Scientists at the European Southern Observatory are describing newly observed wind processes on Jupiter as "a unique meteorological beast." I like the phrase and can see its application to the 1450 kilometer per hour jets they've uncovered near Jupiter's poles. Just how they made this detection is fascinating in its own right, since they drew on a spectacular natural event, the 1994 collision of comet Shoemaker-Levy 9 with the planet, to deduce current conditions. The molecules that were produced in that impact are the lever that moves the investigation, which is headed by Thibault Cavalié (Laboratoire d'Astrophysique de Bordeaux). Image: This image shows an artist's impression of winds in Jupiter's stratosphere near the planet's south pole, with the blue lines representing wind speeds. These lines are superimposed on a real image of Jupiter, taken by the JunoCam imager aboard NASA's Juno spacecraft. Jupiter's famous bands of clouds are located in the lower atmosphere, where...

The orbital interactions between objects in a stellar system result in all kinds of interesting effects, a celestial pinball machine that sometimes flings planets outward to wander alone among the stars. Gas giants can be pulled from more distant orbits into a broiling proximity to their star. But the object known as P/2019 LD2 has a special interest because its interactions are happening in a tight time frame even as we observe them. We could call P/2019 LD2 a 'comet-like object,' because it sometimes acts like an asteroid, sometimes like a comet. It is in fact a Centaur, one of that group of outer system objects that only become active as they move into the inner system. We're watching a transition from Centaur to Jupiter family comet mediated by the gradually warming environment. This one evidently swung close to Jupiter roughly two years ago, to be flung by the giant planet's gravity toward the Trojan asteroid group that leads Jupiter in its orbit by some 700 million kilometers....

I can remember when I first read about the experiment that Stanley Miller and Harold Urey performed at the University of Chicago in 1952 to see if organic molecules could be produced under conditions like those of the early Earth. It was a test of abiogenesis, though that wasn't a word I knew at the time. Somewhere around 5th grade, I was a kid reading a book whose title has long escaped me, but the thought that scientists could re-create the atmosphere the way it was billions of years ago seized my imagination. Never mind that exactly what was in that atmosphere has been controversial. What thrilled me was the attempt to reproduce something long gone -- billions of years gone -- and to experiment to find out what it might produce. I just finished Samanth Subramanian's elegant biography of J. B. S. Haldane, the polymathic geneticist, mathematician, physiologist (and too much more to list here), whose work on the chemical formation of life was strongly supported by the Miller and Urey...

One thing is certain about the now confirmed object that is being described as the most distant ever observed in our Solar System. We’ll just be getting used to using the official designation of 2018 AG37 (bestowed by the Minor Planet Center according to IAU protocol) when it will be given an official name, just as 2003 VB12 was transformed into Sedna and 2003 UB313 became Eris. It’s got a charming nickname, though, the jesting title “Farfarout.” I assume the latter comes straight from the discovery team, and it’s a natural because the previous most distant object, found in 2018, was dubbed “Farout” by the same team of astronomers. That team includes Scott Sheppard (Carnegie Institution for Science), Chad Trujillo (Northern Arizona University) and David Tholen (University of Hawai?i). Farout, by the way, has the IAU designation 2018 VG18, but has not to my knowledge received an official name. Trans-Neptunian objects can be useful for investigating the gravitational effects of...

There was a time when the Solar System seemed relatively well defined, with nine planets including Pluto and an asteroid belt that orbited in a niche between Mars and Jupiter. These days, in addition to the Kuiper Belt and Oort Cloud, we have to factor in all the objects that move on unusual orbits. We have a mission in the works, called Lucy, to the Jupiter Trojans, those asteroids that share the giant planet's orbit around the Sun. And today we're looking at Centaurs, which cross the orbits of giant planets and are in rapid dynamical evolution. The subject comes up because a newly discovered comet -- 2019 LD2 (ATLAS) -- is not only a Centaur, but a Centaur that is rapidly on its way to becoming another class of object, a Jupiter Family Comet (JFC). The latter are short-period comets with an orbital period of less than 20 years, largely under the influence of Jupiter. A paper by Jordan Steckloff (Planetary Science Institute) and team lays out the case: Centaurs are objects in...

