Atmospheric Science

In addition to the suite of remote sensing instruments carried aboard the Juno spacecraft, the mission coincides with an unprecedented international campaign to scrutinise Jupiter’s dynamic, evolving atmosphere from Earth-based facilities.

Juno carries a microwave radiometer capable of sounding below Jupiter’s top-most cloud decks to hundreds of bars of pressure to understand the deep processes underpinning the giant planet’s complex meteorology and climate, a near-infrared spectrometer to study the distribution of gaseous species within the weather layer, an ultraviolet spectrograph that can probe the structure, chemistry and aerosols of Jupiter’s upper stratosphere, and a four-filter camera dedicated to providing close-up views of interesting features for the purpose of education and public outreach.

However, Juno’s close-in orbital trajectory means that these experiments may only observe on regional scales (building up a global picture over time), and the duration of the mission is short compared to the timescales of Jupiter’s climate variability (one year on Jupiter lasts 11.9 Earth years). To address this, Dr Leigh Fletcher, Senior Lecturer in Planetary Science in the Department of Physics and Astronomy at Leicester, is part of an international team employing world-class observatories to provide the global spatial and temporal context to aid in understanding Jupiter’s atmosphere during the Juno epoch.

Dr Fletcher, with the assistance of Research Fellow Henrik Melin, is leading an infrared ground-based campaign that will examine wavelength ranges that are inaccessible to Juno’s instrumentation, providing unique spatial, temporal and spectral coverage of the giant planet’s atmosphere in the coming years.

Dr Leigh Fletcher discusses the search for water in Jupiter's atmosphere on the BBC's Sky at Night programme.

The ground-based infrared observing campaign led by Leicester is already underway, providing a characterisation of the Jovian atmosphere before Juno’s arrival by employing NASA’s Infrared Telescope Facility (IRTF) and the Japanese Subaru Telescope in Hawaii, the European Southern Observatory’s Very Large Telescope (VLT) in Chile, and the SOFIA stratospheric observatory (a converted 747 aircraft).

The infrared observations are being coordinated with millimetre-wave observations from ALMA, centimetre-wave observations from the VLA, near-infrared observations from the Keck and Gemini observatories, and visible-light observations from the global network of amateur astronomers. These observations will be used to provide frequent, global maps of Jupiter’s atmospheric temperatures, winds and dynamics, the distributions of chemical species related to cloud condensation, vigorous dynamical mixing and stratospheric photochemistry, and profiling of Jupiter’s multiple cloud decks and hazes.

Each of these parameters will be used to set Juno’s findings into the wider context of Jovian climate variability, building on expertise gained using Cassini’s observations of Saturn’s atmosphere. The campaign relies on techniques that we have used over the past decade to explore the vertical structure of Jupiter’s Great Red Spot, the aftereffects of an asteroid collision in 2009, the origins of the planet’s atmosphere via measurements of its nitrogen content, the causes of global upheavals of Jupiter’s banded structure, and the cloud structure of Jupiter’s weather layer.

The observations led from Leicester will directly connect the environmental conditions in Jupiter’s cloud-forming region with Juno’s discoveries in both the deep, dynamic regions below the clouds and with the energetics of the upper atmosphere and auroras.

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