Ultraviolet and infrared images from NASA’s Cassini spacecraft and Hubble Space Telescope show active and quiet auroras at Saturn’s north and south poles.
Saturn’s auroras glow when energetic electrons dive into the planet’s atmosphere and collide with hydrogen molecules. Sometimes a blast of fast solar wind, composed of mostly electrons and protons, creates an active aurora at Saturn, as occurred on April 5 and May 20, 2013.
The first set of images, as seen in the ultraviolet part of the spectrum by Hubble, shows an active aurora dancing around Saturn’s north pole on April 5. The movie then shows a relatively quiet time between April 19 to 22 and between May 18 and 19. The aurora flares up again in Hubble images from May 20. This version, shown in false-color, has been processed to show the auroras more clearly.
A second set of ultraviolet images shows a closer view of an active north polar aurora in white. This set comes from Cassini ultraviolet imaging spectrograph observations on May 20 and 21.
The last set of images, in the infrared, shows a quiet southern aurora (in green) in observations from Cassini’s visual and infrared mapping spectrometer on May 17. Saturn’s inner heat glows in red, with dark areas showing where high clouds block the heat
This video will take you “Soaring Over Titan: Extraterrestrial Land of Lakes“:
This colorized movie from NASA’s Cassini mission takes viewers over the largest seas and lakes on Saturn’s moon Titan. The movie is made from radar data received during multiple flyovers of Titan from 2004 to 2013.
This colorized movie from NASA’s Cassini mission shows the most complete view yet of Titan’s northern land of lakes and seas. Saturn’s moon Titan is the only world in our solar system other than Earth that has stable liquid on its surface. The liquid in Titan’s lakes and seas is mostly methane and ethane.
The data were obtained by Cassini’s radar instrument from 2004 to 2013. In this projection, the north pole is at the center. The view extends down to 50 degrees north latitude. In this color scheme, liquids appear blue and black depending on the way the radar bounced off the surface. Land areas appear yellow to white. A haze was added to simulate the Titan atmosphere.
Kraken Mare, Titan’s largest sea, is the body in black and blue that sprawls from just below and to the right of the north pole down to the bottom right. Ligeia Mare, Titan’s second largest sea, is a nearly heart-shaped body to the left and above the north pole. Punga Mare is just below the north pole.
The area above and to the left of the north pole is dotted with smaller lakes. Lakes in this area are about 30 miles (50 kilometers) across or less.
Most of the bodies of liquid on Titan occur in the northern hemisphere. In fact nearly all the lakes and seas on Titan fall into a box covering about 600 by 1,100 miles (900 by 1,800 kilometers). Only 3 percent of the liquid at Titan falls outside of this area.
Scientists are trying to identify the geologic processes that are creating large depressions capable of holding major seas in this limited area. A prime suspect is regional extension of the crust, which on Earth leads to the formation of faults creating alternating basins and roughly parallel mountain ranges. This process has shaped the Basin and Range province of the western United States, and during the period of cooler climate 13,000 years ago much of the present state of Nevada was flooded with Lake Lahontan, which (though smaller) bears a strong resemblance to the region of closely packed seas on Titan.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. NASA’s Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington, DC. The Cassini orbiter was designed, developed and assembled at JPL. The radar instrument was built by JPL and the Italian Space Agency, working with team members from the United States and several European countries.
This artist’s impression shows Jupiter and its moon Europa using actual Jupiter and Europa images in visible light. The Hubble ultraviolet images showing the faint emission from the water vapour plumes have been superimposed, respecting the size but not the brightness of the plumes. Click to Enlarge
NASA’s Hubble Space Telescope has observed water vapor above the frigid south polar region of Jupiter’s moon Europa, providing the first strong evidence of water plumes erupting off the moon’s surface.
Previous scientific findings from other sources already point to the existence of an ocean located under Europa’s icy crust. Researchers are not yet fully certain whether the detected water vapor is generated by erupting water plumes on the surface, but they are confident this is the most likely explanation.
This is an artist’s concept of a plume of water vapor thought to be ejected
off the frigid, icy surface of the Jovian moon Europa, located about
500 million miles (800 million kilometers) from the sun.
Image Credit: NASA/ESA/K. Retherford/SWRI Full image and caption
Should further observations support the finding, this would make Europa the second moon in the solar system known to have water vapor plumes. The findings are being published in the Dec. 12 online issue of Science Express, and reported at the meeting of the American Geophysical Union in San Francisco.
