A new long-term study using data from NASA’s Cassini spacecraft has revealed a surprising feature emerging at Saturn’s northern pole as it nears summertime: a warming, high-altitude vortex with a hexagonal shape, akin to the famous hexagon seen deeper down in Saturn’s clouds.
The finding, published Sept. 3 in Nature Communications, is intriguing, because it suggests that the lower-altitude hexagon may influence what happens above, and that it could be a towering structure hundreds of miles in height.
When Cassini arrived at the Saturnian system in 2004, the southern hemisphere was enjoying summertime, while the northern was in the midst of winter. The spacecraft spied a broad, warm high-altitude vortex at Saturn’s southern pole but none at the planet’s northern pole. The new study reports the first glimpses of a northern polar vortex forming high in the atmosphere, as Saturn’s northern hemisphere approached summertime. This warm vortex sits hundreds of miles above the clouds, in the stratosphere, and reveals an unexpected surprise.
“The edges of this newly-found vortex appear to be hexagonal, precisely matching a famous and bizarre hexagonal cloud pattern we see deeper down in Saturn’s atmosphere,” said Leigh Fletcher of the University of Leicester, lead author of the new study.
Saturn’s cloud levels host the majority of the planet’s weather, including the pre-existing north polar hexagon. This feature was discovered by NASA’s Voyager spacecraft in the 1980s and has been studied for decades; a long-lasting wave potentially tied to Saturn’s rotation, it is a type of phenomenon also seen on Earth, as in the Polar Jet Stream.
Its properties were revealed in detail by Cassini, which observed the feature in multiple wavelengths — from the ultraviolet to the infrared — using instruments including its Composite Infrared Spectrometer (CIRS). However, at the start of the mission this instrument could not peer farther up into the northern stratosphere, where temperatures were too cold for reliable CIRS infrared observations, leaving these higher-altitude regions relatively unexplored for many years.
“The mystery and extent of the hexagon continue to grow, even after Cassini’s 13 years in orbit around Saturn,” said Linda Spilker, Cassini project scientist. “I look forward to seeing other new discoveries that remain to be found in the Cassini data.”
Saturn is six planets away from the sun. The second largest planet to share the solar system with Earth is Saturn. The only one that beats it in size is Jupiter. Five planets can be seen from Earth with the naked eye and Saturn is one of them. This includes the Saturn’s rings which span approximately 175,000 miles.
Composition of Saturn’s Rings
When looking at all known solar systems, Saturn’s rings are considered to be the most extensive. They are comprised of countless small particles, which are believed to be pieces of asteroids, comets or shattered moons, that are constantly orbiting the planet. The particles can range from a mere micrometer to larger meter in size. The atmosphere in the area of the rings is an oxygen atmosphere.
Why Saturn’s Rings Are So Bright
The ice particles that cover the elements of the rings are not yet covered in dark dust, giving them a bright appearance against the space sky. The rings are also unstable and rapidly rearranging themselves and experiencing high-speed collisions. This is due to all of the moons on Saturn and their gravitational effects. These forces are also responsible for creating the numerous gaps in the rings that vary in size from very small to quite large.
Groups of Saturn’s Rings
There are four primary groups of saturn’s rings and three additional groups that are narrower and fainter. Divisions are a type of gap that separates the groups of rings. In 1980, it was discovered by the Voyager that thousands of smaller rings make up the seven ring groups.
Since Saturn is a bit closer to Earth, this makes it a little easier to scientists and researchers to get information about the planet. It is known for its rings, but it is also the second largest planet, making it one that certainly dominates the solar system.
A thrilling epoch in the exploration of our solar system came to a close today, as NASA’s Cassini spacecraft made a fateful plunge into the atmosphere of Saturn, ending its 13-year tour of the ringed planet.
“This is the final chapter of an amazing mission, but it’s also a new beginning,” said Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate at NASA Headquarters in Washington. “Cassini’s discovery of ocean worlds at Titan and Enceladus changed everything, shaking our views to the core about surprising places to search for potential life beyond Earth.”
Telemetry received during the plunge indicates that, as expected, Cassini entered Saturn’s atmosphere with its thrusters firing to maintain stability, as it sent back a unique final set of science observations. Loss of contact with the Cassini spacecraft occurred at 7:55 a.m. EDT (4:55 a.m. PDT), with the signal received by NASA’s Deep Space Network antenna complex in Canberra, Australia.
“It’s a bittersweet, but fond, farewell to a mission that leaves behind an incredible wealth of discoveries that have changed our view of Saturn and our solar system, and will continue to shape future missions and research,” said Michael Watkins, director of NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California, which manages the Cassini mission for the agency. JPL also designed, developed and assembled the spacecraft.
Cassini’s plunge brings to a close a series of 22 weekly “Grand Finale” dives between Saturn and its rings, a feat never before attempted by any spacecraft.
“The Cassini operations team did an absolutely stellar job guiding the spacecraft to its noble end,” said Earl Maize, Cassini project manager at JPL. “From designing the trajectory seven years ago, to navigating through the 22 nail-biting plunges between Saturn and its rings, this is a crack shot group of scientists and engineers that scripted a fitting end to a great mission. What a way to go. Truly a blaze of glory.”
As planned, data from eight of Cassini’s science instruments was beamed back to Earth. Mission scientists will examine the spacecraft’s final observations in the coming weeks for new insights about Saturn, including hints about the planet’s formation and evolution, and processes occurring in its atmosphere.
“Things never will be quite the same for those of us on the Cassini team now that the spacecraft is no longer flying,” said Linda Spilker, Cassini project scientist at JPL. “But, we take comfort knowing that every time we look up at Saturn in the night sky, part of Cassini will be there, too.”
Cassini launched in 1997 from Cape Canaveral Air Force Station in Florida and arrived at Saturn in 2004. NASA extended its mission twice – first for two years, and then for seven more. The second mission extension provided dozens of flybys of the planet’s icy moons, using the spacecraft’s remaining rocket propellant along the way. Cassini finished its tour of the Saturn system with its Grand Finale, capped by Friday’s intentional plunge into the planet to ensure Saturn’s moons – particularly Enceladus, with its subsurface ocean and signs of hydrothermal activity – remain pristine for future exploration.
