 "Planet, Jupiter")
Jupiter's Great Red Spot with its swirl of reddish hues may be the mysterious heat source behind the planet's surprisingly high upper atmospheric temperatures, new NASA-funded research suggests.
The Great Red Spot (GRS) has delighted and mystified since its discovery in the 17th Century.
It is two-three times as wide as Earth and is seen by many as a "perpetual hurricane" with winds peaking at about 400 miles an hour.
Here on Earth, sunlight heats the atmosphere at altitudes well above the surface - for example, at 250 miles above our planet where the International Space Station (ISS) orbits.
Scientists have been stumped as to why temperatures in Jupiter's upper atmosphere are comparable to those found at Earth, yet Jupiter is more than five times the distance from the Sun.
Researchers from Boston University's Center for Space Physics set out to solve the mystery by mapping temperatures well above Jupiter's cloud tops using observations from Earth.
They analysed data from the SpeX spectrometer at NASA's Infrared Telescope Facility (IRTF) on Mauna Kea, Hawaii.
By observing non-visible infrared light hundreds of miles above the gas giant, scientists found temperatures to be much higher in certain latitudes and longitudes in Jupiter's southern hemisphere, where the spot is located.
"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?" said James O'Donoghue from Boston University.
The study, appeared in the journal Nature, found that the storm in the Great Red Spot produces two kinds of turbulent energy waves that collide and heat the upper atmosphere.
Gravity waves are much like how a guitar string moves when plucked, while acoustic waves are compressions of the air (sound waves).
Heating in the upper atmosphere 500 miles above the Great Red Spot is thought to be caused by a combination of these two wave types "crashing," like ocean waves on a beach.
"The extremely high temperatures observed above the storm appear to be the 'smoking gun' of this energy transfer," said O'Donoghue.
"This tells us that planet-wide heating is a plausible explanation for the 'energy crisis,' a problem in which upper-atmospheric temperatures are measured hundreds of degrees hotter than can be explained by sunlight alone," he pointed out.
This effect has been observed over the Andes Mountains here on Earth and may also be happening elsewhere in the outer solar system.
Scientists believe this phenomenon also occurs on giant exoplanets orbiting other stars.
NASA's Juno spacecraft, which recently arrived in Jupiter's orbit, will have several opportunities during its 20-month mission to observe the Great Red Spot and the turbulent region surrounding it.