“By far the simplest explanation for this water vapor is that it erupted from plumes on the surface of Europa,” said lead author Lorenz Roth of Southwest Research Institute in San Antonio. “If those plumes are connected with the subsurface water ocean we are confident exists under Europa’s crust, then this means that future investigations can directly investigate the chemical makeup of Europa’s potentially habitable environment without drilling through layers of ice. And that is tremendously exciting.”
In 2005, NASA’s Cassini orbiter detected jets of water vapor and dust spewing off the surface of Saturn’s moon Enceladus. Although ice and dust particles have subsequently been found in the Enceladus plumes, only water vapor gases have been measured at Europa so far.
Hubble spectroscopic observations provided the evidence for Europa plumes in December 2012. Time sampling of Europa’s auroral emissions measured by Hubble’s imaging spectrograph enabled the researchers to distinguish between features created by charged particles from Jupiter’s magnetic bubble and plumes from Europa’s surface, and also to rule out more exotic explanations such as serendipitously observing a rare meteorite impact.
This graphic shows the location of water vapor detected over Europa’s south pole in observations taken by NASA’s Hubble Space Telescope in December 2012.
The imaging spectrograph detected faint ultraviolet light from an aurora, powered by Jupiter’s intense magnetic field, near the moon’s south pole. Excited atomic oxygen and hydrogen produce a variable auroral glow and leave a telltale sign that are the products of water molecules being broken apart by electrons along magnetic field lines.
“We pushed Hubble to its limits to see this very faint emission. These could be stealth plumes, because they might be tenuous and difficult to observe in the visible light,” said Joachim Saur of the University of Cologne, Germany. Saur, who is principal investigator of the Hubble observation campaign, co-wrote the paper with Roth.
Roth suggested that long cracks on Europa’s surface, known as lineae, might be venting water vapor into space. Cassini has seen similar fissures that host the Enceladus jets.
Also the Hubble team found that the intensity of the Europa plumes, like those at Enceladus, varies with Europa’s orbital position. Active jets have only been seen when the moon is farthest from Jupiter. The researchers could not detect any sign of venting when Europa is closer to Jupiter.
One explanation for the variability is that these lineae experience more stress as gravitational tidal forces push and pull on the moon and open vents at larger distances from Jupiter. The vents are narrowed or closed when the moon is closest to the gas-giant planet.
“The apparent plume variability supports a key prediction that Europa should tidally flex by a significant amount if it has a subsurface ocean,” said Kurt Retherford, also of Southwest Research Institute.
The Europa and Enceladus plumes have remarkably similar abundances of water vapor. Because Europa has a roughly 12 times stronger gravitational pull than Enceladus, the minus-40-degree-Fahrenheit (minus-40-degree-Celsius) vapor for the most part doesn’t escape into space as it does at Enceladus, but rather falls back onto the surface after reaching an altitude of 125 miles (201 kilometers), according to the Hubble measurements. This could leave bright surface features near the moon’s south polar region, the researchers hypothesize.
“If confirmed, this new observation once again shows the power of the Hubble Space Telescope to explore and opens a new chapter in our search for potentially habitable environments in our solar system,” said John Grunsfeld, an astronaut who participated Hubble servicing missions and now serves as NASA’s associate administrator for science in Washington. “The effort and risk we took to upgrade and repair Hubble becomes all the more worthwhile when we learn about exciting discoveries like this one from Europa.”
The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute (STScI) conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, Inc., in Washington, D.C.
NASA’s Cassini spacecraft has obtained the highest-resolution movie yet of a unique six-sided jet stream, known as the hexagon, around Saturn’s north pole.
This is the first hexagon movie of its kind, using color filters, and the first to show a complete view of the top of Saturn down to about 70 degrees latitude. Spanning about 20,000 miles (30,000 kilometers) across, the hexagon is a wavy jet stream of 200-mile-per-hour winds (about 322 kilometers per hour) with a massive, rotating storm at the center. There is no weather feature exactly, consistently like this anywhere else in the solar system.
“The hexagon is just a current of air, and weather features out there that share similarities to this are notoriously turbulent and unstable,” said Andrew Ingersoll, a Cassini imaging team member at the California Institute of Technology in Pasadena. “A hurricane on Earth typically lasts a week, but this has been here for decades — and who knows — maybe centuries.”
Weather patterns on Earth are interrupted when they encounter friction from landforms or ice caps. Scientists suspect the stability of the hexagon has something to do with the lack of solid landforms on Saturn, which is essentially a giant ball of gas.