The international Gemini Observatory teams up with Hubble to support the Juno mission and bring new insights into Jovian weather.
Using the International Gemini Observatory, a team of researchers, using a technique knows as "Lucky Imaging" has recently captured some of the highest resolution images of Jupiter ever taken from the ground.
These images are part of a multi-year joint observing program with the Hubble Space Telescope in support of NASA’s Juno mission. The Gemini images, when combined with the Hubble and Juno observations, reveal that lightning strikes, and some of the largest storm systems that create them, are formed in and around large convective cells over deep clouds of water ice and liquid.
The new observations also confirm that dark spots in the famous Great Red Spot are actually gaps in the cloud cover and not due to cloud color variations.
Using "Lucky Imaging" to capture Jupiter's massive lightning storms:
The picture was captured in infrared by the Gemini North Telescope in Hawaii by the process of "Lucky Imaging"
Infrared is a longer wavelength than the more familiar visible light detected by the likes of the Hubble telescope. It is used to see past the haze and thin clouds at the top of Jupiter's atmosphere, to give scientists the opportunity to probe deeper into the planet's internal workings.
To achieve the resolution, scientists used a technique called "lucky imaging" which scrubs out the blurring effect of looking through Earth's turbulent atmosphere.
This method involves acquiring multiple exposures of the target and only keeping those segments of an image where that turbulence is at a minimum.
When all the "lucky shots" are put together in a mosaic, a clarity emerges that's beyond just the single exposure.
The observations :
The high-resolution images reveal that regions of cloud that appear darker in optical images actually glow the most brightly in infrared, indicating those regions have little to no cloud compared to the lighter bands.
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| This image showing the entire disk of Jupiter in infrared light was compiled from a mosaic of nine separate pointings observed by the international Gemini Observatory, a program of NSF’s NOIRLabon 29 May 2019. From a “lucky imaging” set of 38 exposures taken at each pointing, the research team selected the sharpest 10%, combining them to image one ninth of Jupiter’s disk. Stacks of exposures at the nine pointings were then combined to make one clear, global view of the planet. Even though it only takes a few seconds for Gemini to create each image in a lucky imaging set, completing all 38 exposures in a set can take minutes — long enough for features to rotate noticeably across the disk. In order to compare and combine the images, they are first mapped to their actual latitude and longitude on Jupiter, using the limb, or edge of the disk, as a reference. Once the mosaics are compiled into a full disk, the final images are some of the highest-resolution infrared views of Jupiter ever taken from the ground. [Credit: International Gemini Observatory/NOIRLab/NSF/AURA, M.H. Wong (UC Berkeley) and team Acknowledgments: Mahdi Zamani] |
"It's kind of like a jack-o-lantern," said astronomer Michael Wong, of the University of California, Berkeley. "You see bright infrared light coming from cloud-free areas, but where there are clouds, it's really dark in the infrared."
This included a line curving around the edge of the Great Red Spot, a permanent storm currently a little larger than an entire Earth. Similar features had been seen in the storm before, but it was unclear what was causing them.
Visible-light observation couldn't distinguish between darker cloud material, and thinner cloud cover over Jupiter's warm interior, so their nature remained a mystery," Said planetary scientist Glenn Orton, of NASA's Jet Propulsion Laboratory.
The new imagery cleared that question up rather neatly. When the two images were compared, a glowing infrared arc neatly matched up to an optical shadow, showing that the colouration marked a deep crack in the storm's swirling clouds.
That's really cool. But things got even more interesting when data from NASA's Jupiter orbiter Juno was thrown into the mix. As Juno orbits and makes close flybys of Jupiter's poles, it has been detecting atmospheric radio signals, called sferics and whistlers, from powerful lightning strikes.
In its first eight flybys, Juno's Microwave Radiometer Instrument detected 377 lightning discharges, clustered around the planet's polar regions. This is basically the opposite of Earth, where lightning storms are more common around the equator.
Planetary scientists believe that this has to do with how the Sun warms both planets. On both, the equator is warmed by the Sun. On Earth, this generates convection currents that drive tropical thunderstorms.
On Jupiter, which is much farther away from the Sun, equatorial warming is gentler, stabilising the upper atmosphere; but, scientists have theorised, this stabilising warmth doesn't reach the poles, so they're rather more tempestuous.
Combining this Juno data with the Gemini and Hubble images sheds more light on these wild storms, revealing the cloud structures around where lightning forms. "The data from Hubble and Gemini can tell us how thick the clouds are and how deep we are seeing into the clouds," explained planetary scientist Amy Simon of NASA.
The team found that the lightning strikes are generated in regions with large, convective towers of moist air over deep clouds of water, both frozen and liquid. Clear regions around these storms are probably caused by a downwelling of drier air outside the convection cells.
The Juno mission is ongoing, scheduled to end in July of next year. These findings will inform how to probe the data it is still collecting, as well as future ground- and space-based observations. And we are finally getting a handle on Jupiter's savage weather.
"Because we now routinely have these high-resolution views from a couple of different observatories and wavelengths, we are learning so much more about Jupiter's weather," Simon said.
"This is our equivalent of a weather satellite. We can finally start looking at weather cycles."
(The research has been published in The Astrophysical Journal Supplement Series.)
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