While the Cassini spacecraft is gone, its enormous collection of data about Saturn – the giant planet, its magnetosphere, rings and moons – will continue to yield new discoveries for decades to come.
“Cassini may be gone, but its scientific bounty will keep us occupied for many years,” Spilker said. “We’ve only scratched the surface of what we can learn from the mountain of data it has sent back over its lifetime.”
The 20-year mission is coming to an end later this month when the probe makes its final destructive plunge into Saturn.
As part of its grand finale, Cassini has flown closer to the rings than ever before, first grazing the outermost edges of the rings before taking the risky leap of diving through the gap between the rings and Saturn.
Saturn’s big empty
One of the surprises was that it’s quite empty in this gap. This is very different to when Cassini was bombarded by hundreds of dust particles per second as it moved past the outer rings late last year.
But it meant good news for the mission as this final stage had a better chance for success if there was less material in the way.
During a recent ring dive in August, instead of orientating Cassini so that it flew antenna-first through the gap (offering it more protection), the spacecraft was turned around allowing it to capture a fantastic view of the rings as it dived past.
Know your ring ABCs
Over the centuries, as Saturn’s rings have been observed in finer detail, they have been broken into discrete sections. They are named alphabetically in order of discovery, which means from innermost to outermost the order is D, C, B, A, F, G and E.
Saturn’s innermost ring D is much less dense and therefore fainter than its neighbouring ring C.
By comparing new Cassini images of the D ring with its original discovery image from Voyager in 1980, it’s possible to see changes in the ring over a relatively short period of time.
In the Voyager image, three relatively bright arcs can be seen in the D ring (the bright arc in the lower left of frame is the C ring). Most dramatically, the central and brightest arc has faded markedly and moved 200km closer to Saturn (the arc no longer lines up with the Voyager image).
Origin of the rings
We know that the rings are mostly made of water ice, but it’s not clear how they formed or even how old they are.
The fact that they are still bright, rather than coated in dust, suggests a young age – perhaps just 100 million years old, placing their formation in the time of the dinosaurs.
This is consistent with Cassini data, but this theory also presents a problem: it means that a previous collection of moons had a fairly recent and mighty smash-up, creating the rings and five of Saturn’s current-day moons.
Alternatively, Cassini has also shown that there is a lot less dust entering the Saturn system than was originally expected. This makes it possible for the rings to be both ancient and bright, having formed early in the life of the Solar System. Furthermore, interactions within the rings might dust them off and keep them looking young.
Finger on the source
For Saturn’s outermost E ring the source is pretty clear. The moon Enceladus orbits within this ring and Cassini observations have directly traced features in the ring back to geysers erupting from Enceladus’s surface.
Prometheus interacts with the ring once every orbit, when it reaches the point that takes it furthest away from Saturn and closest to the F ring. As Prometheus orbits faster than the ring material, a new streamer is created that is ahead of the old one with every orbit.
Several of Saturn’s smaller moons reside within and carve out gaps in the rings, and Cassini has shown them to have bulges around their middles.
The moon Pan was responsible for clearing the A ring’s large Encke Gap. As it collects the ring material, Pan’s gravity is not strong enough to spread the accumulated matter across its surface, and instead a striking ridge develops.
The tiny moon Daphnis is one of seven moons newly discovered by Cassini. It is just 8km across and as it orbits inside the A ring’s small Keeler Gap, it pulls on the ring particles leaving waves in its wake.
Turning rings into moons
The newly formed object is probably less than a kilometre across but being able to see such a process in action was a complete surprise for Cassini scientists.
It supports the theory that long ago, Saturn’s rings could have been much more massive and capable of producing some of the moons that exist today.
It also potentially provides insight into how the planets of the solar system formed, emerging out of the accretion disk that once orbited the young Sun.
Cassini has certainly achieved its mission objectives to explore Saturn, its atmosphere, magnetosphere and rings and to study Saturn’s moons, particularly Titan. So much has been learned, including the ability to gaze with wonder and awe at the amazing Solar System we are part of.
The Cassini space probe mission is coming to an end this month when the probe makes its final destructive plunge in to Saturn. It’s spent the past thirteen years studying the planet, its rings and moons in unprecedented detail.
Cassini wasn’t the first NASA probe to study Saturn close-up. Pioneer 11 (1979), Voyager 1 (1980) and Voyager 2 (1981) had flown by Saturn earlier, not stopping but giving us the opportunity to see the planet as the amazing world that it is.
But to really understand a planet, you need to spend time with it and that’s what Cassini has done.
Launched in 1997, it took almost seven years to reach Saturn, entering orbit on July 1, 2004. On Christmas Day that year, the Huygens probe was released towards Titan, the first probe ever to land on an object in the outer Solar System.
Cassini was on a four year mission to explore Saturn, its atmosphere, magnetosphere, rings and to study Saturn’s moons, especially Titan the only moon in the Solar System to have a substantial atmosphere.
Time goes by and seasons change
But four years has quickly grown into 13 impressive years, allowing Cassini to watch the slow progression of Saturn’s changing seasons.
When the spacecraft arrived, Saturn’s northern hemisphere was in the dark of winter.
The northern part of Saturn was a mesmerising blue. Less sunlight, particularly the Sun’s harsh ultraviolet rays, could reach the north leaving the atmosphere clear of smog and giving rise to the beautiful blue scattered light.
In August 2009, Cassini had the opportunity to view Saturn at equinox, a special time when the Sun sits directly in line with the planet’s rings. The only light hitting the rings is reflected light from Saturn itself.
During this time shadows were seen dancing across the rings. On average, the rings are very thin, just ten metres or so in thickness, and each of the rings and gaps in the rings have a special name.
At the edge of Saturn’s B ring, the equinox shadows revealed structures that towered as high as 2.5 kilometres. Quite possibly, small moonlets are splashing the ring particles about and forcing them upwards as the moonlets pass by.
As Cassini’s mission comes to an end, summer has arrived at Saturn’s north. The colours are changing and right at the top of Saturn’s north pole, it’s possible to see the distinctive hexagon – a six-sided weather pattern that is now bathed in sunlight.