How salty should we expect the ice on Europa’s surface to be? It would be helpful to know, because the salinity of the surface will be a factor in how transparent the ice shell is to radar waves. Europa Clipper will fly with an instrument called REASON -- Radar for Europa Assessment and Sounding: Ocean to Near-surface -- which will be investigating both the surface ice and the ocean beneath. Recent research, in which its principal investigator, Don Blankenship (University of Texas), is involved is offering insights into the salinity of the ice. Here’s a bit of background on REASON from a NASA page on Europa Clipper: Depending on their wavelength, radio waves can either bounce off or penetrate different materials. REASON will use high frequency (HF) and very high frequency (VHF) radio signals to penetrate up to 18 miles (30 kilometers) into Europa’s ice to look for the moon’s suspected ocean, measure ice thickness, and better understand the icy shell's structure. The instrument will...

When it comes to Europa, it's the surface that counts as we try to learn more about the ocean beneath. Maybe one day we'll be able to get some kind of probe through the ice, but for now we have to think about things like upwellings of water that percolate up through cracks in the frozen landscape, and unusual areas like Europa's 'chaos' terrain. Here, fractures and evident 'rafts' of ice show disruptions where the icy surface of the moon experiences Jupiter's tidal effects. Image: The surface of Jupiter's moon Europa features a widely varied landscape, including ridges, bands, small rounded domes and disrupted spaces that geologists called "chaos terrain." This newly reprocessed image, along with two others along the same longitude, was taken by NASA's Galileo spacecraft on Sept. 26, 1998, and reveals details of diverse surface features on Europa. Credit: NASA/JPL-Caltech/SETI Institute. What kind of materials might we find frozen into the cracks and grooves of such terrain? Europa...

The days when scientists assumed our Solar System would be something of a template for planetary systems elsewhere are long past. The issue now is to delve deeper into system architectures to figure out what happens in their infancy and how they evolve. Working backward from today's Solar System is one way to approach the problem. Thus Matt Clement (Carnegie Institution for Science), who has led a recent study into the formation of Jupiter and Saturn, hoping to determine how they wound up in their present orbits. Says Clement: "We now know that there are thousands of planetary systems in our Milky Way galaxy alone. But it turns out that the arrangement of planets in our own Solar System is highly unusual, so we are using models to reverse engineer and replicate its formative processes. This is a bit like trying to figure out what happened in a car crash after the fact--how fast were the cars going, in what directions, and so on." Image: New work led by Carnegie's Matt Clement reveals...

What accounts for the differences in Titan's craters? It will be helpful from an operational standpoint to learn more, for in 2027 the Dragonfly mission will launch, with Selk Crater a target. An equatorial dune crater, Selk is completely covered in a dark organic material, unlike other higher-latitude craters on the Saturnian moon that are scoured and cleansed by rain. We have learned from data produced by Cassini's Visible and Infrared Mapping Spectrometer (VIMS) that Titan's craters come in two kinds. Equatorial craters like Selk occur in dune fields and consist mostly of organics. Mid-latitude craters show a mix of organics and water ice. The organic material generated by processes in Titan's thick atmosphere is sand-like, piling up in equatorial regions but being eroded at the higher, wetter latitudes. For Dragonfly's purposes, we want to know more about how the methane rain and streams affect the surface as we fine-tune the data analysis and monitoring techniques to be used in...

Now and then people mention that our Pioneers and Voyagers made it through the Kuiper Belt on their long journey toward system's edge, though unfortunately without operational cameras to record what they saw. A missed opportunity? Not really. Think about how long it took to find a Kuiper Belt Object like Arrokoth, the first one ever seen close up thanks to the mighty work of the New Horizons team. Without a major search to find a target, a craft passing through the Kuiper Belt is almost certainly going to encounter no objects whatsoever within range to record the details. For now, Arrokoth, the object once known as Ultima Thule before running afoul of our times, has to serve as our example of what can emerge in this distant region, and an odd object it is. When its shape is compared to a flattened snowman, as it often is, the real story is in the word 'flattened.' How does this roughly 30-kilometer object emerge in the shape it's in, and under what conditions was it spawned out there...

