Jupiter’s Great Red Spot heats planet’s upper atmosphere
Researchers from Boston University's (BU) Center for Space Physics report today (27 July) in Nature that Jupiter's Great Red Spot may provide the mysterious source of energy required to heat the planet's upper atmosphere to the unusually high values observed. The work, led by Dr James O'Donoghue of BU, was kick-started by a small travel grant (of just £500) from the Royal Astronomical Society back in 2012.
International Space Station orbits. Jupiter is over five times more distant from the Sun, and yet its upper atmosphere has temperatures, on average, comparable to those found at Earth. The sources of the non-solar energy responsible for this extra heating have remained elusive to scientists studying processes in the outer solar system.Sunlight reaching Earth efficiently heats the terrestrial atmosphere at altitudes well above the surface—even at 250 miles high, for example, where the
"With solar heating from above ruled out, we designed observations to map the heat distribution over the entire planet in search for any temperature anomalies that might yield clues as to where the energy is coming from," explained O'Donoghue, a research scientist at BU.
Astronomers measure the temperature of a planet by observing the non-visible, infrared (IR) light it emits. The visible cloud tops we see at Jupiter are about 30 miles above its rim; the IR emissions used by the BU team came from heights about 500 miles higher. When the BU observers looked at their results, they found high altitude temperatures much larger than anticipated whenever their telescope looked at certain latitudes and longitudes in the planet's southern hemisphere.
"We could see almost immediately that our maximum temperatures at high altitudes were above the Great Red Spot far below—a weird coincidence or a major clue?" O'Donoghue added.
Jupiter's Great Red Spot (GRS) is one of the marvels of our solar system. Discovered within years of Galileo's introduction of telescopic astronomy in the 17th Century, its swirling pattern of colourful gases is often called a "perpetual hurricane." The GRS has varied is size and colour over the centuries, spans a distance equal to three earth-diameters, and has winds that take six days to complete one spin. Jupiter itself spins very quickly, completing one revolution in only ten hours.
"The Great Red Spot is a terrific source of energy to heat the upper atmosphere at Jupiter, but we had no prior evidence of its actual effects upon observed temperatures at high altitudes," explained Dr Luke Moore, a study co-author and research scientist in the Center for Space Physics at BU.
Solving an "energy crisis" on a distant planet has implications within our solar system, as well as for planets orbiting other stars. As the BU scientists point out, the unusually high temperatures far above Jupiter's visible disk is not a unique aspect of our solar system. The dilemma also occurs at Saturn, Uranus and Neptune, and probably for all giant exoplanets outside our solar system.
"Energy transfer to the upper atmosphere from below has been simulated for planetary atmospheres, but not yet backed up by observations," O'Donoghue said. "The extremely high temperatures observed above the storm appear to be the 'smoking gun' of this energy transfer, indicating that planet-wide heating is a plausible explanation for the 'energy crisis.' "
O'Donoghue cites the help of the Royal Astronomical Society, when he was a PhD student, as being crucial to starting the work. "A £500 travel grant from the RAS, at a time of very tight funding, made it possible for me to carry out the observations on the SpeX instrument, mounted on the NASA Infrared Telescope Facility on Hawaii. This modest support helped me start my career in astronomy, which has taken me to Boston, and seen me publish my work in the world's leading scientific journals."
University of Leicester said: "Jupiter is a hot topic with Juno having just entered orbit at the planet. Leicester is home to the only UK group that is formally involved in this mission, and are directly involved with preparations for the JUICE mission, to be launched in 2022. We are very excited about the new science that these missions will bring."Co-author Dr Henrik Melin from the
Dr Tom Stallard, also from Leicester, and another co-author, added: "Our coordinated telescope observations of Jupiter are providing a global context to these space missions. This fantastic result, showing how the upper atmosphere is heated from below, was produced directly from Leicester's 2012 observing campaign, which was designed to try and answer why Jupiter's upper atmosphere is so hot. (The recent arrived NASA space probe) Juno will be measuring the aurora and its sources, and we expected the auroral energy to flow from the pole to the equator. Instead, we find the equator appears to be heated from plumes of energy coming from Jupiter's vast equatorial storms."
Dr James O'Donoghue, Lead Author
Dr Luke Moore, Second Author
Dr Roy Gal
Dr Tom Stallard
Dr Henrik Melin
Images and captions
https://www.ras.org.uk/images/stories/press/planets/Image 1bno_arrows_Jup_SuperHighRes_GRS_Art by Karen Teramura _ James ODonoghue_6705x4400.jpg
Notes for editors
The observations reported today and funded by NASA, were analysed by O'Donoghue and Moore in collaboration with colleagues Thomas Stallard and Henrik Melin from the University of Leicester's Department of Physics and Astronomy, in the UK. Data taken spanned nine hours on the night of December 4, 2012, at the Infrared Telescope Facility (IRTF) on Mauna Kea, Hawaii, which is operated by NASA and the University of Hawaii.
Founded in 1839, Boston University is an internationally recognized institution of higher education and research. With more than 33,000 students, it is the fourth-largest independent university in the United States. BU consists of 16 schools and colleges, along with a number of multi-disciplinary centres and institutes integral to the University's research and teaching mission. In 2012, BU joined the Association of American Universities (AAU), a consortium of 62 leading research universities in the United States and Canada.
The Royal Astronomical Society (RAS), founded in 1820, encourages and promotes the study of astronomy, solar-system science, geophysics and closely related branches of science. The RAS organizes scientific meetings, publishes international research and review journals, recognizes outstanding achievements by the award of medals and prizes, maintains an extensive library, supports education through grants and outreach activities and represents UK astronomy nationally and internationally. Its more than 4000 members (Fellows), a third based overseas, include scientific researchers in universities, observatories and laboratories as well as historians of astronomy and others.
Follow the RAS on Twitter