Embedded in the heart of the hexagon is a roaring hurricane, 50 times larger than any hurricane experienced on Earth. Simulations suggest that it is produced by a jet stream curving around Saturn’s north pole and being jostled about as it interacts with other air currents.
Whatever established the hexagon, it’s certainly long-lived. The pattern was first recorded by the Voyager spacecraft in 1980, although it was not discovered in the data until eight years later.
Pink dancing lights
The Hubble Space Telescope has captured strong aurora on Saturn at ultraviolet wavelengths. But for the first time, Cassini has shown us Saturn’s northern and southern lights shimmering above the planet in visible light.
Unlike Earth’s aurora which are predominantly green and blue due to the oxygen and nitrogen in our atmosphere, Saturn’s aurora vary from pink to purple as charged particles collide and excite the hydrogen-rich atmosphere.
Scientists pay tribute to Cassini
It has involved 17 countries, 260 scientists plus thousands more who worked to design, build and launch the spacecraft.
Team members who have spent their careers working on the Cassini mission reflect on the epic journey. So farewell Cassini, what an amazing time it’s been.
Coming soon I’ll take a closer look at Cassini’s observations of many of the known moon’s of Saturn as well as the space probe’s new discoveries.
NASA scientists have definitively detected the chemical acrylonitrile in the atmosphere of Saturn’s moon Titan, a place that has long intrigued scientists investigating the chemical precursors of life.
On Earth, acrylonitrile, also known as vinyl cyanide, is useful in the manufacture of plastics. Under the harsh conditions of Saturn’s largest moon, this chemical is thought to be capable of forming stable, flexible structures similar to cell membranes. Other researchers have previously suggested that acrylonitrile is an ingredient of Titan’s atmosphere, but they did not report an unambiguous detection of the chemical in the smorgasbord of organic, or carbon-rich, molecules found there.
Now, NASA researchers have identified the chemical fingerprint of acrylonitrile in Titan data collected by the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile. The team found large quantities of the chemical on Titan, most likely in the stratosphere — the hazy part of the atmosphere that gives this moon its brownish-orange color.
“We found convincing evidence that acrylonitrile is present in Titan’s atmosphere, and we think a significant supply of this raw material reaches the surface,” said Maureen Palmer, a researcher with the Goddard Center for Astrobiology at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and lead author of a July 28, 2017, paper in Science Advances.
The cells of Earth’s plants and animals would not hold up well on Titan, where surface temperatures average minus 290 degrees Fahrenheit (minus 179 degrees Celsius), and lakes brim with liquid methane.
In 2015, university scientists tackled the question of whether any organic molecules likely to be on Titan could, under such inhospitable conditions, form structures similar to the lipid bilayers of living cells on Earth. Thin and flexible, the lipid bilayer is the main component of the cell membrane, which separates the inside of a cell from the outside world. This team identified acrylonitrile as the best candidate.
Those researchers proposed that acrylonitrile molecules could come together as a sheet of material similar to a cell membrane. The sheet could form a hollow, microscopic sphere that they dubbed an “azotosome.” This sphere could serve as a tiny storage and transport container, much like the spheres that lipid bilayers can form.
“The ability to form a stable membrane to separate the internal environment from the external one is important because it provides a means to contain chemicals long enough to allow them to interact,” said Michael Mumma, director of the Goddard Center for Astrobiology, which is funded by the NASA Astrobiology Institute. “If membrane-like structures could be formed by vinyl cyanide, it would be an important step on the pathway to life on Saturn’s moon Titan.”
The Goddard team determined that acrylonitrile is plentiful in Titan’s atmosphere, present at concentrations up to 2.8 parts per billion. The chemical is probably most abundant in the stratosphere, at altitudes of at least 125 miles (200 kilometers). Eventually, acrylonitrile makes its way to the cold lower atmosphere, where it condenses and rains out onto the surface.
The researchers calculated how much material could be deposited in Ligeia Mare, Titan’s second-largest lake, which occupies roughly the same surface area as Earth’s Lake Huron and Lake Michigan together. Over the lifetime of Titan, the team estimated, Ligeia Mare could have accumulated enough acrylonitrile to form about 10 million azotosomes in every milliliter, or quarter-teaspoon, of liquid. That’s compared to roughly a million bacteria per milliliter of coastal ocean water on Earth.
The key to detecting Titan’s acrylonitrile was to combine 11 high-resolution data sets from ALMA. The team retrieved them from an archive of observations originally intended to calibrate the amount of light being received by the telescope array.
In the combined data set, Palmer and her colleagues identified three spectral lines that match the acrylonitrile fingerprint. This finding comes a decade after other researchers inferred the presence of acrylonitrile from observations made by the mass spectrometer on NASA’s Cassini spacecraft.
“The detection of this elusive, astrobiologically relevant chemical is exciting for scientists who are eager to determine if life could develop on icy worlds such as Titan,” said Goddard scientist Martin Cordiner, senior author on the paper. “This finding adds an important piece to our understanding of the chemical complexity of the solar system.”
Originally published at NASA
How chemical reactions on a lifeless planet floating around in the cold darkness of space can suddenly give rise to living organisms is one of the biggest questions in science. We don’t even know whether the molecular building blocks of life on Earth were created here or whether they were brought here by comets and meteorites.
Using data from the NASA/ESA Cassini mission, we have now discovered molecules on Saturn’s largest moon Titan which we think drive the production of complex organic compounds. These are molecules that have never been seen in our solar system before. The discovery not only makes Titan a great contender for hosting some sort of primitive life, it also makes it the ideal place to study how life may have arisen from chemical reactions on our own planet.
The molecular building blocks of life are organic compounds including amino acids that can be assembled into proteins, RNA and DNA in living cells. To date, scientists have found these compounds in meteorites, comets and interstellar dust. But the problem is that these materials formed millions of years ago, which means we have no way of knowing how they were created.
Excitingly, it seems these compounds are being created on Titan today. Sunlight and energetic particles from Saturn’s magnetosphere drive reactions in the moon’s upper atmosphere, which is dominated by nitrogen, methane and hydrogen. These lead to larger organic compounds which drift downwards to form the moon’s characteristic “haze” and the extensive dunes – eventually reaching the surface.
