Enceladus Lights Up Saturn’s Inner Moons

In his wonderful account of the rocket that never was (Project Orion: The True Story of the Atomic Spaceship, 2002), George Dyson discusses his father's thoughts on taking the craft to the moons of Saturn. Freeman Dyson and other Orion colleagues wanted to land on a moon to pick up propellant, but thought the moons of Jupiter were trickier than Saturn's because of the depth of the Jovian gravity well. Anyway, Enceladus was a kind of beacon, and it was there Dyson fixed his attention. George Dyson quotes Freeman on the matter: "We knew very little about the satellites in those days. Enceladus looked particularly good. It was known to have a density of .618, so it clearly had to be made of ice plus hydrocarbons, really light things; which were what you need both for biology and for propellant, so you could imagine growing your vegetables there. Five-one-thousandths g on Enceladus is a very gentle gravity, just enough so that you won't jump off." As George noted, Enceladus was a long...

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eVscope: Supporting Lucy Mission to Jupiter Trojans

Spreading scientific investigation beyond the research lab and astronomical observatory is what citizen science is all about. As we saw yesterday, projects like ExoClock are enlisting amateur volunteers to time exoplanet transits in support of the upcoming ARIEL mission. Also among such projects discussed at the ongoing EPSC-DPS joint meeting in Geneva is the eVscope digital telescope, a crowd-sourced effort from Unistellar that raised more than $3 million in its development under the direction of co-founder Franck Marchis (SETI Institute). Here again we have a useful mission tie-in. The eVscope is designed to be a compact digital instrument that can be folded into what will become an extensive network of connected telescopes. The SETI Institute recently signed an agreement with Unistellar, which Marchis now serves as chief scientific officer, to make citizen astronomy a full-fledged effort that can contribute to the Lucy mission, which will launch in 2027 to the Jupiter Trojan...

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A New Explanation for Lakes on Titan

The vast amount of data returned to Earth from the Cassini mission continues to pay off with new research angles, a process that will continue for years to come. Today we learn of a possible explanation for an odd feature of some methane-filled lakes on Saturn's moon Titan. As viewed in Cassini radar data, we can see what appear to be sharp ridges, along with cratered edges, raised rims and ramparts. Interestingly, some of the steeper ridges are considerably higher than Titan's liquid sea level. Winnipeg Lacus, a small lake near Titan's north pole, is but one example. The model currently in play about Titan's lakes is that liquid methane dissolved a bedrock of ice and solid organic compounds -- essentially creating the reservoirs which it then fills. The process is similar to karstic lakes found on Earth as the result of bodies of water dissolving surrounding limestone, dolomite or gypsum, with distinctive sinkholes and caves. But an international team of researchers headed by...

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JUICE: Targeting Three Icy Moons

Because Europa Clipper has been on my mind, what with the confirmation of its next mission phase (see Europa Clipper Moves to Next Stage), we need to continue to keep the mission in context. What is playing out is a deepening of our initial reconnaissance of the Jovian system, and the JUICE mission (Jupiter Icy Moons Explorer) is a significant part of that overall effort. The European Space Agency has the spacecraft under development, with Airbus Defence and Space as the primary contractor. We saw last week that while Europa Clipper will use flybys of Ganymede and Callisto for gravity maneuvers intended to refine its orbit, the latter two moons are not science priorities. JUICE, on the other hand, focuses on all three, each thought to house liquid water beneath the surface. JUICE is slated for a June, 2022 launch, reaching Jupiter in 2029 with the help of five gravity assists along the way, so its operations will overlap with Europa Clipper, the NASA craft launching in 2023. The...

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Going Deep into Jupiter’s Storms

Having just looked at events that may have shaped Jupiter's core, it seems a good time to note the new Hubble image of the planet, taken on June 27, 2019. A couple of things to focus on in the image below: The vast anticyclonic storm we call the Great Red Spot, about the diameter of the Earth, is evident as it rolls counterclockwise between bands of clouds moving in opposite directions toward it. We still don't know why, but the storm itself continues to shrink. Smaller storms show up vividly as white or brown ovals, some of which dissipate within hours, while others may be as long lasting as the Great Red Spot, which has dominated Jupiter's face for at least 150 years. Note the cyclone showing up south of the Spot, visible as a worm-shaped feature. You can also see other anticyclones, appearing as white ovals. Image: The NASA/ESA Hubble Space Telescope reveals the intricate, detailed beauty of Jupiter's clouds in this new image taken on 27 June 2019. It features the planet's...

