What Are Atmospheres Like on Other Planets?

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Examining planetary systems and the origin of life is one of the James Webb Space Telescope's core goals.


Mars visible and infrared light
This visible-light image of Mars (left) shows what the human eye would see. The infrared image (right) reveals features that could not be seen in visible light, including variations in the abundance and distribution of water-bearing minerals. CREDIT: J. Bell (Cornell University), J. Maki (JPL), M. Wolff (Space Sciences Institute), NASA. GET THE FULL IMAGE IN RESOURCE GALLERY >

From weather patterns to water molecules, study of Earth’s atmosphere tells us a lot about our planet’s present, future, and past. But what about the atmospheres of our planetary neighbors? There is still much to discover about these other worlds—how they differ from Earth and how they are similar.

Examining planetary systems and the origin of life is one of the James Webb Space Telescope’s core goals. Webb’s focus on the infrared portion of the electromagnetic spectrum provides astronomers with the ability to resolve features of planet surfaces and atmospheres they could not see in visible light.

Our Closest Neighbor

The presence of water on Mars now and in the past is one of the driving forces for Martian exploration. Webb will help us to understand Mars’ atmosphere, and conduct studies that verify findings of the Mars rovers and landers. Does the atmosphere of Mars reveal a more habitable past? Is it habitable now? What processes altered the stability of its atmosphere? In addition to searching for water, geologists will use Webb to study the formation and evolution of global dust storms and cloud systems over dormant volcanoes, and search for traces of chemical changes in the atmosphere. Mars’ history and potential future as a water-bearing planet may yield insights into Earth’s own story, especially the evolution of life.

Outer Planets

Shoemaker-Levy 9 slams Jupiter, July 1994
In July 1994, 21 chunks of comet Shoemaker-Levy 9 slammed into Jupiter. The Hubble telescope recorded this spectacular event. CREDIT: R. Evans, J. Trauger, H. Hammel and the HST Comet Science Team and NASA.

Looking farther, to the outer Solar System, Webb’s observations will give us a better picture of the seasonal weather and climate on the giant gas planets and their moons. Saturn’s moon Titan, with its lakes of liquid methane, is a good example. Webb will be an important tool for keeping track of the slowly changing seasons on Titan, which orbits the Sun with Saturn only every 29.5 Earth years. Webb will reveal the interplay of chemistry and atmospheric dynamics in response to the shift of Titan’s seasons. To probe Titan’s complex chemistry, Webb will investigate the composition of the atmosphere, watch clouds, track hazes, and monitor changes on the surface that occur with precipitation, geologic activity, or sea shrinkage.

Webb also offers unprecedented observing opportunities in near- and mid-infrared wavelengths for Jupiter, Saturn, Uranus, and Neptune. Webb’s infrared capabilities can be used to probe different depths in these atmospheres, mapping cloud structures and major storm systems, as well as their evolution, with finer detail than previously possible. Webb will also enable mapping of organic molecules across the disks of Uranus and Neptune for the first time, providing insight into the composition and circulation of their atmospheres. These investigations will reveal whether atmospheric changes are consequences of seasons, local weather, or solar activity. And if a comet or meteor strikes a planet, as the comet Shoemaker-Levy 9 did on Jupiter in 1994, Webb will be on hand to track the atmospheric changes that result.

Artist's Impression of a Kuiper Belt Object
This artist’s illustration shows a Kuiper Belt object located on the outer rim of our solar system, about 4 billion miles from the Sun. CREDIT: NASA, ESA, and G. Bacon (STScI).

Small Wonders

Finally, asteroids and other small bodies in our solar system possess features that Earth-based observatories are blind to, but that Webb will be able to identify by analyzing those objects in infrared light. Webb will also help us learn more about the composition and mineralogy of these rocky objects. Webb will follow-up on NASA’s New Horizons mission in investigating some of the most distant objects in our solar system, including the dwarf planet Pluto.

Last Updated: May 31, 2018

Keywords:  Exoplanets

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