James Webb took his first images of Mars, but why are they so “ugly”?

The James Webb Space Telescope has taken its first-ever shots of Mars. Compared to previous images of nebulae and galaxies, these visuals are almost disappointing. Why does their quality contrast so much with the other photos?

After having immortalized sumptuous images of nebulae or galaxies, the James Webb telescope delivers its new snapshot. And, we can be a little surprised that it is not as striking as the previous ones, because its subject is, for once, very close: it is the planet Mars which appears on these new images, presented September 19, 2022 by NASA.

The telescope obtained two views of the planet: a close-up that shows features on the surface of Mars, such as a crater or a basin, as well as a “thermal map” on which we see the radiance emitted by the star when it loses heat. Both pictures were taken on September 5.

On the left, a reference map. Webb’s images are on the right. // Source : NASA, ESA, CSA, STScI, Mars JWST/GTO team

The space telescope is blinded by Mars

The quality of these images is surprising: they are not as spectacular as the previous ones. They appear almost blurry and runny to us. But taking images of Mars is not the same for the JWST as imaging a distant galaxy, reminded NASA. ” Webb was built to detect faint light from distant galaxies, but Mars is extremely bright! Special techniques were used to prevent Webb from being flooded with light. »

The planet being very close, it is very luminous, both in visible light and in the infrared (an area in which Webb excels). However, the telescope is designed to see very distant celestial objects, with a tenuous glow. In other words, Webb’s instruments are so sensitive that the light from Mars is blinding to the observatory. ” James Webb is blinded by the beauty of Mars », nicely described Thomas Zurbuchen, astrophysicist and NASA associate administrator.

This does not prevent the telescope from being able to provide very interesting data on Mars, from its position 1.5 million kilometers from Earth. From there, James Webb can see the disk of Mars illuminated by the Sun. The resulting images and spectra should make it possible to capture short-term phenomena that occur on the planet, such as dust storms or seasonal changes. They will also be used to better understand the temperature variations between day and night on Mars (on which the day lasts a little longer than on Earth, 24 hours and 37 minutes).

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