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Giant Jovian Impact Could Explain Juno Data

Impacts seem to have run rampant in the early Solar System, to judge from what we keep uncovering as we survey today’s evidence. The Moon is widely considered to be the result of Earth’s impact with a Mars-class object, while Mercury’s big iron core may show what happens when a larger world is stripped of much of its mantle in another ‘big whack.’ Then there’s Uranus, spinning lopsidedly in the outer system. We also know that impacts continue to make their mark. They’re shown up on Jupiter at a fairly brisk pace, with Shoemaker-Levy striking the gas giant in 1994, and another evident impact from an asteroid earlier this month, creating a definitive flash. For that matter, we have a Hubble image from 2009 showing an impact, an expanding spot twice the length of the United States. That one was discovered by Australian amateur astronomer Anthony Wesley. Later observations allowed scientists to estimate the impactor’s diameter at 200 to 500 meters, with an explosion thousands of times...

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Europa Clipper Moves to Next Stage

Europa Clipper stays on my mind, with the intent of digging deeper into the spacecraft as development moves forward. We are talking about a craft that is by necessity radiation-tolerant as it will make a series of close flybys of Europa during its long orbit of Jupiter. 45 such flybys are in the cards, at altitudes varying from 2700 to 25 (!) kilometers, with flybys of Ganymede and Callisto in the mix as well. The latter are considered gravitational maneuvers intended to refine Europa Clipper's orbit, and while they should be productive, they are not science priorities. Image: Because Europa lies well within the harsh radiation fields surrounding Jupiter, even a radiation-hardened spacecraft in near orbit would be functional for just a few months. Studies by scientists from the Jet Propulsion Laboratory show that by performing several flybys with many months to return data, the Europa Clipper concept would enable a $2B mission to conduct the most crucial measurements of the cancelled...

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‘Dragonfly’ Chosen to Explore Titan

We've looked at a number of concepts for exploring Titan over the years, from aircraft capable of staying aloft for a year or more to balloons and boats that would float on the moon's seas. Dragonfly, the work of a team based at Johns Hopkins University's Applied Physics Laboratory in Laurel, MD, is a rotorcraft with the capability of exploiting Titan's thick atmosphere to stop, sample, and move on, shaping its investigations along the way as it explores an environment rich in targets. These are the advantages of a rover, though here we're in a landscape so exotic that it enables different tools than the ones we use on Mars. And with the success of the Martian rovers in mind, what good news that NASA has chosen Dragonfly as the next mission in its New Frontiers program. We can anticipate launch in 2026 and arrival at Titan in 2034, with a craft that will sample surface organics and examine prebiotic chemistry and potential habitability. Image: This illustration shows NASA's Dragonfly...

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Titan and Astrobiology

Night launches are spectacular, that's for sure, especially with a rocket as muscular as the SpaceX Falcon Heavy. Less spectacular, at least at this point in my life, is staying up until 0230, but delays are part of the rocket business, and what counts is a launch successful in everything but the return of the center booster (both side boosters landed upright at Cape Canaveral). Prox-1, the carrier vehicle for The Planetary Society's LightSail 2, was released at 720 kilometers, with deployment of the sail itself scheduled for July 2. While we wait for LightSail developments and also follow the fortunes of NASA's Deep Space Atomic Clock, launched as one of 24 satellites deployed by this bird, the 2019 Astrobiology Science Conference in Seattle draws attention this morning with new information about Saturn's tantalizing moon Titan. I'm still having to adapt to not having Cassini in Saturn space, but without its presence scientists are proceeding with laboratory studies that re-create...

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Into the Uranian Rings

Both DSAC (the Deep Space Atomic Clock) and LightSail 2 are on the line when a SpaceX Falcon Heavy launches on Monday evening. Both missions portend interesting developments in our push to deep space, with DSAC testing our ability to extend navigational autonomy, and LightSail 2 a solar sail that will use the power of solar photons to raise its orbit. You can follow the launch (now scheduled for 2330 Eastern (0330 UTC) on NASA Live. Also lifting off with the Falcon Heavy from the Kennedy Space Center will be almost two dozen other satellites, a nod both to the Falcon Heavy's capabilities but also to increasing spacecraft miniaturization. And speaking of interesting missions, here's something good about one whose anniversary we're about to celebrate. My friend Al Jackson, who served as astronaut trainer on the Lunar Module Simulator in the Apollo days, passed along a link to the Air-to-Ground Loop and the Flight Director's Loop from Apollo 11. Give yourself 20 minutes or so and don't...

