The new Jupiter photos from JWST's Near Infrared Camera (NIRCam) are unusual, enough so that I decided to fold one into today's post. It's a pretty good fit because I had already put together most of the material I was going to use about Europa. It would have been an additional plus if Europa showed up in the image below, but even without it, note that we can see moons as small as Adrasta here. Imke de Pater (UC-Berkeley), who led the observations, noted that both tiny satellites and distant galaxies show up in the same image. And here's Thierry Fouchet, a professor at the Paris Observatory, who likewise worked on the observing effort: "This image illustrates the sensitivity and dynamic range of JWST's NIRCam instrument. It reveals the bright waves, swirls and vortices in Jupiter's atmosphere and simultaneously captures the dark ring system, 1 million times fainter than the planet, as well as the moons Amalthea and Adrastea, which are roughly 200 and 20 kilometers across,...

While we talk often about subsurface oceans in places like Europa, the mechanisms for getting through layers of ice remain problematic. We'll need a lot of data through missions like Europa Clipper and JUICE just to make the call on how thick Europa's ice is before determining which ice penetration technology is feasible. But it's exciting to see how much preliminary work is going into the issue, because the day will come when one or another icy moon yields the secrets of its ocean to a surface lander. By way of comparison, the thickest ice sheet on Earth is said to reach close to 5,000 meters. This is at the Astrolabe Subglacial Basin, which lies at the southern end of Antarctica's Adélie Coast. Here we have glacial ice covering continental crust, as opposed to ice atop an ocean (although there appears to be an actively circulating groundwater system, which has been recently mapped in West Antarctica). The deepest bore into this ice has been 2,152 meters, a 63 hour continuous...

I get an eerie feeling when I look at spacecraft before they launch (not that I get many opportunities to do that, at least in person). But seeing the Spirit and Opportunity rovers on the ground at JPL just before their shipment to Florida was an experience that has stayed with me, as I pondered how something built by human hands would soon be exploring another world. I suppose the people who do these things at the Johns Hopkins Applied Physics Laboratory and the Jet Propulsion Laboratory itself get used to the feeling. For me, though, the old-fashioned 'sense of wonder' kicks in long and hard, as it did when Europa Clipper arrived recently at JPL. Not that the spacecraft is by any means complete, but its main body has been delivered to the Pasadena site, where it will see final assembly and testing over a two-year period. Here I fall back on the specs to note that this is the largest NASA spacecraft ever designed for exploration of another planet. It's about the size of an SUV when...

I’m always interested in studies that cut across conventional boundaries, capturing new insights by applying data from what had appeared, at first glance, to be unrelated disciplines. Thus the news that the ice shell of Europa may turn out to be far more dynamic than we have previously considered is interesting in itself, given the implications for life in the Jovian moon’s ocean, but also compelling because it draws on a study that focused on Greenland and originally sought to measure climate change. The background here is that the Galileo mission that gave us our best views of Europa’s surface so far showed us that there are ‘double ridges’ on the moon. In fact, these ridge pairs flanked by a trough running between them are among the most common landforms on a surface packed with troughs, bands and chaos terrain. The researchers, led by Stanford PhD student Riley Culberg, found them oddly familiar. Culberg, whose field is electrical engineering (that multidisciplinary effect again)...

A spray of organic molecules and ice particles bursting out of an outer system moon is an unforgettable sight, as Cassini showed us at Enceladus. Finding something similar at Europa would be a major help for future missions there, given the opportunity to sample a subsurface ocean that is perhaps as deep as 160 kilometers. But Lynnae Quick (NASA GSFC), who works on the science team that produced the Europa Imaging System cameras that will fly on the Europa Clipper mission, offers a cautionary note: "A lot of people think Europa is going to be Enceladus 2.0, with plumes constantly spraying from the surface. But we can't look at it that way; Europa is a totally different beast." A good thing that Europa Clipper can produce evidence of conditions beneath the ice without the need for plumes when it begins its explorations in 2031. In fact, adds Quick, every instrument aboard the spacecraft has its own role to play in the study of that global ocean. Still, potential plumes are too...

