NASA Scientists Identify Missing Wave near Jupiter’s Equator (above photo)
April 17, 2015: In the clouds of Jupiter, scientists have found evidence of a type of atmospheric wave that had long been proposed but had not been identified in images before now. Researchers consider this kind of wave, called a Kelvin wave, a fundamental part of a planetary atmosphere, so the absence of one on Jupiter has long been a mystery. In Earth’s atmosphere, Kelvin waves are involved in a tropical wind pattern whose influence can reach as far as the polar vortex.
“Scientists had looked for this type of wave in images of Jupiter from other missions, without luck,” said Amy Simon, a planetary scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “Sometimes, we found a different type of wave. Other times, we couldn’t be sure we had a wave at all.”
The presence of Jupiter’s wave was indicated by a series of banded clouds, spotted in images obtained by the Ralph multispectral imager when NASA’s New Horizons spacecraft flew by the planet in 2007.
The striking pattern of light and dark stripes was captured in a series of images, allowing researchers to determine the extent and speed of the wave. At that time, the team determined that the pattern stretched through the entire area visible to the imager (about one-quarter of the circumference at the equator) and probably went all the way around the planet.
In a new analysis of those images, a trio of researchers from NASA and the University of Houston has calculated that the wave was moving at about 367 to 393 miles per hour (164 to 176 meters per second). This is slower than previously thought but still much faster than the already speedy background winds near the equator. The pattern appears to cast shadows, which may indicate that it is higher in the troposphere than the other clouds, or possibly in the stratosphere.
When the New Horizons images were first studied, scientists had classified the feature as a gravity-inertia wave, but the newer analysis indicates that a Kelvin wave is more likely. The wavelength in this case is about 186 miles (300 kilometers), which is short compared to Kelvin waves in Earth’s atmosphere.
The researchers looked for evidence of small-scale waves in Jupiter images from other missions. Such a pattern would not be big enough to show up in images taken by Hubble, the researchers determined. The Cassini spacecraft should have been able to see this kind of feature, but images from those flybys don’t contain evidence of a similar wave. Much smaller groups of waves show up in images taken when the Voyagers flew by and when Galileo orbited the planet, but they occur further from the equator than expected for a Kelvin wave.
The structure of a Kelvin wave is determined by a balance between the Coriolis force generated by the planet’s rotation and a boundary of some kind. In Earth’s oceans, that boundary could be the coastline. In a planet’s atmosphere, the zone near the equator serves as a boundary.
In Earth’s atmosphere, Kelvin waves contribute to the quasi-biennial oscillation, a pattern of tropical winds in the stratosphere. About every two to three years, the wind shifts from easterly to westerly— accompanied by changes in temperature—and back again. The influence of this pattern sometimes can be felt as far away as the northern or southern polar vortex.
An analogous pattern of global winds and temperatures has been found in Jupiter’s stratosphere. This pattern, the quasi-quadrennial oscillation, repeats every four to five Earth years. A similar pattern on Saturn repeats roughly every 15 Earth years.
“The situation is more complicated on Earth because of the large land masses, seasons, and other factors,” said Simon. “But we can use Jupiter almost like a lab experiment in this case. We can show that the oscillating pattern can be forced with the wave motions alone.”
This research is available online in Geophysical Research Letters.
This work was funded in part by NASA’s Planetary Atmospheres Program. The Johns Hopkins University Applied Physics Laboratory (APL) manages the New Horizons mission for NASA’s Science Mission Directorate in Washington. Alan Stern of the Southwest Research Institute, headquartered in San Antonio, is the principal investigator and leads the mission. New Horizons is part of the New Frontiers Program managed by NASA’s Marshall Space Flight Center in Huntsville, Alabama. APL designed, built and operates the spacecraft.
In this image, a view of Jupiter and Io captured by NASA’s New Horizons spacecraft in 2007 en route to Pluto.
Image Credit: NASA
NASA Messenger Spacecraft Achieves Unprecedented Success Studying Mercury (above photo)
After extraordinary science findings and technological innovations, a NASA spacecraft launched in 2004 to study Mercury will impact the planet’s surface, most likely on April 30, after it runs out of propellant.