To make these surprising discoveries, published in the Astrophysical Journal Letters, the Cassini spacecraft dipped through Titan’s upper atmosphere. Using data beamed back to Earth, we identified the presence of negatively charged molecules called “carbon chain anions”. These appear to “seed” the larger organic compounds observed at the moon – such as polyaromatic hydrocarbons and cyanopolynnes – which could serve as key ingredients for early forms of life. Laboratory experiments have also shown that amino acids could exist there, but the instruments on Cassini are not equipped to detect them.
Negatively charged molecules like these are rare in space environments as they want to react and combine with other molecules – meaning they can be quickly lost. When present, however, they appear to be a crucial “missing link” between simple molecules and complex organic compounds.
So could life currently exist on Titan? It’s not impossible. Water plumes erupting from another of Saturn’s moons, Enceladus, provides a key source of oxygen, which rains down onto Titan’s upper atmosphere. Titan has even been judged the most likely place beyond the Earth to host life by the Planetary habitability index. But life there would likely be quite primitive due to the cold conditions. The presence of liquid methane and ethane seas also means potential organisms would have to function quite differently to those on Earth.
Tracing life on Earth
Remarkably, similar processes are observed in vast molecular clouds beyond our solar system, where stars are born. After the first stars in the universe entered their death throes and fused together heavier elements, rich organic chemistry took place. In these environments, negatively charged molecules have been shown to act as a catalyst for the formation of larger organics, which could then be transferred to solar systems and comets forming from the cloud.
Complex interstellar chemistry has led to the theory that the building blocks of life could have been delivered to Earth from comets which once formed in these molecular clouds. ESA’s Rosetta mission detected the amino acid glycine when visiting Comet 67P/Churymov-Gerasimenko. However, the new discovery makes it entirely possible that the process of creating life from simple molecules took place on Earth instead.
Titan’s dense nitrogen and methane atmosphere is similar to the early Earth’s, some 2.5-4 billion years ago. At this time, before the build-up of oxygen occurred, large quantities of methane resulted in organic chemistry similar to that observed at Titan today. The moon is therefore a high priority target in the search for the beginnings of life.
By making long-term, detailed observations of Titan, we may one day be able to trace the journey from small to large chemical species in order to understand how complex organic molecules are produced. Perhaps we may even be able catch the sudden change from complex organic molecules to living organisms. Follow-up observations of Titan’s atmosphere are already underway using powerful ground-based telescopes such as ALMA. Further missions to explore Titan are also in the works – it is crucial that these are equipped to detect the signatures of life.
The fact that we now see the same chemistry occurring at Titan as in molecular clouds is fascinating, as it indicates the universal nature of these processes. The question now is, could this also be happening within other atmospheres rich in nitrogen and methane, such as at Pluto or Neptune’s moon Triton? What about the thousands of exoplanets discovered in recent years, circling nearby stars?
The concept of a universal pathway towards the building blocks of life has implications for what we need to look for in the onward search for life in the universe. If we detect the molecules just seen on Titan in another environment, we would know that much larger organics and therefore amino acids are likely to exist there.
Future missions, such as NASA’s James Webb Space Telescope and ESA’s exoplanet mission Plato, are set to further study these processes within our solar system and at planets orbiting nearby stars. The UK is even planning its own exoplanet mission, Twinkle, which will also search for signatures of organic molecules.
Although we haven’t detected life itself, the presence of complex organic molecules at Titan, comets and within the interstellar medium means we are certainly coming close to finding its beginnings. And it’s all thanks to Cassini’s near 20-year exploratory journey. So spare a thought for this magnificent spacecraft as it ends its mission in September with a final death-plunge into Saturn’s atmosphere.
A false-color view of Saturn’s rings as the Cassini spacecraft stares towards the horizon. You can see Saturn’s stratosphere in this image as a thin haze that vanishes towards the left side of the frame.
This image composite was created using red, green, and ultraviolet spectral filters. They were obtained by the Cassini spacecraft narrow-angle camera on July 16, 2017, at a distance of about 777,000 miles (1.25 million kilometers) from Saturn. The scale of the image you are seeing is 4 miles (7 kilometers) per pixel on Saturn.
On Sept. 15, 2017 Cassini will pass through the upper atmosphere of saturn in the final five orbits of its mission – before making a final descent into the planet on the 15th. Cassini will fly through the stratosphere (directly above the haze seen in the image) and is expected to lost contact before it completes the journey through said haze.
Cassini, is operated in part by NASA, ESA (the European Space Agency) and the Italian Space Agency. It is managed by The Jet Propulsion Laboratory, a division of Caltech in Pasadena.
Saturn has an incredible abundance of moons and moonlets. It’s largest moon, Titan, is bigger than both Mercury and Pluto. Titan was the first moon identified in it’s orbit by Christiaan Huygens in 1665.
Like here on Earth, Saturn’s moons provide gravitational support. Moons known as “shepherd moons” keep Saturn’s ring in orbit due to their gravitational pull. Small gaps that you see in the rings are caused by moons and moonlets orbiting through it’s path.
Facts about Saturn’s Moons
- Titan is so massive that it effects the orbits of other near-by moons
- Iapetus has a bi-polar atmosphere, one side is covered in snow, the other side is dark and black
- Mimas has an enormour crater on one side that looks like the death star
- Phoebe and other recently discovered moons orbit the planet in the reverse direction
- Pan orbits within the main rings and regularly performs sweepings material out of their orbit, this is known as the Encke gap
- Enceladus contains active ice volcanoes
- Sixteen of Saturn’s moons are tidally locked with one face to the planet at all times
- Hyperion has an odd flattened shape and erratic orbit caused by a recent collision
Names of Saturn’s Moons
Saturn’s confirmed moons: SATURN’S MOONS Aegaeon, Aegir, Albiorix, Anthe, Atlas, Bebhionn, Bergelmir, Bestla, Calypso, Daphnis, Dione, Enceladus, Epimetheus, Erriapus, Farbauti, Fenrir, Fornjot, Greip, Hati, Helene, Hyperion, Hyrrokkin, Iapetus, Ijiraq, Janus, Jarnsaxa, Kari, Kiviuq, Loge, Methone, Mimas, Mundilfari, Narvi, Paaliaq, Pallene, Pan, Pandora, Phoebe, Polydeuces, Prometheus, Rhea, Siarnaq, Skathi, Skoll, Surtur, Suttungr, Tarqeq, Tarvos, Telesto, Tethys, Thrymr, Titan, Ymir
Saturn’s provisional moons: S/2004 S7, S/2004 S12, S/2004 S13, S/2004 S17, S/2006 S1
Distance to Saturn
Saturn’s moons orbit at near-by and wildly exotic distances from the planet. Pan is the closest moon to the planet at 130,000 kilometers (83,000 mies) while Phoebe and other smaller moons orbit as far away as 4,000,000 kilometers (2,485,000 miles).
