Cassini Spacecraft: Top Discoveries

Our Cassini spacecraft has been exploring Saturn, its stunning rings and its strange and beautiful moons for more than a decade.

Having expended almost every bit of the rocket propellant it carried to Saturn, operators are deliberately plunging Cassini into the planet to ensure Saturn’s moons will remain pristine for future exploration – in particular, the ice-covered, ocean-bearing moon Enceladus, but also Titan, with its intriguing pre-biotic chemistry.

Let’s take a look back at some of Cassini’s top discoveries:  

Titan

Under its shroud of haze, Saturn’s planet-sized moon Titan hides dunes, mountains of water ice and rivers and seas of liquid methane. Of the hundreds of moons in our solar system, Titan is the only one with a dense atmosphere and large liquid reservoirs on its surface, making it in some ways more like a terrestrial planet.

Both Earth and Titan have nitrogen-dominated atmospheres – over 95% nitrogen in Titan’s case. However, unlike Earth, Titan has very little oxygen; the rest of the atmosphere is mostly methane and traced amounts of other gases, including ethane.

There are three large seas, all located close to the moon’s north pole, surrounded by numerous smaller lakes in the northern hemisphere. Just one large lake has been found in the southern hemisphere.

Enceladus

The moon Enceladus conceals a global ocean of salty liquid water beneath its icy surface. Some of that water even shoots out into space, creating an immense plume!

For decades, scientists didn’t know why Enceladus was the brightest world in the solar system, or how it related to Saturn’s E ring. Cassini found that both the fresh coating on its surface, and icy material in the E ring originate from vents connected to a global subsurface saltwater ocean that might host hydrothermal vents.

With its global ocean, unique chemistry and internal heat, Enceladus has become a promising lead in our search for worlds where life could exist.

Iapetus

Saturn’s two-toned moon Iapetus gets its odd coloring from reddish dust in its orbital path that is swept up and lands on the leading face of the moon.

The most unique, and perhaps most remarkable feature discovered on Iapetus in Cassini images is a topographic ridge that coincides almost exactly with the geographic equator. The physical origin of the ridge has yet to be explained…

It is not yet year whether the ridge is a mountain belt that has folded upward, or an extensional crack in the surface through which material from inside Iapetus erupted onto the surface and accumulated locally.

Saturn’s Rings

Saturn’s rings are made of countless particles of ice and dust, which Saturn’s moons push and tug, creating gaps and waves.

Scientists have never before studied the size, temperature, composition and distribution of Saturn’s rings from Saturn obit. Cassini has captured extraordinary ring-moon interactions, observed the lowest ring-temperature ever recorded at Saturn, discovered that the moon Enceladus is the source for Saturn’s E ring, and viewed the rings at equinox when sunlight strikes the rings edge-on, revealing never-before-seen ring features and details.

Cassini also studied features in Saturn’s rings called “spokes,” which can be longer than the diameter of Earth. Scientists think they’re made of thin icy particles that are lifted by an electrostatic charge and only last a few hours.  

Auroras

The powerful magnetic field that permeates Saturn is strange because it lines up with the planet’s poles. But just like Earth’s field, it all creates shimmering auroras.

Auroras on Saturn occur in a process similar to Earth’s northern and southern lights. Particles from the solar wind are channeled by Saturn’s magnetic field toward the planet’s poles, where they interact with electrically charged gas (plasma) in the upper atmosphere and emit light.  

Turbulent Atmosphere

Saturn’s turbulent atmosphere churns with immense storms and a striking, six-sided jet stream near its north pole.

Saturn’s north and south poles are also each beautifully (and violently) decorated by a colossal swirling storm. Cassini got an up-close look at the north polar storm and scientists found that the storm’s eye was about 50 times wider than an Earth hurricane’s eye.

Unlike the Earth hurricanes that are driven by warm ocean waters, Saturn’s polar vortexes aren’t actually hurricanes. They’re hurricane-like though, and even contain lightning. Cassini’s instruments have ‘heard’ lightning ever since entering Saturn orbit in 2004, in the form of radio waves. But it wasn’t until 2009 that Cassini’s cameras captured images of Saturnian lighting for the first time.

Cassini scientists assembled a short video of it, the first video of lightning discharging on a planet other than Earth.

Cassini’s adventure will end soon because it’s almost out of fuel. So to avoid possibly ever contaminating moons like Enceladus or Titan, on Sept. 15 it will intentionally dive into Saturn’s atmosphere.

The spacecraft is expected to lose radio contact with Earth within about one to two minutes after beginning its decent into Saturn’s upper atmosphere. But on the way down, before contact is lost, eight of Cassini’s 12 science instruments will be operating! More details on the spacecraft’s final decent can be found HERE.

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Cassini Mission: What’s Next?

It’s Friday, Sept. 15 and our Cassini mission has officially come to a spectacular end. The final signal from the spacecraft was received here on Earth at 7:55 a.m. EDT after a fateful plunge into Saturn’s atmosphere.

