The planets: what can JWST tell us?
Despite centuries of observation, the planets still hold mysteries. Here is what the JWST will aim to reveal about each one
an observing window of around 50 days approximately every six months, the giant planets Jupiter, Saturn, Uranus and Neptune will all be viewable, as well as their associated rings and 170 known moons.
While the planets themselves will be monitored by JWST, some of the most interesting science will concern their satellites. From helping to solve the tidal heating conundrum on Jupiter’s moon Io to taking over the task of watching the Saturnian moon Titan after the Cassini mission comes to an end or even establishing whether Neptune’s retrograde-orbit moon Triton has a subsurface ocean, JWST offers the chance to view and try to understand the most dynamic processes of the Solar System’s satellites.
Focus on the small things
However, the bread and butter for JWST’s Solar System science will be even less studied, smaller and distant bodies: comets, the main belt asteroids situated between Mars and Jupiter, the Trojan asteroids that share Jupiter’s orbit, and the Kuiper Belt objects – including dwarf planet Pluto and the yet-to-be-seen Planet Nine. All could yield clues to how the Solar System came to be the home we know.
“Because they retain material from the very start of Solar System history, they reveal the chemical makeup of the planets and how planets form,” says Andy Rivkin, planetary astronomer from Johns Hopkins University.
For these smaller distant bodies and ring systems, NASA has another trick
up its sleeve: stellar occultations, where a star is temporarily blocked by a passing Solar System body.
“If you can take data very quickly as an object passes in front of a star, you can measure various things about the object itself,” explains Stansberry. By looking at the changes to the star’s light as it disappears behind a planet, Webb will be able to look at ring microstructures, and may discover rings around minor planets or even find atmospheres around various Kuiper Belt objects.
All of these proposed targets for Webb suggest the Solar System’s most wellhidden mysteries may soon be solved, but one paper really sticks out as having the potential to captivate the public’s imagination. In it, the authors propose using JWST and Hubble together to create stereo 3D movies of the planets and moons amateur astronomers have been fascinated by for centuries.
“I worked with a vision scientist colleague to understand the limits of human depth perception,” says Joel Green, a project scientist at STScI, who led the study. “It turned out that if you had eyes one million miles apart, and the resolution of Hubble and Webb (roughly 1,000 times better than 20/20 vision), you could actually see objects like Mars, or Jupiter’s moon system or Saturn’s rings in stereo 3D!”
Not only might this be a boon to astronomers, offering stereo data on weather changes, collisional studies, ring system shocks, and many more, but would also be a first for science education, making ancient astronomical bodies come to life in the classroom. As Green notes: “These are the sorts of images that could inspire a generation”.
Does Neptune’s moon Triton harbour an ocean beneath its crust? JWST could tell us
How much more might we learn about Pluto and other Kuiper Belt objects once JWST is trained on them?