Elon Musk, the founder of SpaceX and Tesla, has released new details of his vision to colonise parts of the solar system, including Mars, Jupiter’s moon Europa and Saturn’s moon Enceladus. His gung ho plans – designed to make humans a multi-planetary species in case civilisation collapses – include launching flights to Mars as early as 2023.
The details, just published in the journal New Space, are certainly ambitious. But are they realistic? As someone who works on solar system exploration, and the European Space Agency’s new Mars rover in particular, I find them incredible in several ways.
First of all, let’s not dismiss Musk as a Silicon Valley daydreamer. He has had tremendous success with rocket launches to space already. His paper proposes several interesting ways of trying to get to Mars and beyond – and he aims to build a “self-sustaining city” on the red planet.
The idea depends on getting cheaper access to space – the paper says the cost of trips to Mars must be lowered by “five million percent”. An important part of this will be reusable space technology. This is an excellent idea that Musk is already putting into practice with impressive landings of rocket stages back on Earth – undoubtedly a huge technological step.
Making fuel on Mars and stations beyond it is something he also proposes, to make the costs feasible. Experiments towards this are underway, demonstrating that choosing the right propellant is key. The MOXIE experiment on the NASA 2020 rover will investigate whether we can produce oxygen from atmospheric CO2 on Mars. This may be possible. But Musk would like to make methane as well – it would be cheaper and more reusable. This is a tricky reaction which requires a lot of energy.
Yet, so far, it’s all fairly doable. But the plans then get more and more incredible. Musk wants to launch enormous spaceships into orbit around Earth where they will be refuelled several times using boosters launched from the ground while waiting to head to Mars. Each will be designed to take 100 people and Musk wants to launch 1,000 such ships in the space of 40 to 100 years, enabling a million people to leave Earth.
There would also be interplanetary fuel-filling stations on bodies such as Enceladus, Europa and even Saturn’s moon Titan, where there may have been, or may still be, life. Fuel would be produced and stored on these moons. The aim of these would be to enable us to travel deeper into space to places such as the Kuiper belt and the Oort cloud.
The “Red Dragon” capsule is proposed as a potential lander on such missions, using propulsion in combination with other technology rather than parachutes as most Mars missions do. Musk plans to test such a landing on Mars in 2020 with an unmanned mission. But it’s unclear whether it’s doable and the fuel requirements are huge.
Pie in the sky?
There are three hugely important things that Musk misses or dismisses in the paper. Missions such as the ExoMars 2020 rover – and plans to return samples to Earth – will search for signs of life on Mars. And we must await the results before potentially contaminating Mars with humans and their waste. Planetary bodies are covered by “planetary protection” rules to avoid contamination and it’s important for science that all future missions follow them.
Another problem is that Musk dismisses one of the main technical challenges of being on the Martian surface: the temperature. In just two sentences he concludes:
It is a little cold, but we can warm it up. It has a very helpful atmosphere, which, being primarily CO2 with some nitrogen and argon and a few other trace elements, means that we can grow plants on Mars just by compressing the atmosphere.
In reality, the temperature on Mars drops from about 0°C during the day to nearly -120°C at night. Operating in such low temperatures is already extremely difficult for small landers and rovers. In fact, it is an issue that has been solved with heaters in the design for the 300kg ExoMars 2020 rover – but the amount of power required would likely be a show-stopper for a “self-sustaining city”.
Musk doesn’t give any details for how to warm the planet up or compress the atmosphere – each of which are enormous engineering challenges. Previously, science fiction writers have suggested “terraforming” – possibly involving melting its icecaps. This is not only changing the environment forever but would also be challenging in that there is no magnetic field on Mars to help retain the new atmosphere that such manipulation would create. Mars has been losing its atmosphere gradually for 3.8 billion years – which means it would be hard to keep any such warmed-up atmosphere from escaping into space.
The final major problem is that there is no mention of radiation beyond Earth’s magnetic cocoon. The journey to and life on Mars would be vulnerable to potentially fatal cosmic rays from our galaxy and from solar flares. Forecasting for solar flares is in its infancy. With current shielding technology, just a round-trip manned mission to Mars would expose the astronauts to up to four times the advised career limits for astronauts of radiation. It could also harm unmanned spacecraft. Work is underway on predicting space weather and developing better shielding. This would mitigate some of the problems – but we are not there yet.
For missions further afield, there are also questions about temperature and radiation in using Europa and Enceladus as filling stations – with no proper engineering studies assessing them. These moons are bathed in the strongest radiation belts in the solar system. What’s more, I’d question whether it is helpful to see these exciting scientific targets, arguably even more likely than Mars to host current life, as “propellant depots”.
The plans for going further to the Kuiper belt and Oort cloud with humans is firmly in the science fiction arena – it is simply too far and we have no infrastructure. In fact, if Musk really wants to create a new home for humans, the moon may be his best bet – it’s closer after all, which would make it much cheaper.
That said, aiming high usually means we will achieve something – and Musk’s latest plans may help pave the way for later exploration.
The mapping of our solar systems is a complex process involving mathematics and measurements of time. The vastness of our universe is truly amazing and scientists are continually discovering and learning about both the systems beyond our Milky Way and about the planets closest to home.
When researching our neighbor (three planets over), there are some interesting comparisons between Earth and Saturn. Calculating the distance between our two planets varies depending on the day – meaning the distance between them are in constant flux. This is due to the orbital path of the planets in relation to the sun. Simply put, Saturn is 1.2 billion km away from Earth at the closest orbital point, and 1.67 billion km away at the furthest point.