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Ring Imagery from Cassini’s Deep Dive

Cassini's productivity at Saturn continues to provide fodder for scientific papers and encouragement for the builders of complex missions, who have seen enough data gathered by this one to guarantee continuing insights into the ringed planet for years to come. The June 14 issue of Science offers up four papers (citations below) that show results from four of the spacecraft's instruments, including startling views of the main rings. The data examined in the Science papers were gathered during Cassini's ring-grazing orbits from December, 2016 to April of 2017 as well as during the 'Grand Finale' between April and September of 2017, when Cassini flew closer than ever before to the giant planet's cloud tops. Consider the image below, showing an infrared view as captured by the spacecraft's Visible and Infrared Mapping Spectrometer (VIMS), with (at the left) the natural color view taken as a composite by Cassini's Imaging Science Subsystem. Imaging the rings in visible and near-infrared...

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What Sodium Chloride Means for Europa’s Ocean

We have priceless data on Europa from the Voyager and Galileo missions, but we're updating earlier interpretations thanks to new work with both the Hubble Space Telescope and the Keck Observatory on Mauna Kea (Hawaii). Thus the discovery that the yellow color visible on parts of Europa's surface in visible light is most likely sodium chloride (NaCl), familiar as table salt and the principal component of sea salt. That's an interesting result, given that it suggests a Europan ocean chemically more similar to Earth's than we had previously assumed. The re-thinking of the spacecraft data stems from the fact that Galileo was equipped with the Near-Infrared Mapping Spectrometer instrument, useful for analyzing the surface of a planetary body. What Galileo lacked, however, was a visible spectrometer to complement its near-infrared device. The problem: Chlorides are not apparent in the near-infrared. While Galileo had found water ice, it identified a substance believed to be magnesium...

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Triton: Insights into an Icy Surface

Al Jackson reminds me in a morning email that today is the 100th anniversary of the Arthur Eddington expedition that demonstrated the validity of Einstein’s General Relativity. The bending of starlight could be observed by looking at the apparent position of stars in the vicinity of the Sun during a solar eclipse. Eddington’s team made the requisite observations at Principe, off the west coast of Africa, and the famous New York Times headline would result: “Lights All Askew in the Heavens . . . Einstein Theory Triumphs.” Al also sent along a copy of the original paper in Philosophical Transactions of the Royal Society of London, where authorship is given as "F. W. Dyson, A. S. Eddington and C. Davidson." This created an agreeable whimsy: I imagined the evidently ageless Freeman Dyson continually traveling through time to provide his insights at major achievements like this, but the reality is that this Dyson was Frank Dyson, then Britain’s Astronomer Royal. Ron Cowen does a wonderful...

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Insulating a Plutonian Ocean

An ocean inside Pluto would have implications for many frozen moons and dwarf planets, not to mention exoplanets where conditions at the surface are, like Pluto, inimical to life as we know it. But while a Plutonian ocean has received considerable study (see, for example, Francis Nimmo's work as discussed in Pluto: Sputnik Planitia Gives Credence to Possible Ocean), working out the mechanisms for liquid ocean survival over these timeframes and conditions has proven challenging. A new paper now suggests a possible path. Shunichi Kamata of Hokkaido University led the research, which includes contributions from the Tokyo Institute of Technology, Tokushima University, Osaka University, Kobe University, and the University of California, Santa Cruz. At play are computer simulations, reported in Nature Geosciences, that offer evidence for the potential role of gas hydrates (gas clathrates) in keeping a subsurface ocean from freezing. At the center of the work, as in so much recently written...

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New Horizons: Results and Interpretations

Another reminder that the days of the lone scientist making breakthroughs in his or her solitary lab are today counterbalanced by the vast team effort required for many experiments to continue. Thus the armies involved in gravitational wave astronomy, and the demands for big money and large populations of researchers at our particle accelerators. So, too, with space exploration, as the arrival of early results from New Horizons in the journals is making clear. We now have a paper on our mission to Pluto/Charon and the Kuiper Belt that bears the stamp of more than 200 co-authors, representing 40 institutions. How could it be otherwise if we are to credit the many team members who played a role? As the New Horizons site notes: "[Mission principal investigator Alan] Stern's paper includes authors from the science, spacecraft, operations, mission design, management and communications teams, as well as collaborators, such as contributing scientist and stereo imaging specialist (and...

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Europa’s Oxygen and Aerobic Life

Few destinations in the Solar System have excited the imagination as much as Europa. Could a deep ocean beneath the ice support a biosphere utterly unlike our own? If so, we could be looking at a second emergence of life unrelated to anything on Earth, with implications for the likelihood of life throughout the cosmos. But so much depends on what happens as Europa's surface and ocean interact. Alex Tolley, a fixture here on Centauri Dreams, today looks at new work suggesting the deeply problematic nature of Europa's ocean from the standpoint of astrobiology. He also offers an entertaining glimpse at what Europa might become. by Alex Tolley Image: Plume on Europa's Surface. Credit: NASA With the abundance of newly discovered exoplanets, a fraction of them being both rocky and in their habitable zones (HZ), the excitement at finding life on such worlds is increasing. Given the ambiguous results of the attempt to detect life on Mars with the Viking experiments in 1976 and the subsequent...

