during an EPSC press conference to mark the publication of images.

To prevent the bright infrared light from Mars from blinding the JWST instruments, the scientists used very short exposures to observe the red planet. This involved measuring only a portion of the light that reached JWST’s detectors, and then applying special methods to analyze the collected data.

“We can see this incredible resolution, we have the diffraction limit of a space telescope in the infrared, which is fantastic. We can see the whole planet,” Liuzzi continued.

Observing Mars 24 hours a day

The JWST was able to capture images and spectra with the spatial resolution astronomers need to study near-term phenomena such as Martian weather patterns, dust storms, and even changes caused by the planet’s seasons.

Additionally, the Webb Telescope could capture events that occur at different times of the Martian day – during the day, at sunset, and during the night – in a single observation.

The first images of Mars taken by the JWST show an area of ​​the planet’s eastern hemisphere in two different wavelengths of light.

The short-wavelength image is dominated by reflected sunlight and shows details of the Martian surface that resemble features seen in visible light. These features include the Huygens Crater, an impact crater nearly 280 miles wide (450 kilometers) and dark volcanic rock in the Syrtis Major Planum.

The Webb Space Telescope’s NIRCam camera captured the light that Mars emits at longer infrared wavelengths as it loses heat. The brightness of this light is tied to the temperature of Mars and its atmosphere, with the brightest and hottest area being located where the sun is nearly overhead.

The luminosity decreases towards the Martian polar regions which are less exposed to the sun, and in the northern hemisphere of the planet which is currently in the middle of the Martian winter.

However, the amount of light reaching the JWST is not only related to the temperature of the planet. The images collected by the telescope can also give indications of the chemical composition of the Martian atmosphere and surface.

Atmospheric indices at Hella Basin

Analysis of the spectrum of light detected from Mars with data collected by the James Webb Space Telescope could help astronomers determine the composition of its atmosphere and surface.

After analyzing images from the JWST, Liuzzi and his team found that the 1,200-mile (1,930 km) wide Hellas Basin appears darker than its surroundings, even at the hottest time of the Martian day in this region.

“One of the interesting things is that you can see a dark spot which is a basin on Mars. We didn’t expect that. We were seeing something very bright, but it got darker,” Liuzzi said. “It’s actually not a thermal effect in Hellas.”

The darkening observed on this well-preserved impact structure is the result of light passing through the Martian atmosphere and being absorbed by carbon dioxide.

“The Hellas basin is at a lower altitude and therefore experiences higher atmospheric pressure,” explains the Goddard researcher. “This higher pressure results in a suppression of thermal emission in this particular wavelength range due to an effect called pressure broadening. It will be very interesting to distinguish these competing effects in this data.”

The new images also demonstrate the ability of the James Webb Space Telescope to study Mars using a technique called spectroscopy on measurements taken with the telescope’s Near Infrared Spectrograph (NIRSpec) instrument.

The first near-infrared spectrum of Mars from the James Webb Space Telescope, captured by the Near-Infrared Spectrograph (NIRSpec) on September 5, 2022. (Image credit: NASA, ESA, CSA, STScI, Mars Team JWST/GTO)

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Because chemical elements absorb and emit light at very specific wavelengths, planetary scientists can use spectroscopy to study the “fingerprints” that different chemicals leave in the light passing through a planet’s atmosphere to determine its composition.

The first results obtained by the scientists show spectral characteristics coded with information about Martian dust, icy clouds, the composition of the atmosphere and the type of rocks found on the surface of the planet.

JWST observations should identify the presence of water, carbon dioxide, carbon monoxide and other chemical compounds.

Liuzzi pointed to the debate over the presence of methane on Mars, with early ground-based observations and rovers providing evidence for the compound, albeit sporadically. Although measurements from the ExoMars Trace Gas Orbiter (TGO) were unable to confirm this, and observations from Earth are complicated by methane in our planet’s atmosphere, Liuzzi believes that observations from the JWST could make the difference.

“The big puzzle is that the rovers on the surface and the observational data left a gap between zero and 10 kilometers [6 miles]”, he said.” Now we have James Webb we can see the full column [of the atmosphere] to the surface where the rover is. So we’ve provided a new way to solve this puzzle.”

Methane is important, Liuzzi added, because it can tell planetary scientists about many geological processes on Mars, including whether something big recently hit the Red Planet from space. Methane could also hint at biological activity in the planet’s ancient history.

“That’s our main focus right now,” Liuzzi said.

The JWST team is currently producing a paper outlining their findings for peer review.

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