In terms of planet comparisons between Earth and Saturn, “the equatorial diameter of Saturn is 120,536 km; that’s about 9.5 times bigger than the diameter of the Earth. The surface area of Saturn is 83 times the area of Earth, and the volume is 764 times the volume of Earth. In other words, you could fit 764 planets the size of Earth inside Saturn. Finally, the mass of Saturn is 95 times the mass of the Earth.”
However, even with its massive size compared to our planet, Earth is far denser than Saturn – with Earth being a massive 8 times denser.
Saturn is not a planet that could support life; with its gaseous make up and inhabitable environment, scientists do not believe life could survive on this planet. However, scientists have discovered that one of Saturn’s 60 moons, Enceladus, has produced ice geysers. These ice geysers are a key discovery indicating that this moon has water and some ability to keep warm. With this finding, it is theorized that this moon may support some type of life or have the ability to have life exist on its surface.
As Cassini gets closer to Saturn, it keeps bringing us amazing and never before seen imagery. Most of the images are un-processed and shown to the public as un-processed imagery – but thanks to the work of two talented astronomers, astrophysicists Sophia Nasr and graphic designer Jason Majo – we’ve just received our first true color image of Saturn’s North Pole.
Below you can see the center of the North Pole is actually a gorgeous blue that spans 1,200 miles across (2,000kms) surrounded by a subtle shade of yellow.
— Sophia Nasr (@Pharaoness) April 29, 2017
— Jason Major (@JPMajor) April 28, 2017
Saturn’s north pole is also known as as ‘Saturn’s Hexagon’. The hexagon is a turbulent jet stream that was first spotted by Voyager in the 80s.
Clouds swirl around the hexagon at over 300 miles per hour which help to scatter the sunlight to produce the blue-ish color seen in the vortex. In order to produce the image Nasr used Photoshop and combined three images using red, blue, and green filters. This process is the one of closest resemblances we can get next to actually being there.
As Cassini continues to get closer to Saturn, there’s sure to be more amazing imagery, and we promise to keep you updated.
CAPE CANAVERAL, Fla. (Reuters) – NASA’s Cassini spacecraft sent the closest-ever images of Saturn on Thursday after surviving its first plunge inside the planet’s rings, the U.S. space agency said.
A stream of pictures showing Saturn’s swirling clouds, massive hurricane and odd six-sided vortex weather system were transmitted back to Earth by Cassini, which has been exploring Saturn for 13 years.
Now in its final laps around Saturn, Cassini dove through the narrow gap between the planet and its innermost ring on Wednesday, where no spacecraft has ever gone before. It was the first of 22 planned close encounters to bring the robotic probe into unexplored territory between Saturn’s cloud tops and its rings.
“Cassini spacecraft has once again blazed a trail, showing us new wonders and demonstrating where our curiosity can take us if we dare,” National Aeronautics and Space Administration planetary sciences chief Jim Green said in a statement.
Cassini is expected to photograph several small inner moons and study the planet’s winds, clouds, auroras and gravity. The information could help scientists find the source of Saturn’s magnetic field, determine how fast the gas giant rotates and figure out what lies beneath its layers of clouds.
NASA officials are not certain Cassini will survive all its ring dives. The gap between Saturn and the rings is about 1,500 miles (2,400 km) wide and likely littered with ice particles.
Cassini is traveling through the gap at a relative speed of about some 77,000 mph (124,000 kph) so even small particles striking the spacecraft can be deadly.
To protect itself, Cassini’s dish-shaped communications antenna was temporarily repositioned to serve as a shield. The spacecraft will make similar maneuvers during its subsequent dives, the next of which is scheduled for Tuesday.
On its final dive on Sept. 15, Cassini is slated to destroy itself by flying directly into Saturn’s crushing atmosphere.
During its first pass inside the rings, Cassini came within about 1,900 miles (3,000 km) from the top of Saturn’s clouds and within 200 miles (300 km) of its innermost ring.
Cassini has been probing Saturn, the sixth planet from the sun, and its entourage of 62 known moons since July 2004, but is running low on fuel.
NASA plans to crash the spacecraft into Saturn to avoid any chance Cassini could someday collide with any ocean-bearing moons that have the potential to support indigenous microbial life.
(Reporting by Irene Klotz; Editing by Letitia Stein and Jonathan Oatis)
CAPE CANAVERAL, Fla. (Reuters) – NASA’s Cassini spacecraft soared past Saturn’s biggest moon for the last time on Saturday, tapping its gravity to slingshot into a series of exploratory dives inside the planet’s rings, followed by a final fatal plunge into the gas giant.
After nearly 20 years of traveling in space, Cassini used the gravitational tug of Titan, a moon resembling primordial Earth, to hurl itself into a new orbit that will pass through an unexplored region between Saturn’s cloud tops and its rings.
The spacecraft is expected to make the first of 22 dives between the planet and its rings on Wednesday. During the last dive on Sept. 15, Cassini is slated to destroy itself by flying directly into Saturn’s crushing atmosphere.
Cassini’s final run was set into motion early on Saturday by its 127th and final pass by Titan, the U.S. National Aeronautics and Space Administration said.
At its closest approach, NASA projections had Cassini flying 608 miles (979 km) above Titan, zipping by at a relative speed of 13,000 miles per hour (21,000 km per hour).
“Titan’s gravity will bend Cassini’s orbit around Saturn, shrinking it slightly, so that instead of passing just outside the rings, the spacecraft will begin its finale dives which pass just inside the rings,” NASA said in a statement on Wednesday.
During the dives, Cassini will measure how much ice and other materials are in the rings and determine their chemical composition. That information will help scientists learn how the rings formed.
Cassini also will study Saturn’s atmosphere and take measurements to determine the size of the planet’s rocky core.
Cassini has been probing Saturn, the sixth planet from the sun, and its entourage of 62 known moons since July 2004, but is running low on fuel.
NASA plans to crash the spacecraft into Saturn to avoid any chance Cassini could someday collide with Titan, the ocean-bearing moon Enceladus or any other moon that has the potential to support indigenous microbial life.