NASA’s MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft will impact the planet at more than 8,750 miles per hour (3.91 kilometers per second) on the side of the planet facing away from Earth. Due to the expected location, engineers will be unable to view in real time the exact location of impact.
On Tuesday, mission operators in mission control at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland, completed the fourth in a series of orbit correction maneuvers designed to delay the spacecraft’s impact into the surface of Mercury. The last maneuver is scheduled for Friday, April 24.
“Following this last maneuver, we will finally declare the spacecraft out of propellant, as this maneuver will deplete nearly all of our remaining helium gas,” said Daniel O’Shaughnessy, mission systems engineer at APL. “At that point, the spacecraft will no longer be capable of fighting the downward push of the sun’s gravity.”
Although Mercury is one of Earth’s nearest planetary neighbors, little was known about the planet prior to the MESSENGER mission.
“For the first time in history we now have real knowledge about the planet Mercury that shows it to be a fascinating world as part of our diverse solar system,” said John Grunsfeld, associate administrator for the Science Mission Directorate at NASA Headquarters in Washington. “While spacecraft operations will end, we are celebrating MESSENGER as more than a successful mission. It’s the beginning of a longer journey to analyze the data that reveals all the scientific mysteries of Mercury.”
The spacecraft traveled more than six and a half years before it was inserted into orbit around Mercury on March 18, 2011. The prime mission was to orbit the planet and collect data for one Earth year. The spacecraft’s healthy instruments, remaining fuel, and new questions raised by early findings resulted in two approved operations extensions, allowing the mission to continue for almost four years and resulting in more scientific firsts.
One key science finding in 2012 provided compelling support for the hypothesis that Mercury harbors abundant frozen water and other volatile materials in its permanently shadowed polar craters.
Data indicated the ice in Mercury’s polar regions, if spread over an area the size of Washington, would be more than two miles thick. For the first time, scientists began seeing clearly a chapter in the story of how the inner planets, including Earth, acquired water and some of the chemical building blocks for life.
A dark layer covering most of the water ice deposits supports the theory that organic compounds, as well as water, were delivered from the outer solar system to the inner planets and may have led to prebiotic chemical synthesis and, thusly, life on Earth.
“The water now stored in ice deposits in the permanently shadowed floors of impact craters at Mercury’s poles most likely was delivered to the innermost planet by the impacts of comets and volatile-rich asteroids,” said Sean Solomon, the mission’s principal investigator, and director of Columbia University’s Lamont-Doherty Earth Observatory in Palisades, New York. “Those same impacts also likely delivered the dark organic material.”
In addition to science discoveries, the mission provided many technological firsts, including the development of a vital heat-resistant and highly reflective ceramic cloth sunshade that isolated the spacecraft’s instruments and electronics from direct solar radiation – vital to mission success given Mercury’s proximity to the sun. The technology will help inform future designs for planetary missions within our solar system.
“The front side of the sunshade routinely experienced temperatures in excess of 300° Celsius (570° Fahrenheit), whereas the majority of components in its shadow routinely operated near room temperature (20°C or 68°F),” said Helene Winters, mission project manager at APL. “This technology to protect the spacecraft’s instruments was a key to mission success during its prime and extended operations.”
The spacecraft was designed and built by APL. The lab manages and operates the mission for NASA’s Science Mission Directorate. The mission is part of NASA’s Discovery Program, managed for the directorate by the agency’s Marshall Space Flight Center in Huntsville, Alabama.
For a complete listing of science findings and technological achievements of the mission visit: www.nasa.gov/messenger
NASA’s MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft traveled more than six and a half years before it was inserted into orbit around Mercury on March 18, 2011.
Credit: NASA/JHU APL/Carnegie Institution of Washington
“Cat face universe!” (above)
Not even the great universe or an astronomy blog post can escape the multi-dimensional and far-reaching effects of #Caturday.
On the BaLang Mountains located in Sichuan province of southwest China, the zodiacal light extends above the western horizon and seems to end at the lovely Pleiades star cluster and California Nebula.
Credit: Tony Pan
Image Date: December 13, 2014