Juno has worked wonders for our knowledge of Jupiter, but we continue to rely on Hubble observations and still helpful imagery from Galileo as we study the giant planet's intriguing moon Europa, anticipating the arrival of Europa Clipper and the European Space Agency's Jupiter Icy Moons Explorer (JUICE) at the end of the decade. The great question is whether life can exist beneath the ice, and the evidence of plume activity, first found in 2013 in Hubble data, is encouraging in some ways more than others. A mission to Saturn's moon Enceladus can rely on geysers in a particular place -- the Tiger Stripes at the south pole -- and on geysers that are frequent. At Europa, predicting where and when a plume will burst forth is all but a black art. How do we sample a Europan plume? Image: Will we one day see Europa through the eyes of a (well-shielded) lander? Credit: NASA. While contemplating that question, we push ahead with other analyses that help us characterize this unusual place. A...

Something interesting always comes out of the Europlanet Science Congress (probably better known to Centauri Dreams readers under its former name, the European Planetary Science Congress), and this year is no exception. This is the largest planetary science meeting in Europe, normally drawing about 1000 participants, though last year and this year as well have been virtual meetings, the latter ongoing as I write this and running until September 24. As the conference proceeds, my eye was drawn to a study by Tristan Guillot on the ice giants Uranus and Neptune, targets of (let’s hope) future space missions that can help us resolve the differences between this class of world and gas giants like Jupiter and Saturn. Guillot (CNRS, Laboratoire Lagrange, Nice) targets the odd fact that both of these planets have recently been found to be deficient in ammonia in their atmospheres as compared to the gas giants. Astronomers are puzzled because other compounds such as methane, found in the...

TAOS II is the Transneptunian Automated Occultation Survey, designed to spot comets deep in our Solar System. It may also be able to detect comets of the interstellar variety, of which we thus far have only one incontrovertible example, 2I/Borisov. And TAOS II, as well as the Vera C. Rubin Observatory (both are slated for first light within a year or so) could have a lot to work with, if a new study from Amir Siraj and Avi Loeb (Center for Astrophysics | Harvard & Smithsonian) is correct in its findings. I cite Borisov as thus far unique in being an interstellar comet because the cometary status of ‘Oumuamua is still in play. On my way to looking at his paper on Borisov, I had an email exchange with Avi Loeb, from which this: Observations with the Spitzer Space Telescope of `Oumuamua placed very tight limits on carbon-based molecules in its vicinity, implying that it was not made of carbon or oxygen. This led to suggestions that perhaps it is made of pure hydrogen or pure nitrogen,...

Rotorcraft have certainly been in the news lately, with Ingenuity, the Mars helicopter, commanding our attention. The Dragonfly mission to Titan involves a far more complex rotorcraft capable of visiting numerous destinations on the surface. In fact, Dragonfly makes use of eight rotors and depends upon an atmosphere more helpful than what Ingenuity has to work with on Mars. Titan's atmosphere is four times denser than what we have on Earth, allowing Dragonfly to move its entire science payload from one location to another as it examines surface landing zones while operating on a world whose gravity is but one-seventh that of Earth. I want to call your attention to the publication of the science team that just appeared in the Planetary Science Journal, because it lays out the rationale for the various decisions made thus far about operations on and above Titan's surface. It's a straightforward, interesting read, and makes clear how much work we have to do here. Yes, we had Cassini for...

Seeing spacecraft coming together is always exciting, and when it comes to Europa Clipper, what grabs my attention first is the radiation containment hardware. This is a hostile environment even for a craft that will attempt no landing, for flybys take sensitive electronics into the powerful radiation environment of Jupiter's magnetosphere. 20,000 times stronger than Earth's, Jupiter's magnetic field creates a magnetosphere that affects the solar wind fully three million kilometers before it even reaches the planet, trapping charged particles from the Sun as well as Io. We have to protect Europa Clipper from the intense radiation emerging out of all this, and in the image below you can see what the craft's engineers have come up with. Now nearing completion at the Jet Propulsion Laboratory, the aluminum radiation vault will ultimately be attached to the top of the spacecraft's propulsion module, connecting via kilometers of cabling that will allow its power box and computer to...

