The James Webb Space Telescope’s main goal is to detect faint light from distant galaxies, but it recently observed one of the brightest objects in the night sky: Mars.
The space observatory captured its first images and data of the red planet on September 5.
Multiple orbiters above Mars, and the land-bound rovers Curiosity and Perseverance, roam the surface, regularly send back insights. Webb’s infrared capabilities contribute another perspective that could reveal details about the Martian surface and atmosphere.
Webb, located a million miles (1.6 million kilometres) from Earth, can spot the sunlit side of Mars that faces the space telescope, which puts the observatory in the perfect position to spy the planet’s seasonal changes, dust storms and weather all at once.
The telescope is so sensitive that astronomers had to make adjustments to prevent the blinding infrared light of Mars from saturating Webb’s detectors. Instead, Webb observed Mars using very short exposures.
The new images depict Mars’ eastern hemisphere in different wavelengths of infrared light. To the left is a reference map of the hemisphere captured by the Mars Global Surveyor mission, which ended in 2006.
The top-right image from Webb shows reflected sunlight on the Martian surface, showcasing Martian features like the Huygens Crater, dark volcanic rock and the Hellas Planitia, a massive impact crater on the red planet that stretches for more than 1,200 miles (2,000 kilometres).
The lower-right image shows the thermal emission of Mars, or the light emitted by the planet as it loses heat. The brightest areas indicate the warmest spots. Additionally, astronomers spotted something else in the thermal emission image.
When this thermal light passes through the Martian atmosphere, some of it is absorbed by carbon dioxide molecules. This phenomenon has caused the Hellas Planitia to appear darker.
“This is actually not a thermal effect at Hellas,” said Geronimo Villanueva, a planetary scientist at NASA’s Goddard Space Flight Center, in Greenbelt, Maryland, in a statement.
“The Hellas Basin is a lower altitude, and thus experiences higher air pressure,” said Villanueva, who is also the principal investigator of Mars and Ocean Worlds studies for Webb. “That higher pressure leads to a suppression of the thermal emission at this particular wavelength range due to an effect called pressure broadening. It will be very interesting to tease apart these competing effects in these data.”
With Webb’s powerful capabilities, Villanueva and his team also captured the first near-infrared spectrum of Mars.
The spectrum indicates more subtle differences in brightness across the planet, which could highlight aspects of the Martian surface and atmosphere. An initial analysis has revealed information about icy clouds, dust, rock types on the surface and the composition of the atmosphere contained in the spectrum. There are also signatures of water, carbon dioxide and carbon monoxide.
The NASA research team will share more about Webb’s observations of Mars in a study that will be submitted for peer review and publication in the future. And the Mars team is looking forward to using Webb’s capabilities to pick out the differences between regions on the red planet and search for gases like methane and hydrogen chloride in the atmosphere.