By destroying the spacecraft, NASA will ensure that any hitchhiking Earth microbes still alive on Cassini will not contaminate the moons for future study.
(Reporting by Irene Klotz; Editing by Letitia Stein and Jonathan Oatis)
(Reuters) – Ice plumes shooting into space from Saturn’s ocean-bearing moon Enceladus contain hydrogen from hydrothermal vents, an environment that some scientists believe led to the rise of life on Earth, research published on Thursday showed.
The discovery makes Enceladus the only place beyond Earth where scientists have found direct evidence of a possible energy source for life, according to the findings in the journal Science.
Similar conditions, in which hot rocks meet ocean water, may have been the cradle for the appearance of microbial life on Earth more than 4 billion years ago.
“If correct, this observation has fundamental implications for the possibility of life on Enceladus,” geochemist Jeffrey Seewald, of the Woods Hole Oceanographic Institution in Massachusetts, wrote in a related commentary in Science.
The discovery was made using NASA’s Cassini spacecraft, which in September will end a 13-year mission exploring Saturn and its entourage of 62 known moons.
The detection of molecular hydrogen occurred in October 2015 during Cassini’s last pass through Enceladus’ plumes, when it skimmed 30 miles (49 km) above the moon’s southern pole taking samples.
In 2005, Cassini discovered Enceladus’s geysers, which shoot hundreds of miles into space. Some of the material falls back onto the surface as a fresh coat of ice, while much of the rest gathers into a halo of ice dust that feeds one of Saturn’s rings.
A decade later, scientists measuring the moon’s slightly wobbly orbit around Saturn determined it holds a vast ocean buried 19- to 25 miles (30- to 40 km) beneath its icy shell. The ocean is believed to be the geysers’ source.
Several moons orbiting Jupiter and Saturn are known to contain underground oceans, but Enceladus is the only one where scientists have found proof of an energy source for life.
“We’re moving toward Enceladus’s ocean being habitable, but we’re not making any claims at this point about it being inhabited,” lead author Hunter Waite, with the Southwest Research Institute in San Antonio, Texas, said in an interview.
“The next time we go back … you’re going to take something that not only picks up on the habitability story, but it starts looking for evidence for life.”
Enceladus has a diameter of 310 miles (500 km) and is one of Saturn’s innermost moons. The heat needed to keep its ocean from freezing is thought to come from tidal forces exerted by Saturn and a neighboring larger moon, Dione.
NASA’s Cassini spacecraft discovered hydrogen in the plume of gas and icy particles spraying from Saturn’s moon Enceladus. The discovery means the small, icy moon — which has a global ocean under its surface — has a source of chemical energy that could be useful for microbes, if any exist there. The finding also provides further evidence that warm, mineral-laden water is pouring into the ocean from vents in the seafloor. On Earth, such hydrothermal vents support thriving communities of life in complete isolation from sunlight. Enceladus now appears likely to have all three of the ingredients scientists think life needs: liquid water, a source of energy (like sunlight or chemical energy), and the right chemical ingredients (like carbon, hydrogen, nitrogen, oxygen).
Cassini is not able to detect life, and has found no evidence that Enceladus is inhabited. But if life is there, that means life is probably common throughout the cosmos; if life has not evolved there, it would suggest life is probably more complicated or unlikely than we have thought. Either way the implications are profound. Future missions to this icy moon may shed light on its habitability.
(Reuters) – NASA is preparing to send its long-lived Cassini probe into the unexplored region between Saturn and its rings for a scientific grand finale before the spacecraft’s suicidal plunge into the planet, space officials said on Tuesday.
Since arriving at Saturn in July 2004, Cassini has been exploring the giant planet and its entourage of 62 known moons, including enigmatic Titan, believed by scientists to resemble an early Earth, and the ocean-bearing moon Enceladus, which is shooting ice particles out into space.
To avoid any chance that hitchhiking Earth microbes still alive on Cassini could contaminate any potential living organisms on Enceladus, NASA plans to crash the spacecraft, which is running out of fuel, into Saturn on Sept. 15.
But before its demise, Cassini has one last mission. On April 22, Cassini will make a final pass by Titan and use the moon’s gravity to slingshot itself into a new orbit that passes inside the 1,200-mile (1,930-km) wide gap between the edge of Saturn’s atmosphere and its inner-most rings.
NASA is hoping Cassini will survive long enough for 22 dives inside the rings, revealing details about the their age and composition. But if a ring particle hits Cassini, it could bring the mission to an premature end because the spacecraft will be traveling at more than 70,000 miles per hour (112,654 kph).
“At those speeds, even a tiny particle can do damage,” Cassini flight engineer Joan Stupik, with NASA’s Jet Propulsion Laboratory in Pasadena, California, told reporters during a news conference on NASA TV.
Scientists hope to learn if the rings are as old as Saturn itself — roughly 4.6 billion years of age — or if they formed later after a passing comet or moon was shredded by the planet’s tremendous gravity.
During the close ring encounters, Cassini also will study Saturn’s atmosphere and take measurements to determine the size of the rocky core believed to exist at the center of the gigantic ball of gas that accounts for most of its size.
However long Cassini lasts, “the grand finale will be spectacular,” said project scientist Linda Spilker, also with the Jet Propulsion Laboratory.
“We’re flying in a region that has never been explored before,” she said. “I wouldn’t be a bit surprised if some of the discoveries we make with Cassini during the grand finale are the best of the mission.”
(Reporting by Irene Klotz in Colorado Springs, Colo.; Editing by Steve Gorman and Sandra Maler)
These raw, unprocessed images of Saturn’s tiny moon, Pan, were taken on March 7, 2017, by NASA’s Cassini spacecraft. The flyby had a close-approach distance of 24,572 kilometers (15,268 miles).
These images are the closest images ever taken of Pan and will help to characterize its shape and geology.
NASA’s Cassini spacecraft captured the color images of Earth and the moon from its perch in the Saturn system nearly 900 million miles (1.5 billion kilometers) away. MESSENGER, the first probe to orbit Mercury, took a black-and-white image from a distance of 61 million miles (98 million kilometers) as part of a campaign to search for natural satellites of the planet.