Hubble observations from the past two decades have been recently re-examined as a way of investigating what is happening in the tenuous atmosphere of Ganymede, the largest moon in the Solar System. It was in 1998 that the telescope’s Space Telescope Imaging Spectrograph took the first images of Ganymede at ultraviolet wavelengths, showing auroral bands -- ribbons of electrified gas -- that reinforced earlier evidence that the moon had a weak magnetic field. Now we have news of sublimated water vapor within the atmosphere, an earlier prediction now verified. Ganymede’s atmosphere, such as it is, is the result of charged particles and solar radiation eroding its icy surface, producing both molecular (02) and atomic oxygen (0) as well as H20, with the molecular oxygen long thought to be the most abundant constituent overall. Surface temperatures are as extreme as you would expect, roughly between 80 K and 150 K (-193 °C to -123 °C). In 2018, a team led by Lorenz Roth (KTH Royal...

Our recent discussion about Europa (Europa: Below the Impact Zone) has me thinking about those tempting Galilean moons and the problems they present for exploration. With a magnetic field 20,000 times stronger than Earth’s, Jupiter is a radiation generator. Worlds like Europa may well have a sanctuary for life beneath the ice, but exploring the surface will demand powerful radiation shielding for sensitive equipment, not to mention the problem of trying to protect a fragile human in that environment. Radiation at Europa’s surface is about 5.4 Sv (540 rem), although to be sure it seems to vary, with the highest radiation areas being found near the equator, lessening toward the poles. In human terms, that’s 1800 times the average annual sea-level dose. Europa is clearly a place for robotic exploration rather than astronaut boots on the ground. Jupiter offers up an environment where the solar wind, hurling electrically charged particles at ever-shifting velocities, interacts with the...

Yesterday we looked at the behavior of ice on Enceladus, a key to making long range plans for a lander there. But as we saw with Kira Olsen and team’s work, learning about the nature of ice on worlds with interior oceans has implications for other ice giant moons. This morning we look at the hellish surface environment of Europa, as high-energy radiation sleets down inside Jupiter’s magnetic field. Europa’s surface radiation will complicate operations there and demand extensive shielding for any lander. But below the ice, that interior ocean should be shielded and warm enough to offer the possibility of life. With Europa Clipper on pace for a 2024 launch, we need to ask how the surface ice has been shaped and where we might find biosignatures that could have been churned up from below. Tidal stresses on the ice leading to fracture are one way to force material up, but small impacts from above -- debris in the Jovian system -- also roil the surface. If we’re looking for potential...

We could do with more information about how ice behaves on a gas giant’s moon. We’ll need this knowledge to understand the behavior of crustal ice on places like Europa and Enceladus, where oceans may provide sub-surface venues for life. One approach into the subject is to look at ice right here on Earth; specifically, the Antarctic ice shelves. A new study out of NASA’s Goddard Space Flight Center applies a model based on Antarctic data to the fractured south pole of Enceladus, probing tidally driven stress and seismic activity within an ice shell. We assume that tidal stresses produced by the moon’s interactions with Saturn, as well as the planet’s larger moons, keep the interior of Enceladus warm, while at the same time producing cracks and accounting for the geysers of water vapor Cassini found erupting from the so-called ‘Tiger Stripes’ (fractures) at the southern pole. The tides of Enceladus must be massive, and learning about the seismic activity they induce offers a key to...

The Juno spacecraft swings by Ganymede today, coming within 1,038 kilometers of the largest moon of Jupiter. We have to look back over twenty years to see such a close approach to Ganymede, that one conducted by the Galileo probe in 2000. Juno seems to be one of those gifts that keeps on giving, rewarding us now with new data on Ganymede's composition, tenuous ionosphere, magnetosphere and icy surface, likely a shell over an underlying ocean. Scott Bolton (SwRI) is Juno's principal investigator: "Juno carries a suite of sensitive instruments capable of seeing Ganymede in ways never before possible. By flying so close, we will bring the exploration of Ganymede into the 21st century, both complementing future missions with our unique sensors and helping prepare for the next generation of missions to the Jovian system - NASA's Europa Clipper and ESA's [European Space Agency's] JUpiter ICy moons Explorer [JUICE] mission." Image: Left to right: The mosaic and geologic maps of Jupiter's...

