Scientists have spent centuries pointing their instruments at Jupiter, and every now and then they make observations that not only further our understanding of the solar system’s largest planet, but astound us at the same time. Using what is known as the “lucky imaging” technique, scientists have created one of the sharpest infrared images of Jupiter ever taken from Earth, helping to reveal its weather systems, lightning and iconic Great Red Spot in exciting new detail.
The dramatic weather patterns of Jupiter have confounded researchers for a long time, with advances in instruments and scientific methods continually reshaping our understanding of these complex systems. The team at Hawaii’s Gemini Observatory has spent the past three years probing the gas giant’s many mysteries, and now through the use of "lucky imaging" has produced some significant findings.
This technique sees the Earth-based telescope used to snap a huge amount of ultra-short-exposure images. The team then picked out only the sharpest of the bunch, where Earth’s atmosphere is relatively stable, and used them to compile the impressive mosaic of Jupiter, made up of some of the sharpest infrared imagery ever taken of the planet from the ground.
“The Gemini data were critical because they allowed us to probe deeply into Jupiter’s clouds on a regular schedule,” says Michael Wong of UC Berkeley, who led the research team. “We used a very powerful technique called lucky imaging … these images rival the view from space.”
One advantage of using Gemini’s infrared capabilities to examine Jupiter is that the long wavelength of infrared light can penetrate its thinner haze, but is blocked in parts by the thicker clouds higher up in the atmosphere. This is what leads to the spooky “jack o'-lantern” effect in the mosaic image seen at the top of the page.
But the findings of this research do more than paint a pretty new picture of Jupiter, they also shed new light on the masses of clouds, lightning and gas that swirl across its surface. The infrared images were combined with visible light images from the Hubble Space Telescope, to offer new insights about the changing nature of the Great Red Spot.
The shape, size and appearance of the Great Red Spot, including the dark spots within it, have changed dramatically since scientists began observing it. These have been shown to pop up, disappear and change their shape over time, and why and how they do so has been a mystery in itself.
By comparing visible-light images from Hubble with infrared-light images from Gemini taken within a few hours of each other, the team says it is has come up with an explanation. The dark parts seen in visible light show up as very bright in infrared, suggesting they are actually holes in the cloud cover. The clearer areas, meanwhile, appear as very bright regions as the heat from the planet’s interior show up in infrared light and is unobscured by the clouds higher in the atmosphere.
"It's kind of like a jack-o'-lantern," says Wong. "You see bright infrared light coming from cloud-free areas, but where there are clouds, it's really dark in the infrared."
The scientists were also able to draw some interesting conclusions about lightning activity on Jupiter by turning to data from NASA’s Juno probe. As it orbited Jupiter, the unmanned spacecraft measured radio signals emitted by the powerful flashes of lightning taking place below. The locations of these events were overlaid with data from the Gemini and Hubble instruments so the team could investigate the cloud structures where they took place.
"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,” says Amy Simon of NASA's Goddard Space Flight Center. “The data from Hubble and Gemini can tell us how thick the clouds are and how deep we are seeing into the clouds.”
This enabled to team to demonstrate that the lightning flashes are driven by huge convective towers, created by upwelling moist air over water ice and liquid.
“Scientists track lightning because it is a marker of convection, the turbulent mixing process that transports Jupiter's internal heat up to the visible cloud tops,” says Wong. “Ongoing studies of lightning sources will help us understand how convection on Jupiter is different from or similar to convection in the Earth's atmosphere.”
The research was published in the The Astrophysical Journal Supplement Series.
Sources: Gemini Observatory, NASA