Huygens’ view of the 1st landing on Titan

Ten years ago, ESA’s Huygens probe descended to the surface of Titan, Saturn’s largest moon.

Detection of a strongly negative surface potential at Saturn’s moon Hyperion

 

Illustration showing how a magnetic connection between the spacecraft and Hyperion can lead to the reduction in 18–100 keV electron counts observed by LEMMS. Not to scale

Hyperion is a highly irregular outer moon of Saturn, with dimensions of 180 × 133 × 103  km and a mean radius of 133 ± 8  km. It has a low mean density, indicating that it may consist primarily of water ice with an unusually high degree of porosity (>40%), resulting in its characteristic “sponge-like” appearance. Observations by the Voyager and Cassini spacecraft found that Hyperion has a chaotic spin state, rotating nearly about its long axis by 72–75°/d. Its orbital semimajor axis is 24.55 Saturn radii (1  Rs  =  60,268 km), which takes it outside Saturn’s magnetosphere for parts of its orbit. Hence, Hyperion is exposed to plasma conditions representative of the outer magnetosphere, magnetosheath, or solar wind, depending on its orbital position and the overall magnetospheric configuration at the time.

On 26 September 2005, Cassini conducted its only close targeted flyby of Saturn’s small moon Hyperion. Approximately 6 min before the closest approach, the electron spectrometer (ELS), part of the Cassini Plasma Spectrometer (CAPS) detected a field-aligned electron population originating from the direction of the moon’s surface. Plasma wave activity detected by the Radio and Plasma Wave instrument suggests electron beam activity. A dropout in energetic electrons was observed by both CAPS-ELS and the Magnetospheric Imaging Instrument Low-Energy Magnetospheric Measurement System, indicating that the moon and the spacecraft were magnetically connected when the field-aligned electron population was observed. This constitutes a remote detection of a strongly negative (~ −200 V) surface potential on Hyperion, consistent with the predicted surface potential in regions near the solar terminator.

Celebrating 10 Years Since Titan Landing

Source: NASA

Ten years ago, an observer from Earth parachuted into the haze of an alien moon toward an uncertain fate. After a gentle descent lasting more than two hours, it landed with a thud on a frigid floodplain, surrounded by icy cobblestones. With this feat, the Huygens probe accomplished humanity’s first landing on a moon in the outer solar system. Huygens was safely on Titan, the largest moon of Saturn.

The hardy probe not only survived the descent and landing, but continued to transmit data for more than an hour on the frigid surface of Titan, until its batteries were drained.

Since that historic moment, scientists from around the world have pored over volumes of data about Titan, sent to Earth by Huygens – a project of the European Space Agency – and its mothership, NASA’s Cassini spacecraft. In the past 10 years, data from the dynamic spacecraft duo have revealed many details of a surprisingly Earth-like world.

Tethys the Spy

NASA’s Cassini orbiter shows that Tethys appears to be peeking out from behind Rhea, watching the watcher. Scientists believe that Tethys’ surprisingly high albedo is due to the water ice jets emerging from its neighbor, Enceladus. The fresh water ice becomes the E ring and can eventually arrive at Tethys, giving it a fresh surface layer of clean ice. 

NASA/JPL-Caltech/Space Science Institute

Mimas by Saturnshine

Although we are used to seeing Saturn’s moons lit directly by the Sun, sometimes we can catch them illuminated by “Saturnshine.” Here, we see Mimas (upper right) lit by light reflected off of Saturn. 

NASA/JPL-Caltech/Space Science Institute

Elevated View of Enceladus’ South Pole

This dramatic view looks across the region of Enceladus’ geyser basin and down on the ends of the Baghdad and Damascus fractures that face Saturn. The image, which looks approximately in the direction of Saturn, was taken from a more elevated viewpoint than other Cassini survey images of this area of the moon’s south pole. 

NASA/JPL-Caltech/Space Science Institute

Saturn’s faint D ring

Not all of Saturn’s rings are created equal: here the C and D rings appear side-by-side, but the C ring, which occupies the bottom half of this image, clearly outshines its neighbor. 

NASA/JPL-Caltech/Space Science Institute

Rivers of methane produced surprisingly little erosion on Titan

For many years, Titan's thick, methane- and nitrogen-rich atmosphere kept astronomers from seeing what lies beneath. Saturn's largest moon appeared through telescopes as a hazy orange orb, in contrast to other heavily cratered moons in the solar system.

The atmosphere of Titan is full of a thick haze, so it's impossible to take clear pictures of the surface in the optical wavelengths.

Titan flybys: How gravity assists work

For the past 18 months, NASA’s Cassini spacecraft has been orbiting Saturn in practically the same plane as the one that slices through the planet’s equator. Beginning with the Titan flyby on May 22, navigators started to tilt Cassini’s orbit in order to obtain a different view of the Saturnian system. The measure of the spacecraft orbit’s tilt relative to Saturn’s equator is referred to as its inclination. The recent Titan flyby raised Cassini’s inclination to nearly 16 degrees. Seven more Titan flybys will ultimately raise Cassini’s inclination to nearly 62 degrees by April 2013. On Earth, an orbit with a 62-degree inclination would pass as far north as Alaska and, at its southernmost point, skirt the latitude containing the tip of the Antarctic Peninsula.

It's been nearly two years since NASA's Cassini spacecraft has had views like these of Saturn's rings. These views are possible again because Cassini has changed the angle at which it orbits Saturn and regularly passes above and below Saturn's equatorial plane. Steeply inclined orbits around the Saturn system also allow scientists to get better views of the poles and atmosphere of Saturn and its moons. A group of scientists has restarted the team's studies of propeller-shaped gaps. These gaps are cleared out by objects that are smaller than known moons but larger than typical ring particles. Cassini scientists haven't seen propellers in two years. Because some of the propellers are exactly where models predicted they would be, scientists believe they are seeing some old friends again. Credit: NASA/JPL-Caltech/SSI/Cornell

Tropical lakes on Titan

The existence of oceans or lakes of liquid methane on Saturn's moon Titan was predicted more than 20 years ago. But with a dense haze preventing a closer look it has not been possible to confirm their presence. Until the Cassini flyby of July 22, 2006, that is. Radar imaging data from the flyby, published in the journal Nature, provide convincing evidence for large bodies of liquid. Intensity in this colorized image is proportional to how much radar brightness is returned, or more specifically, the logarithm of the radar backscatter cross-section. The colors are not a representation of what the human eye would see. The lakes, darker than the surrounding terrain, are emphasized here by tinting regions of low backscatter in blue. Radar-brighter regions are shown in tan. Smallest details in this image are about 500 meters (1,640 feet) across. Credit: NASA/JPL-Caltech/USGS

Methone and Tethys

NASA's Cassini spacecraft captured these raw, unprocessed images of Saturn's moons Methone and Tethys on May 20, 2012. With a close-approach distance of about 1,200 miles (1,900 kilometers), this was Cassini's closest flyby of the 2-mile-wide (3-kilometer-wide) Methone.

This raw, unprocessed image of Methone was taken on May 20, 2012 and received on Earth May 21, 2012. The image has not been validated or calibrated. Credit: NASA/JPL-Caltech/SSI