A second ecliptic? What an interesting notion, referred to in a new paper from Arika Higuchi as an 'empty ecliptic,' constituting a second alignment plane for the Solar System. This is lively stuff, examined in a new paper in the Astronomical Journal that focuses on the aphelia of long-period comets, the points where they are farthest from the Sun in their orbit. The solutions arrived at through the paper's dense mathematics show that the aphelia fall close to one or the other of the ecliptic planes, and offer insights into comet formation. Higuchi (University of Occupational and Environmental Health, Japan) has previously been a part of the National Astronomical Observatory of Japan's RISE project, RISE standing for Research of Interior Structure and Evolution of solar system bodies. Her work on the orbital evolution of planetesimals goes back at least to 2007 in a paper on the formation of the Oort Cloud, considering the effects of interactions with the 'galactic tide,' a reference...

The presence of the always intriguing Titan brings into sharper focus recent work on the age of the moons of Saturn conducted by Samuel Bell (Planetary Science Institute). Given the active weathering visible on Titan, the assumption that it is at least four billion years old, which draws on earlier work on the age of Saturn’s moon system, is challenged by the lakes, mountains, riverbeds and dunes we see in the Cassini data. Bell argues that an older Titan would have to be one with an extremely low erosion rate and minimal resurfacing. But maybe Titan is younger than we’ve thought. Bell assembles the context of Titan in the overall system at Saturn by studying the cratering rate on the various moons. Determining the age of a planetary surface -- think Mars or the Moon -- is generally done by counting the impact craters and weighing this against the cratering rate. At Saturn, the problem is that the cratering rate is not known. It would be one value if, as previous work has assumed,...

One of my better memories involving space exploration is getting the chance to be at the Jet Propulsion Laboratory to see the Mars rovers Spirit and Opportunity just days before they were shipped off to Florida for their eventual launch. Being near an object that, though crafted by human hands, is about to be a presence on another world is an unusual experience, one that made me reflect on artifacts from deep in the human past and their excavation by archaeologists today. Will future humans one day recover our early robotic explorers? That reflection was prompted by news from JPL that engineers have delivered the key elements of a critical ice-penetrating radar instrument for the European Space Agency's mission to three of Jupiter's icy moons. JUICE -- JUpiter ICy moons Explorer -- is scheduled for a launch in 2022, with plans to orbit Jupiter for three years, involving multiple flybys of both Europa and Callisto, with eventual orbital insertion at Ganymede. Analyses of the interiors...

Io, Jupiter’s large, inner Galilean moon, is the very definition of a tortured surface, as seen in the image below, taken by the Galileo spacecraft in 1997. Discovering volcanic activity -- and plenty of it -- on Io was one of the early Voyager surprises, even if it didn’t surprise astrophysicist Stanton Peale (UC-Santa Barbara) and colleagues, who predicted the phenomenon in a paper published shortly before Voyager 1’s encounter. We now know that Io is home to over 400 active volcanoes, making it the most geologically active body in the Solar System. We’re a long way from the Sun here, but we know to ascribe Io’s surface upheaval to tidal heating forced by the presence of Jupiter as the gravitational forces involved stretch and squeeze not just Io but, of course, Europa, Ganymede and Callisto, all of them interesting because of the possibility of liquid oceans beneath the surface. Io is close enough to the giant world that rock can be melted into magma, but it’s the ice under more...

When we looked earlier this week at the Solaris mission, a concept designed to study the Sun's polar regions, I commented on another early concept called the Auroral Reconstruction CubeSwarm (ARCS). The mission intrigued me because it consisted of CubeSats in swarm formation, working together with numerous ground observatories, to study the Earth's auroras. The paradigm of miniaturization, low cost and creative design surfaces yet again in Janus, a proposal out of the University of Colorado at Boulder and Lockheed Martin that would involve twin spacecraft studying twin targets, the binary asteroids 1996 FG3 and 1991 VH. Daniel Scheeres (CU-Boulder) is principal investigator for Janus, the plan being for the university to handle the analysis of data and images from the mission, with Lockheed Martin building and operating the two spacecraft. It should be a familiar role for both entities, as Lockheed Martin supports operations for OSIRIS-REx at asteroid Bennu, while Scheeres leads the...

