NASA’s Hubble Space Telescope and the ground-based Gemini Observatory in Hawaii have teamed up with the Juno spacecraft to probe the mightiest storms in the solar system, taking place more than 500 million miles away on the giant planet Jupiter.
A team of researchers led by Michael Wong at the University of California in Berkeley, and including Amy Simon of NASA’s Goddard Space Flight Center, are combining multi-wavelength observations from Hubble and Gemini with close-up views from Juno to gain new insights into turbulent weather on this distant world. The results were published in April in The Astrophysical Journal Supplement Series.
“We want to know how Jupiter’s atmosphere works,” Wong said. The constant Jovian storms are gigantic compared to those on Earth, with thunderheads reaching 40 miles from base to top – five times taller than typical thunderheads on Earth – and powerful lightning flashes up to three times more energetic than Earth’s largest “superbolts.”
Like lightning on Earth, Jupiter’s lightning bolts act like radio transmitters, sending out radio waves as well as visible light when they flash across the sky.
Every 53 days, Juno races low over the storm systems, detecting radio signals known as “sferics” and “whistlers,” which can be used to map lightning even on the planet’s day side or from deep clouds where flashes are not otherwise visible. Meanwhile, Hubble and Gemini watch from afar, capturing high-resolution global views of the planet that are key to interpreting Juno’s close-up observations.
“Juno’s microwave radiometer probes deep into the planet’s atmosphere by detecting high-frequency radio waves that can penetrate through the thick cloud layers,” Simon said. “The data from Hubble and Gemini can tell us how thick the clouds are and how deep we are seeing into the clouds.”
By mapping lightning flashes detected by Juno onto optical images taken by Hubble and thermal infrared images captured at the same time by Gemini, researchers have shown that lightning outbreaks are associated with a three-way combination of structures: deep clouds made of water; large convective towers caused by upwelling of moist air; and clear regions presumably caused by downwelling of drier air outside convective towers.
Wong thinks lightning is common in turbulent areas known as folded filamentary regions. “These cyclonic vortices could be internal energy smokestacks, helping release internal energy through convection,” he said.
The ability to correlate lightning with deep water clouds also gives researchers another tool for estimating the amount of water in Jupiter’s atmosphere, which is vital for learning how such gas and ice giants formed – and thus the solar system as a whole.
While much has been gleaned about Jupiter from previous space missions, many details – including how much water is in the deep atmosphere, exactly how heat flows from the interior and what causes certain cloud colors and patterns – remain a mystery. The new findings provide insight into the atmosphere’s dynamics and three-dimensional structure.
With Hubble and Gemini observing Jupiter more frequently during the Juno mission, scientists also can study short-term changes like those in the Great Red Spot. It was not clear from previous missions whether dark features in the spot, which appear, disappear and change shape over time, are caused by some unidentified material in the high cloud layer, or if they are gaps in the clouds themselves – windows into a darker layer below.
Now, with the ability to compare visible-light images from Hubble with thermal infrared images from Gemini captured within hours of each other, it is possible to answer the question. Regions that are dark in visible light are very bright in infrared, indicating they are, in fact, holes in the cloud layer, from which heat rising from Jupiter’s interior is free to escape into space – and therefore appears bright in Gemini images.
“It’s kind of like a jack-o-lantern,” Wong said. “You see bright infrared light coming from cloud-free areas, but where there are clouds, it’s really dark in the infrared.”
Hubble and Gemini monitor the planet as a whole, providing real-time base maps in multiple wavelengths for reference for Juno’s measurements in the same way that Earth-observing weather satellites provide context for the National Oceanic and Atmospheric Administration’s high-flying hurricane hunters. Regular imaging of Jupiter by Hubble and Gemini in support of Juno is proving valuable for studying other weather phenomena as well, including changes in wind patterns, characteristics of atmospheric waves and circulation of various gases in the atmosphere.
Because Hubble and Gemini observations have proved so valuable for interpreting Juno data, Wong and his colleagues are making all their processed data readily accessible to other researchers through the Mikulski Archives for Space Telescopes at the Space Telescope Science Institute in Baltimore.
Goddard manages Hubble, a joint project between NASA and the European Space Agency. Science operations are led by the Space Telescope Science Institute. Marshall Space Flight Center was responsible for Hubble’s overall design, development and construction. Juno is part of NASA’s New Frontiers Program, which is managed by Marshall for the agency’s Science Mission Directorate. NASA’s Jet Propulsion Laboratory manages the Juno mission for the Southwest Research Institute in San Antonio.