The first thing to say about the image below is that it fills me with anticipation for the imagery that Europa Clipper will acquire when it travels to the Jovian moon later this decade (arrival in 2030, according to current planning). This is a Galileo image taken in 1996, the subject of intense study, as have been all the Europa images, ever since. How much interaction does Europa's subsurface ocean have with the icy crust? We can't say for sure how much is going on now, but images like these show how much fracturing and re-formation there has been in the past. In any event, fresh data from Europa Clipper should give us entirely new insights. Image: Enhanced image of a small region of the thin, disrupted ice crust on Jupiter's moon Europa taken in 1996 by NASA's Galileo spacecraft. Image Source: NASA. Beyond that, though, there is another story with Europa implications that is being investigated by scientists at Oak Ridge National Laboratory, an installation under the aegis of the...

It's easy to forget how large our space probes have been. A replica of the Galileo probe during at the Jet Propulsion Laboratory can startle at first glance. The spacecraft was 5.3 meters high (17 feet), but an extended magnetometer boom telescoped out to 11 meters (36 feet). Not exactly the starship Enterprise, of course, but striking when you're standing there looking up at the probe and pondering what it took to deliver this entire package to Jupiter orbit in the 1990s. The same feeling settles in this morning with news out of Lockheed Martin Space, where in both December 2020 and February of 2021 final deployment tests were conducted on the solar arrays that will fly aboard the Lucy mission. Scheduled for launch this fall (the launch window opens on October 16), Lucy is to make a 12-year reconnaissance of the Trojan asteroids of Jupiter. Given that energy from the Sun is inversely proportional to the square of the distance, Lucy in Jupiter space will receive only 1/27th of the...

Just as Earth’s atmosphere scatters light from the Sun, both Jupiter and Saturn scatter X-rays produced by our star. In a new study using data from the Chandra X-ray Observatory, we now learn that Uranus likewise scatters X-rays, but with an interesting twist. For there is a hint -- and only a hint -- that scattering is only one of the processes at work here, and that could produce insights into a system that thus far we have been able to study up close only once, through the flyby of Voyager 2. As the paper on this work notes: “These fluxes exceed expectations from scattered solar emission alone.” Just what is going on here will demand further work. William Dunn (University College London) is lead author of the paper, which includes co-authors from an international team working with Chandra data from 2002 and 2017. In the image below, the X-ray data from Chandra is superimposed upon a 2004 observation of Uranus from the Keck telescope, which shows the planet at essentially the same...

New thinking about the shape of the ice shell on Enceladus raises the interesting possibility that the ocean believed to lie beneath is churning with currents. That would be a departure from the accepted view that the ocean -- thought to be 30 kilometers deep or more, as opposed to Earth's average of 3.6 kilometers -- is relatively homogenous. Remember, this is a body of water buried beneath perhaps 20 kilometers of ice, locked within a moon that is 500 kilometers in diameter. We know it's there because a 2014 flyby of the Cassini Saturn orbiter collected data on geyser activity erupting through the striking fissures in the south polar ice. That immediately put Enceladus high on the list of astrobiologically interesting targets along with, of course, Jupiter's moon Europa. Image: A masterpiece of deep time and wrenching gravity, the tortured surface of Saturn's moon Enceladus and its ongoing geologic activity tell the story of the ancient and present struggles of one tiny world. A...

The news that Ingenuity, the helicopter aboard NASA's Perseverance rover, contains a swathe of fabric from the 1903 Wright Flyer underscores the conflation in time I've been feeling all week, ever since looking at the images below. The first, released by the New Horizons mission team, shows a speck to the right of Pluto. This is 486958 Arrokoth, the Kuiper Belt Object visited by New Horizons at the beginning of 2019 and superimposed in the Pluto image just for scale. Image: The main exploration targets of New Horizons: Pluto (2015) and the much smaller Arrokoth (2019), to scale. Other exploration targets included Pluto's five moons. Credit: NASA/Johns Hopkins APL/Southwest Research Institute. The point is strikingly made: Pluto itself, which had been no more than a speck in our field of view in 1930, when what was deemed the ninth planet was discovered, has now become a world, and even the tiny Arrokoth is a well imaged object, the farthest ever visited by a spacecraft. Such...