In the Cassini images Earth and the moon appear as mere dots — Earth a pale blue and the moon a stark white, visible between Saturn’s rings. It was the first time Cassini’s highest-resolution camera captured Earth and its moon as two distinct objects.
It also marked the first time people on Earth had advance notice their planet’s portrait was being taken from interplanetary distances. NASA invited the public to celebrate by finding Saturn in their part of the sky, waving at the ringed planet and sharing pictures over the Internet. More than 20,000 people around the world participated.
“We can’t see individual continents or people in this portrait of Earth, but this pale blue dot is a succinct summary of who we were on July 19,” said Linda Spilker, Cassini project scientist, at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “Cassini’s picture reminds us how tiny our home planet is in the vastness of space, and also testifies to the ingenuity of the citizens of this tiny planet to send a robotic spacecraft so far away from home to study Saturn and take a look-back photo of Earth.”
Pictures of Earth from the outer solar system are rare because from that distance, Earth appears very close to our sun. A camera’s sensitive detectors can be damaged by looking directly at the sun, just as a human being can damage his or her retina by doing the same. Cassini was able to take this image because the sun had temporarily moved behind Saturn from the spacecraft’s point of view and most of the light was blocked.
A wide-angle image of Earth will become part of a multi-image picture, or mosaic, of Saturn’s rings, which scientists are assembling. This image is not expected to be available for several weeks because of the time-consuming challenges involved in blending images taken in changing geometry and at vastly different light levels, with faint and extraordinarily bright targets side by side.
“It thrills me to no end that people all over the world took a break from their normal activities to go outside and celebrate the interplanetary salute between robot and maker that these images represent,” said Carolyn Porco, Cassini imaging team lead at the Space Science Institute in Boulder, Colo. “The whole event underscores for me our ‘coming of age’ as planetary explorers.”
In the MESSENGER image, Earth and the moon are less than a pixel, but appear very large because they are overexposed. Long exposures are required to capture as much light as possible from potentially dim objects. Consequently, bright objects in the field of view become saturated and appear artificially large.
“That images of our planet have been acquired on a single day from two distant solar system outposts reminds us of this nation’s stunning technical accomplishments in planetary exploration,” said MESSENGER Principal Investigator Sean Solomon of Columbia University’s Lamont-Doherty Earth Observatory in Palisades, N.Y. “And because Mercury and Saturn are such different outcomes of planetary formation and evolution, these two images also highlight what is special about Earth. There’s no place like home.”
Originally published at NASA
A hidden body of water has been discovered on Saturn’s moon, Dione. Dione adds to the list of suspected subterranean oceans in our solar system.
A new study published in the Geophysical Research Letters, indicates that Saturn’s moon Dione may play host to a large subterranean ocean.
Using publicly available data from the Cassini mission to Saturn, a team from the Royal Observatory of Belgium used computer modelling techniques to uncover what they believe to be an ocean beneath the moon’s crust. The find is based on gravitational data that would only make sense if Dione contained an ocean 62 miles (or 100 kilometers) below its surface. Titan, and Enceladus – other moons of Saturn – are already believed to have water below their surfaces.
Enceladus’s gravity and shape have been explained in terms of a thick isostatic ice shell floating on a global ocean, in contradiction of the thin shell implied by librations. Here we propose a new isostatic model minimizing crustal deviatoric stress and demonstrate that gravity and shape data predict a 38 ± 4 km thick ocean beneath a 23 ± 4 km thick shell agreeing with—but independent of—libration data. Isostatic and tidal stresses are comparable in magnitude. South polar crust is only 7 ± 4 km thick, facilitating the opening of water conduits and enhancing tidal dissipation through stress concentration. Enceladus’s resonant companion, Dione, is in a similar state of minimum stress isostasy. Its gravity and shape can be explained in terms of a 99 ± 23 km thick isostatic shell overlying a 65 ± 30 km thick global ocean, thus providing the first clear evidence for a present-day ocean within Dione.
The model also shows that Dione’s ocean would surround a large rocky core 10’s of thousands of kilometers deep.
The presence of water has always been a great indication for signs of life. NASA’s “follow the water” motto echoes this sentiment. When we find water, we find the potential for microbial life.
Saturn’s moon ‘Mimas’ is getting ready to destroy a planet far-far away…
Seen above is Saturn’s moon Mimas. It’s not a battle station, it’s actually a celestial satellite and it has been battered over time to give an oddly similar appearance to the Star Wars Death Star.
Contrary to some conspiracies Mimas’ appearance did not influence or inspire the creation of the death star. Mimas was only discovered in 1980 by the Voyager spacecraft, well into production of the original films.
The similarities in the two can be attributed to a large basin on Mimas known as the Herschel crater. 139 kilometres across, it formed when an impact struck near the moon’s equator over 4.1 billion years ago.
“That’s no moon. … It’s a space station!”
Image Credit: NASA/JPL-Caltech/Space Science Institute
The rings of Saturn are one of the most intriguing features of our Solar System. New evidence from the Astrophysical Journal shows that these famous features may be younger than perceived.
Rather than appearing close to the early formation of the planet, the new research suggests that the icy rings formed near the age of the dinosaurs.
Astronomers at the Search for Extraterrestrial Intelligence (SETI) led by Matijua Cuk, took into account the orbits of Saturn’s moons and rings to find out where they were located millions of years ago.
“Moons are always changing their orbits. That’s inevitable. But that fact allows us to use computer simulations to tease out the history of Saturn’s inner moons. Doing so, we find that they were most likely born during the most recent two percent of the planet’s history.” says Cuk in a statement.
Space around Saturn is quite crowded; with over 62 moons the atmosphere is ripe for galactic chaos. Simulations from the team at SETI show that the inner moons are only roughly 100 million years old – meaning that they were born at the same time that dinosaurs inhabited our planet.
The formation of the rings has never been a mystery, only their timing. The rings were formed by the collisions of these moons as they were flung around Saturn’s orbit via the process of tidal heating. When the moons collided, dust and matter was strewn out along these orbits to produce the beautiful rings that were discovered in 1656.
“Eventually, the orbits of neighboring moons crossed, and these objects collided. From this rubble, the present set of moons and rings formed.”
Image Credit: NASA/JPL