After losing contact with Earth, the spacecraft burned up like a meteor, becoming part of the planet itself.

Although bittersweet, Cassini’s triumphant end is the culmination of a nearly 20-year mission that overflowed with discoveries.

But, what happens now?

Mission Team and Data

Now that the spacecraft is gone, most of the team’s engineers are migrating to other planetary missions, where they will continue to contribute to the work we’re doing to explore our solar system and beyond.

Mission scientists will keep working for the coming years to ensure that we fully understand all of the data acquired during the mission’s Grand Finale. They will carefully calibrate and study all of this data so that it can be entered into the Planetary Data System. From there, it will be accessible to future scientists for years to come.

Even beyond that, the science data will continue to be worked on for decades, possibly more, depending on the research grants that are acquired.

Other team members, some who have spent most of their career working on the Cassini mission, will use this as an opportunity to retire.

Future Missions

In revealing that Enceladus has essentially all the ingredients needed for life, the mission energized a pivot to the exploration of “ocean worlds” that has been sweeping planetary science over the past couple of decades.

Jupiter’s moon Europa has been a prime target for future exploration, and many lessons during Cassini’s mission are being applied in planning our Europa Clipper mission, planned for launch in the 2020s.

The mission will orbit the giant planet, Jupiter, using gravitational assists from large moons to maneuver the spacecraft into repeated close encounters, much as Cassini has used the gravity of Titan to continually shape the spacecraft’s course.

In addition, many engineers and scientists from Cassini are serving on the new Europa Clipper mission and helping to shape its science investigations. For example, several members of the Cassini Ion and Neutral Mass Spectrometer team are developing an extremely sensitive, next-generation version of their instrument for flight on Europa Clipper. What Cassini has learned about flying through the plume of material spraying from Enceladus will be invaluable to Europa Clipper, should plume activity be confirmed on Europa.

In the decades following Cassini, scientists hope to return to the Saturn system to follow up on the mission’s many discoveries. Mission concepts under consideration include robotic explorers to drift on the methane seas of Titan and fly through the Enceladus plume to collect and analyze samples for signs of biology.

Atmospheric probes to all four of the outer planets have long been a priority for the science community, and the most recent recommendations from a group of planetary scientists shows interest in sending such a mission to Saturn. By directly sampling Saturn’s upper atmosphere during its last orbits and final plunge, Cassini is laying the groundwork for an potential Saturn atmospheric probe.

A variety of potential mission concepts are discussed in a recently completed study — including orbiters, flybys and probes that would dive into Uranus’ atmosphere to study its composition. Future missions to the ice giants might explore those worlds using an approach similar to Cassini’s mission.

Learn more about the Cassini mission and its Grand Finale HERE.

Follow the mission on Facebook and Twitter for the latest updates.

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The Day You Were Born

*Note. This is a very minor factor in the human psyche, and not technically a component of the natal chart. Each day of the week has an energy which it imparts to individuals born on it, but it is vague and often a subtle undertone or theme rather than a prominent, overt, direct influence. This is closely related to the “mundane” matters of the 6th house, the everyday aspect of our lives, and how you approach or behave in that area. The planet ruling your day of birth may be interpreted to have increased energy or importance in your natal chart.


SUNDAY || Sun

People born on Sunday tend to have well-defined identities, or at least a strong sense of self, and they deeply value their individuality. They can be very creative individuals, full of vitality and unique personal power, and they’re often well-liked for their radiance. Above all, their opinion of & belief in themselves drives them in their everyday lives. Their actions revolve around independent choice.


MONDAY || Moon

People born on Monday tend to be rather sensitive and emotionally responsive. Their feelings are deep & strong, and typically have a significant influence over their actions. Privacy and comfort are priorities in their everyday lives; they strive to feel safe, and may be reserved. They can be profoundly compassionate. They value their memories, which are usually vivid & clear, and protect their history.


TUESDAY || Mars

People born on Tuesday tend to be energetic and forthright, with a vital intensity and passionate disposition that carries them throughout their everyday lives. Taking action and being decisive are important to them; strength of character, ambition, and progress help define who they are. They enjoy exhilaration and feed off adrenaline, so they could be reckless thrill-seekers if they’re able.


WEDNESDAY || Mercury

People born on Wednesday tend to be thoughtful and inventive. Their minds are central to their identity; the cultivation, communication, and manifestation of ideas is often what their everyday lives revolve around. Exchanges are crucial to their well-being, as conversation is their main avenue of self-expression. They tend to be busy-bodies, focused on a perpetually-flowing daily process.


THURSDAY || Jupiter

People born on Thursday tend to have “big” personalities; they’re often open, expressive, & engaging. Being a part of the world around them is vital to their happiness, & that is what their everyday lives revolve around. The pleasures of life are their hobbies. Their minds & hearts are expansive, giving them grand ideas & grand connectivity. The deeper meaning of things is important to them.