A hypothesis about an astronomical object snaps into sharper detail when it can be tested. Thus the new findings on Europa and the movements of the ice shell that covers its ocean, which are the subject of a paper in Geophysical Research Letters. The work of Paul Schenk (Lunar and Planetary Institute, Houston) and colleagues, the paper argues that the shell has rotated by about 70 degrees during the last several million years. Clearly, such movement can only happen with a shell floating freely over a liquid ocean beneath, and Europa Clipper should be able to tell us more. Remember, we are talking about a geologically young surface on this Jovian moon, as indicated by, among other things, the relative smoothness of the terrain and the paucity of impact craters. All that is consistent with ice in motion in one way or another. Schenk's team homes in on large global-scale circular patterns that can be made out by reference to Galileo and Voyager data, previously identified features that...

Have a look at what two of our older spacecraft saw on Jupiter's giant moon Ganymede, a world that will snap into much greater focus once the JUICE mission arrives in 2029. The JUpiter ICy moons Explorer is slated for launch in 2022, with the intention of studying Ganymede, Callisto and Europa. But it's Ganymede that will get the lion's share of the attention from this European Space Agency effort as JUICE slides into orbit around the moon in 2032, marking the first time a spacecraft has orbited a moon circling a planet other than our own. Image: Images of Ganymede's surface taken by Voyager 2 (left) and Galileo (right). The Dark Terrain and Bright Terrain areas can be recognized, with concurrent furrows present in the Dark Terrains. Credit: NASA. We looked at more recent Juno views of Ganymede just last month (see Glimpses of Ganymede), along with interesting results from its most recent flyby on disruptions in the crystalline structure of the moon's north polar ice due to incoming...

A great part of the excitement of scientific discovery is not knowing what will emerge when you take data. Our space missions have proven that time and again, and I have no doubt that as we tighten the resolution on future telescopes, we’ll find things that defy many an accepted theory. NASA’s Stardust mission reflects the phenomenon. Designed as a comet sample return, Stardust is now providing information about the migration of materials in the primordial Solar System, which may point toward a phenomenon more widespread than earlier believed. Thus the work of Devin Schrader and Jemma Davidson (University of Arizona Center for Meteorite Studies). Working with colleagues at the Smithsonian Institution’s National Museum of Natural History, the University of Hawai?i at M?noa, Washington University in St. Louis, and Harvard University, the duo have produced evidence that at least fragmentary materials in the inner Solar System crossed what is often called the ‘Jupiter Gap’ and moved much...

We learned some time ago from the Dawn mission just how interesting a place Ceres is. If you're wanting to dig into the latest research on the dwarf planet, as it is now termed, be aware that a collection of papers has appeared in Nature Astronomy, Nature Geoscience and Nature Communications, all published on August 10. These analyze data gathered during Dawn's second extended mission (XM2) phase, which closed with a series of low orbits as close as 35 kilometers from the surface. Rather than listing these papers separately, I'll just offer this link to the entire collection at nature.com. The upshot is that we're continuing to learn about a small world that remains surprisingly active. Let's home in on cryovolcanism, which leverages the temperature differential between a frozen world's interior water and its frigid surface to produce ejections. These are becoming almost common -- think Enceladus, for example, and then remember what Voyager saw at Triton. The thinking has been that...

Have a look at Ganymede as seen by the Juno spacecraft on December 26, 2019, the day after Christmas (and a day and time that now seems impossibly distant given all that has been going on closer to home). Jupiter's largest moon is also the largest satellite in the Solar System, bigger even than Titan, and 26% larger than the planet Mercury, though far less massive. Our view comes courtesy of Juno's Jovian Infrared Auroral Mapper (JIRAM) instrument. Image: These images were taken by the JIRAM instrument aboard NASA's Juno spacecraft on Dec. 26, 2019, providing the first infrared mapping of Ganymede's northern frontier. Frozen water molecules detected at both poles have no appreciable order to their arrangement and a different infrared signature than ice at the equator. Credit: NASA/JPL-Caltech/SwRI/ASI/INAF/JIRAM. Three-quarters the size of Mars, Ganymede began turning up in science fiction early in that genre's development, as in Stanley Weinbaum's "Tidal Moon," which ran in the...