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Haumea: Probing an Outer System Ring

I rarely get the chance to talk about the exotic dwarf planet Haumea, but it’s a personal favorite when it comes to the outer Solar System. That’s because of its odd shape (a bit like an American football), evidently the result of a catastrophic collision, which makes it an interesting object for close study if we can get a probe to it to examine its composition. Back in 2009, Joel Poncy and colleagues at Thales Alenia Space in France went to work on a fast orbiter mission, an extraordinarily tough challenge that would push our propulsion technologies hard. But Haumea would surely repay close study. A rapid rotator (3.9 hours, itself a likely indicator of a turbulent past), it’s a dwarf world with a ring as well as two moons, the larger of which, Hi’iaka, is some 300 kilometers in diameter. Add to this the fact that Haumea is quite reflective, indicating a surface covered with crystalline water ice. We know we can get a probe to Haumea, but orbiting it is an order of magnitude...

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Corridor of Ice Identified on Titan

What an interesting thing Titan's atmosphere turns out to be. A fine haze produced by sunlight breaking apart methane molecules settles continuously to the surface, leaving organic liquid and solid sediments. Titan also has large lakes, but these contain about a third of the necessary methane, available through evaporation, to replenish that atmosphere, which should be depleted over geological time scales. What produces Titan's supply of methane? It was to answer that question that Caitlin Griffith (University of Arizona Lunar and Planetary Laboratory) and colleagues embarked on a study of cryovolcano activity on Titan. Cryovolcanoes erupt not with molten rock but volatiles like water or methane, and thus could provide an answer if they are venting methane found in subsurface reservoirs. A feature on Titan's surface called Sotra shows cryovolcanic features that imply past icy flows. Image: A giant of a moon appears before a giant of a planet. Titan, Saturn's largest moon, measures...

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A Major Hubble Survey of the Kuiper Belt

You'll recall that well before New Horizons completed its primary mission at Pluto/Charon, the search was on for a Kuiper Belt Object that could serve as its next destination. Eventually we found Ultima Thule (2014 MU-69), from which priceless data were gathered at the beginning of January. Finding the target wasn't easy given the distances involved and the small size of the relevant objects, which is why the Hubble Space Telescope was brought into the search. The starfield in Sagittarius is crowded as we look toward galactic center, but despite the efforts of both the 8.2-meter Subaru telescope in Hawaii and the 6.5-meter Magellan telescopes in Chile, no KBOs among those found were within range of New Horizons. It was Hubble that made the difference, and Hubble which will presumably return a second target, if indeed the New Horizons team is granted an extended mission that can reach it. It's worth noting, too, that it was Hubble that helped New Horizons in its discovery of Pluto's...

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A Sparse Population of Small Kuiper Belt Objects?

One problem with learning about the Kuiper Belt is that objects out there are small and details from Earth-based imaging all too sparse. New Horizons yielded up a world of wonders with Pluto, showing us nitrogen glaciers, and mountains fully 4 kilometers tall. But even relative proximity doesn't help us in some areas. Pluto's surface has seen enough geologic activity that evidence of its impact history is sparse. Where to turn to learn what has hit it, and when? The large moon Charon may provide some answers. Unlike Pluto, its surface is relatively stable, giving us insights deep into the past. And we learn from a new paper by Kelsi Singer (SwRI) that there is a surprising lack of craters here nonetheless. The craters we do see on the two worlds were, according to the paper, formed by objects with diameters ranging from ~40 kilometers to ~300 meters, making them smaller than most KBOs we can observe with our telescopes. Thus a measure of how much in the dark we are about...

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Charter

In Centauri Dreams, Paul Gilster looks at peer-reviewed research on deep space exploration, with an eye toward interstellar possibilities. For many years this site coordinated its efforts with the Tau Zero Foundation. It now serves as an independent forum for deep space news and ideas. In the logo above, the leftmost star is Alpha Centauri, a triple system closer than any other star, and a primary target for early interstellar probes. To its right is Beta Centauri (not a part of the Alpha Centauri system), with Beta, Gamma, Delta and Epsilon Crucis, stars in the Southern Cross, visible at the far right (image courtesy of Marco Lorenzi).

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