FRIDAY || Venus

People born on Friday tend to be charming & generally likeable. They’re polite, graceful, and easygoing, with rather “breezy” and warm personalities which attract others to them. They have a good sense of style & know how to present themselves in appealing ways. Beauty, indulgence, pleasure, & self-esteem are what their everyday lives revolve around. Their values are important to them.


SATURDAY || Saturn

People born on Saturday tend to have solid, responsible personalities. They are focused, determined, and disciplined. They may be reserved individuals with anxious dispositions or a cool, collected mien typically mistaken for coldness. Their strong, definite ambitions and continuous self-improvement are what their everyday lives revolve around. They are dignified, independent hard-workers.

Planets: As Seen by Voyager

The Voyager 1 and 2 spacecraft explored Jupiter, Saturn, Uranus and Neptune before starting their journey toward interstellar space. Here you’ll find some of those images, including “The Pale Blue Dot” – famously described by Carl Sagan – and what are still the only up-close images of Uranus and Neptune.

These twin spacecraft took some of the very first close-up images of these planets and paved the way for future planetary missions to return, like the Juno spacecraft at Jupiter, Cassini at Saturn and New Horizons at Pluto.

Jupiter

Photography of Jupiter began in January 1979, when images of the brightly banded planet already exceeded the best taken from Earth. They took more than 33,000 pictures of Jupiter and its five major satellites. 

Findings:

  • Erupting volcanoes on Jupiter’s moon Io, which has 100 times the volcanic activity of Earth. 
  • Better understanding of important physical, geological, and atmospheric processes happening in the planet, its satellites and magnetosphere.
  • Jupiter’s turbulent atmosphere with dozens of interacting hurricane-like storm systems.

Saturn

The Saturn encounters occurred nine months apart, in November 1980 and August 1981. The two encounters increased our knowledge and altered our understanding of Saturn. The extended, close-range observations provided high-resolution data far different from the picture assembled during centuries of Earth-based studies.

Findings:

  • Saturn’s atmosphere is almost entirely hydrogen and helium.
  • Subdued contrasts and color differences on Saturn could be a result of more horizontal mixing or less production of localized colors than in Jupiter’s atmosphere.
  • An indication of an ocean beneath the cracked, icy crust of Jupiter’s moon Europa. 
  • Winds blow at high speeds in Saturn. Near the equator, the Voyagers measured winds about 1,100 miles an hour.

Uranus

The Voyager 2 spacecraft flew closely past distant Uranus, the seventh planet from the Sun. At its closest, the spacecraft came within 50,600 miles of Uranus’s cloud tops on Jan. 24, 1986. Voyager 2 radioed thousands of images and voluminous amounts of other scientific data on the planet, its moons, rings, atmosphere, interior and the magnetic environment surrounding Uranus.

Findings:

  • Revealed complex surfaces indicative of varying geologic pasts.
  • Detected 11 previously unseen moons.
  • Uncovered the fine detail of the previously known rings and two newly detected rings.
  • Showed that the planet’s rate of rotation is 17 hours, 14 minutes.
  • Found that the planet’s magnetic field is both large and unusual.
  • Determined that the temperature of the equatorial region, which receives less sunlight over a Uranian year, is nevertheless about the same as that at the poles.

Neptune

Voyager 2 became the first spacecraft to observe the planet Neptune in the summer of 1989. Passing about 3,000 miles above Neptune’s north pole, Voyager 2 made its closest approach to any planet since leaving Earth 12 years ago. Five hours later, Voyager 2 passed about 25,000 miles from Neptune’s largest moon, Triton, the last solid body the spacecraft had the opportunity to study.

Findings: 

  • Discovered Neptune’s Great Dark Spot
  • Found that the planet has strong winds, around 1,000 miles per hour
  • Saw geysers erupting from the polar cap on Neptune’s moon Triton at -390 degrees Fahrenheit

Solar System Portrait

This narrow-angle color image of the Earth, dubbed ‘Pale Blue Dot’, is a part of the first ever ‘portrait’ of the solar system taken by Voyager 1. 

The spacecraft acquired a total of 60 frames for a mosaic of the solar system from a distance of more than 4 billion miles from Earth and about 32 degrees above the ecliptic.

From Voyager’s great distance, Earth is a mere point of light, less than the size of a picture element even in the narrow-angle camera.

“Look again at that dot. That’s here. That’s home. That’s us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives.” - Carl Sagan

Both spacecraft will continue to study ultraviolet sources among the stars, and their fields and particles detectors will continue to search for the boundary between the Sun’s influence and interstellar space. The radioisotope power systems will likely provide enough power for science to continue through 2025, and possibly support engineering data return through the mid-2030s. After that, the two Voyagers will continue to orbit the center of the Milky Way.

Learn more about the Voyager spacecraft HERE.

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